MAX8903JETI+T [MAXIM]
Power Supply Support Circuit, Fixed, 1 Channel, BICMOS, 4 X 4 MM, 0.75 MM HEIGHT, ROHS COMPLIANT, MO-220WGGE, TQFN-28;
| 型号： | MAX8903JETI+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Power Supply Support Circuit, Fixed, 1 Channel, BICMOS, 4 X 4 MM, 0.75 MM HEIGHT, ROHS COMPLIANT, MO-220WGGE, TQFN-28 |
| 文件： | 总76页 (文件大小：3906K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4410; Rev 5; 9/11
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
概述
特性
S 高效DC-DC转换器，无需散热器
MAX8903A-MAX8903E/MAX8903G/MAX8903H/
+
MAX8903J/MAX8903N/MAX8903Y是集成的单节Li 电池
S 4MHz开关频率，允许使用小尺寸外部元件
S 立即开启—能够在无电池/低电池电压下工作
充电器和Smart Power SelectorTM (智能电源选择器)，提
供双电源输入(交流适配器和USB)。开关模式充电器工作
在较高的开关频率，可以省去散热器并允许使用小尺寸
外部元件。该器件可采用独立的USB电源或交流适配器供
电，也可以用一个输入端接收两路电源输入。芯片集成了
所有充电功能和用于切换电池、外部电源、负载的功率开
关。无需外部MOSFET、反向保护二极管和检流电阻。
S 两路限流输入—交流适配器或USB
适配器/USB/电池供电自动切换，支持瞬变负载
50mΩ系统至电池开关导通电阻
支持USB规范
S 热敏电阻检测
MAX8903_优化工作于智能化电源管理模式，可充分利用
有限的USB或适配器电源的供电能力。电池充电电流和
SYS输出限流均可独立设置。在保证系统供电的前提下
为电池充电。充电电流和SYS输出限流可设置在最高2A，
USB输入限流可设置在100mA或500mA。输入选择电路
能够自动地将系统供电电源从电池切换至外部电源。器件
工作在4.15V至16V直流输入电压范围，输入端具有高达
20V的保护；USB输入范围为4.1V至6.3V，输入端具有最
高8V保护。
S 集成检流电阻
S 无需外部MOSFET或二极管
S 4.1V至16V输入工作电压范围
定购信息
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
MAX8903AETI+T
MAX8903BETI+T
MAX8903CETI+T
MAX8903DETI+T
MAX8903EETI+T
MAX8903GETI+T
MAX8903HETI+T
MAX8903JETI+T
MAX8903NETI+T
MAX8903YETI+T
未接输入电源时，MAX8903_内部电路可以阻止电流从电
池、系统倒灌到直流电源、USB输入。其它功能包括：预
充检测及定时器、快充定时器、过压保护、充电状态指
示和故障指示输出、电源就绪监视器以及电池热敏电阻
检测等。此外，片内热管理电路可以根据需要降低电池
充电速率或交流适配器的充电电流，以防止充电器过热。
MAX8903_采用4mm x 4mm、28引脚薄型QFN封装。
不同版本的MAX8903_提高了设计灵活性，便于选择不
同的系统电源电压、电池预检验门限和电池满充电压。
MAX8903B/MAX8903E/MAX8903G的电池检测功能还包
含供电使能控制，详细信息请参考选型指南部分。
+表示无铅(Pb)/符合RoHS标准的封装。
*EP = 裸焊盘。
T = 卷带包装。
应用
典型工作电路
PDA、掌上电脑和
无线手持装置
便携式多媒体播放器
移动互联网设备
超便携移动PC
AC
ADAPTER
OR USB
LX
CS
个人导航设备
智能蜂窝电话
DC
SYS
LOAD
CURRENT
CHARGE
CURRENT
CHARGE
AND
SYSTEM
LOAD
SYS LOAD
SWITCH
PWM
STEP-DOWN
BAT
BATTERY
USB
USB
MAX8903_
GND
选型指南在数据资料的最后给出。
Smart Power Selector是Maxim Integrated Products, Inc.的商标。
引脚配置在数据资料的最后给出。
ꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀꢀ Maxim Integrated Products
1
本文是英文数据资料的译文，文中可能存在翻译上的不准确或错误。如需进一步确认，请在您的设计中参考英文资料。
有关价格、供货及订购信息，请联络Maxim亚洲销售中心：10800 852 1249 (北中国区)，10800 152 1249 (南中国区)，
或访问Maxim的中文网站：china.maxim-ic.com。
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
ABSOLUTE MAXIMUM RATINGS
DC, LX to GND .......................................................-0.3V to +20V
LX Continuous Current (total in two pins)......................2.4A
CS Continuous Current (total in two pins) ......................2.4A
SYS Continuous Current (total in two pins) .......................3A
BAT Continuous Current (total in two pins) .......................3A
RMS
RMS
RMS
RMS
DCM to GND .............................................-0.3V to (V
+ 0.3V)
DC
DC to SYS .................................................................-6V to +20V
BST to GND ...........................................................-0.3V to +26V
BST TO LX................................................................-0.3V to +6V
USB to GND .............................................................-0.3V to +9V
USB to SYS..................................................................-6V to +9V
VL to GND ................................................................-0.3V to +6V
VL Short Circuit to GND .............................................Continuous
Continuous Power Dissipation (T = +70NC)
A
28-Pin Thin QFN-EP
Multilayer (derate 28.6mW/°C above +70NC) ..........2286mW
28-Pin Thin QFN-EP
THM, IDC, ISET, CT to GND........................-0.3V to (V + 0.3V)
DOK, FLT, CEN, UOK, CHG, USUS,
BAT, SYS, IUSB, CS to GND ................................-0.3V to +6V
SYS to BAT ..............................................................-0.3V to +6V
PG, EP (exposed pad) to GND .............................-0.3V to +0.3V
DC Continuous Current (total in two pins).....................2.4A
USB Continuous Current......................................................1.6A
VL
Single-Layer (derate 20.8mW/°C above +70NC)...1666.7mW
Operating Temperature Range ...........................-40NC to +85NC
Junction Temperature Range ............................-40NC to +150NC
Storage Temperature Range .............................-65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
RMS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
MX8903A-EGHJN/Y
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC INPUT
DC Operating Range
4.15
3.9
16
4.1
4.4
V
V
No valid USB input
Valid USB input
4.0
4.3
When V
goes low, V
DC
DOK
DC Undervoltage Threshold
DC Overvoltage Threshold
rising, 500mV typical hysteresis
4.0
When V goes high, V
hysteresis
rising, 500mV typical
DC
DOK
16.5
17
17.5
4
V
Charger enabled, no switching, V
= 5V
2.3
15
SYS
Charger enabled, f = 3MHz, V
= 5V
DC
DC Supply Current
mA
Charger enabled, V
Charger enabled, V
= 0V, 100mA USB mode (Note 2)
= 5V, 100mA USB mode (Note 2)
1
2
2
CE N
CE N
1
V
= 0V, V
= 5V
USUS
0.10
0.15
0.15
0.31
0.25
DCM
DC High-Side Resistance
DC Low-Side Resistance
DC-to-BAT Dropout Resistance
Ω
Ω
Ω
Assumes a 40mΩ inductor resistance (R )
L
When SYS regulation and charging stops, V
200mV hysteresis
falling,
DC
DC-to-BAT Dropout Voltage
0
15
30
mV
Minimum Off Time (t
Minimum On Time (t
)
100
70
4
ns
ns
OFFMIN
)
ONMIN
V
V
V
V
= 8V, V
= 5V, V
= 9V, V
= 9V, V
= 4V
= 3V
= 4V
= 3V
DC
DC
DC
DC
BAT
BAT
BAT
BAT
MAX8903A/B/C/D/E/H/J/Y
MAX8903G
3
Switching Frequency (f
)
MHz
SW
1
1
DC Step-Down Output Current-
Limit Step Range
0.5
2
A
R
R
R
= 3kΩ
= 6kΩ
= 12kΩ
1900
950
2000
1000
500
2100
1050
550
IDC
IDC
IDC
DC Step-Down Output Current
V
= 6V, V
= 4V
SYS
mA
DC
Limit (I
)
SDLIM
450
2
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
1
MAX
UNITS
ms
No valid USB input
DC Soft-Start Time
Valid USB input before soft-start
20
µs
DC Output Current
500mA USB Mode (Note 3)
V
V
V
= 0V, V
= 0V, V
= 5V
= 0V
= 0V
450
90
475
95
500
100
mA
mA
µA
DCM
DCM
IUSB
IUSB
DC Output Current
100mA USB Mode (Note 2)
SYS to DC Reverse Current
Blocking
= 5.5V, V
0.01
SYS
DC
USB INPUT
USB Operating Range
USB Standoff Voltage
USB Undervoltage Threshold
USB Overvoltage Threshold
4.1
6.3
8
V
V
V
V
When V
When V
goes low, V
rising, 500mV hysteresis
3.95
6.8
90
4.0
6.9
95
4.05
7.0
100
500
3
UOK
UOK
USB
goes high, V
rising, 500mV hysteresis
USB
V
V
= 0V (100mA setting)
= 5V (500mA setting)
IUSB
IUSB
USB Current Limit
mA
450
475
1.3
0.8
0.115
15
I
I
= I
= 0mA, V
= 0mA, V
= 0V
SYS
SYS
BAT
BAT
CEN
CEN
USB Supply Current
mA
= I
= 5V
2
V
= 5V (USB suspend mode)
0.25
30
USUS
Minimum USB to BAT Headroom
USB to SYS Dropout Resistance
0
mV
Ω
0.2
1
0.35
V
V
rising
ms
µs
USB
USB Soft-Start Time
falling below DC UVLO to initiate USB soft-start
20
DC
SYS OUTPUT
MAX8903A/B/E/G/Y
SYSMIN MAX8903C/D/H/J/N
MAX8903A/C/D/H/N/Y
3.0
3.4
Minimum SYS Regulation Voltage
I
V
= 1A,
< V
BAT
SYS
V
V
(V
SYSMIN
)
4.3
4.265
4.4
4.4
4.5
4.395
4.55
Regulation Voltage
I
= 0A
MAX8903B/E/G
MAX8903J
4.325
4.5
SYS
MAX8903A/C/D/H
MAX8903B/E/G/J/N/Y
40
Load Regulation
I
= 0 to 2A
mV/A
SYS
25
CS to SYS Resistance
SYS to CS Leakage
V
V
V
= 6V, V
= 5V, V
= 4V, I = 1A
0.07
0.01
0.05
Ω
µA
Ω
DC
SYS
DC
DCM
SYS
CS
= 5.5V, V
= V = 0V
CS
DC
BAT to SYS Resistance
= V
= 0V, V
= 4.2V, I = 1A
SYS
0.1
100
2.0
USB
BAT
BAT to SYS Reverse Regulation
Voltage
V
= 5V, V
= 0V, V
= 0V, I = 200mA
SYS
50
75
mV
V
USB
DC
IUSB
SYS Undervoltage Threshold
SYS falling, 200mV hysteresis (Note 4)
1.8
1.9
3
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BATTERY CHARGER
T
T
T
T
T
T
T
T
= +25°C
4.179
4.158
4.079
4.059
4.328
4.307
4.129
4.109
-150
4.200
4.200
4.100
4.100
4.350
4.350
4.150
4.150
-100
3.0
4.221
4.242
4.121
4.141
4.372
4.394
4.171
4.192
-60
A
A
A
A
A
A
A
A
MAX8903A/B/C/G/H
MAX8903D/E
MAX8903J
= -40°C to +85°C
= +25°C
= -40°C to +85°C
= +25°C
BAT Regulation Voltage
I
= 0mA
V
BAT
(V
BATREG
)
= -40°C to +85°C
= +25°C
MAX8903Y/N
= -40°C to +85°C
Charger Restart Threshold
BAT Prequal Threshold (V
Prequal Charge Current
Change in V
from DONE to fast-charge
mV
V
BAT
MAX8903A/C/D/H/J/N/Y
MAX8903B/E/G
2.9
3.1
V
rising 180mV
BAT
)
BATPQ
MX8903A-EGHJN/Y
hystersis
2.4
2.5
2.6
Percentage of fast-charge current set at ISET
10
%
R
ISET
R
ISET
R
ISET
= 600Ω
1800
900
2000
1000
500
2200
1100
550
Fast-Charge Current
= 1.2kΩ (MAX8903A/C/D)
= 2.4kΩ
mA
450
DONE Threshold (I
)
Percentage of fast-charge, I decreasing
BAT
10
%
kΩ
TERM
R
ISET
Resistor Range
0.6
2.4
ISET Output Voltage
1.5
1.25
0.05
3
V
ISET Current Monitor Gain
BAT Leakage Current
Charger Soft-Start Time
mA/A
No DC or USB input
4
6
µA
With valid input power, V
= 5V
CEN
1.0
ms
°C
Charger Thermal Limit
Temperature
100
5
Charger Thermal Limit Gain
CHARGER TIMER
Charge current = 0 at +120°C
%/°C
Prequalification Time
Fast-Charge Time
C
C
= 0.15µF
= 0.15µF
33
660
15
min
min
s
CT
CT
MAX8903A/C/D/H/J/N/Y (fixed)
MAX8903B/E/G, C = 0.15µF
Top-Off Timer (t
)
TOP-OFF
132
min
%
CT
Timer Accuracy
-15
40
+15
60
Percentage of fast-charge current below which the timer
clock operates at half-speed
Timer Extend Current Threshold
Timer Suspend Current Threshold
50
20
%
%
Percentage of fast-charge current below which timer
clock pauses
16
24
4
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
THERMISTOR MONITOR
0.27 x
0.28 x 0.29 x
THM Threshold, Hot
When charging is suspended, 1% hysteresis
When charging is suspended, 1% hysteresis
THM function is disabled below this voltage
MAX8903B/MAX8903E/MAX8903G
V
V
V
V
V
V
V
VL
VL
VL
0.73 x
0.74 x 0.75 x
THM Threshold, Cold
V
V
V
VL
VL
VL
0.0254 0.03 x 0.036 x
x V
THM Threshold, Disabled
THM Threshold DC, USB Enable
V
V
VL
VL
VL
0.83 x
0.87 x 0.91 x
V
V
V
VL
VL
VL
THM = GND or VL;
-0.100
0.001 +0.200
0.010
T
A
= +25°C
MAX8903A/C/D/H/J/N/Y
MAX8903B/E/G
THM = GND or VL;
THM Input Leakage
µA
T
= +85°C
A
THM = GND or VL;
= -40°C to +85°C
-0.200
0.001 +0.200
T
A
THERMAL SHUTDOWN, VL, AND LOGIC I/O: CHG, FLT, DOK, UOK, DCM, CEN, USUS, IUSB
High level
1.3
V
Logic-Input Thresholds
(DCM, CEN, USUS, IUSB)
Low level
0.4
Hysteresis
50
mV
T
T
= +25°C
= +85°C
-1.000
-0.200
0.001 +1.000
0.010
A
V
= 0V to 5.5V
INPUT
(MAX8903A/C/D/H/J/N/Y)
Logic-Input Leakage Current
(CEN, USUS, IUSB)
A
µA
V
= 0V to 5.5V
INPUT
T
A
= -40°C to +85°C
0.001 +0.200
(MAX8903B/E/G)
T
T
= +25°C
= +85°C
0.001
0.01
8
1
50
1
A
Logic-Input Leakage Current
(DCM)
V
V
= 0V to 16V
DCM
µA
mV
µA
= 16V
DC
A
Sinking 1mA
Sinking 10mA
Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)
80
T
T
= +25°C
= +85°C
0.001
0.01
A
Open-Drain Output Leakage
Current, High (CHG, FLT, DOK, UOK)
V
= 5.5V
OUT
A
5
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40NC to +85NC, unless otherwise noted. Typical values are at T = +25NC.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
= 0 to 1mA
MIN
TYP
MAX
UNITS
I
VL
4.6
5.0
5.4
(MAX8903A/C/D/H/J/N/Y)
VL Output Voltage
V
V
= V
= 6V
USB
V
DC
VL
I
VL
= 0 to 10mA
4.6
5.0
5.4
(MAX8903B/E/G)
VL UVLO Threshold
falling; 200mV hysteresis
3.2
160
15
V
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
°C
°C
Note 1: Limits are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.
A
Note 2: For the 100mA USB mode using the DC input, the step-down regulator is turned off and its high-side switch operates as a
linear regulator with a 100mA current limit. The linear regulator’s output is connected to LX and its output current flows
through the inductor into CS and finally to SYS.
Note 3: For the 500mA USB mode, the actual current drawn from USB is less than the output current due to the input/output current
ratio of the DC-DC converter.
MX8903A-EGHJN/Y
Note 4: For short-circuit protection, SYS sources 25mA below V
= 400mV, and 50mA for V
between 400mV and 2V.
SYS
SYS
典型工作特性
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/D/E/H/J/N/Y
BATTERY CHARGER EFFICIENCY
vs. BATTERY VOLTAGE
MAX8903A/B/C/D/E/H/J/N/Y
SWITCHING FREQUENCY vs. V
MAX8903G BATTERY CHARGER
EFFICIENCY vs. BATTERY VOLTAGE
DC
100
90
100
90
80
70
60
50
40
30
20
10
0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
V
= 6V
80
DC
V
= 5V
DC
70
60
50
40
30
20
10
0
V
= 9V
V
= 3V
= 4V
DC
BAT
V
DC
= 8V
V
BAT
V
DC
= 12V
V
= 12V
I
DC
I
= 0.15A
= 1.5A
I
= 0.15A
I
= 1.5A
BAT
BATT
BATT
BAT
R
V
= 1.2kΩ
= 0V
ISET
CEN
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
4
6
8
10
12
14
16
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
DC VOLTAGE (V)
6
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
典型工作特性(续)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/D/E/H/J/N/Y
SYS EFFICIENCY
MAX8903G SYS EFFICIENCY
vs. SYS OUTPUT CURRENT
MAX8903G SWITCHING
vs. SYS OUTPUT CURRENT
FREQUENCY vs. V
DC
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
V
= 1V
= 4.4V
CEN
SYS
V
CEN
= 1
V
= 16V
DC
V
= 11V
DC
V
= 12V
V
= 4V
DC
BAT
V
= 16V
DC
V
= 9V
V
= 3V
DC
BAT
V
= 6V
DC
V
= 6V
DC
R
V
= 1.2kI
= 0V
ISET
CEN
V
= 4.5V
1000
DC
1
10
100
10000
1
10
100
1000
10,000
4
6
8
10
12
14
16
SYS OUTPUT CURRENT (mA)
SYS OUTPUT CURRENT (mA)
DC VOLTAGE (V)
USB SUPPLY CURRENT
vs. USB VOLTAGE
BATTERY LEAKAGE CURRENT
vs. BATTERY VOLTAGE
USB SUPPLY CURRENT
vs. USB VOLTAGE (SUSPEND)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
80
70
60
50
40
30
20
10
0
140
120
100
80
CHARGER
ENABLED
60
40
CHARGER
DISABLED
20
NO DC OR USB INPUT
USB SUSPEND
0
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
USB VOLTAGE (V)
BATTERY VOLTAGE (V)
USB VOLTAGE (V)
CHARGE CURRENT
vs. BATTERY VOLTAGE—USB MODE
BATTERY LEAKAGE CURRENT
vs. AMBIENT TEMPERATURE
CHARGE CURRENT
vs. BATTERY VOLTAGE—DC MODE
500
450
400
350
300
250
200
150
100
50
90
80
70
60
50
40
30
20
10
0
1200
1000
800
600
400
200
0
CHARGER ENABLED
CHARGE ENABLED
I
I
SET TO 1A
SET TO 2A
I
SET TO 1.5A
BAT
BAT
MAX8903D
DC
MAX8903A/C/H
RISING
V
BAT
RISING
V
BAT
V
= V
USB
IUSB
V
IUSB
= 0V
NO DC OR USB INPUT
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1.5
2.0
2.5
3.0
3.5
4.0
4.5
-40
-15
10
35
60
85
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
TEMPERATURE (°C)
7
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
典型工作特性(续)
(T = +25°C, unless otherwise noted.)
A
NORMALIZED BATTERY
REGULATION VOLTAGE
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. USB VOLTAGE
NORMALIZED CHARGE CURRENT
vs. AMBIENT TEMPERATURE
1.015
vs. AMBIENT TEMPERATURE
100.5
100.4
100.3
100.2
100.1
100.0
99.9
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
V
V
= 5V
= 0V
= 0V
V
USB
= 5V, V = 4V
BAT
CEN
BAT
DC
1.010
1.005
1.000
0.995
0.990
0.985
V
FALLING
USB
V
RISING
USB
99.8
99.7
99.6
R
= 1MΩ
SYS
22ppm/°C
60 85
99.5
0
1
2
3
4
5
6
7
-40
-15
10
35
-40
-15
10
35
60
85
MX8903A-EGHJN/Y
USB VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, DC INPUT
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. DC VOLTAGE
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, USB INPUT
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
V
= 0V
MAX8903J, V = 5.75V
USB
DC
V
= 0V, V
= 4V
DC
BATT
MAX8903J, V
= 5V
USB
V
RISING
DC
MAX8903A/C/D/H, MAX8903N/Y,
MAX8903A/C/D/H, MAX8903N/Y,
= 5V = 5V
V
DC
= 5.75V
V
= 5.75V
DC
V
V
USB
USB
MAX8903B/E/G,
= 5.75V
MAX8903B/E/G,
= 5V
V
FALLING
DC
V
DC
V
USB
V
CEN
V
BAT
V
USB
= 5V
= 0V
= 0V
MAX8903_, V = 0V
MAX8903_, V
= 0V
DC
USB
0
0.5
1.0
1.5
2.0
0
2
4
6
8
10 12 14 16 18
0
100
200
300
400
500
SYS OUTPUT CURRENT (A)
DC VOLTAGE (V)
SYS OUTPUT CURRENT (mA)
CHARGE PROFILE—1400mAh BATTERY
VL VOLTAGE vs. DC VOLTAGE
ADAPTER INPUT—1A CHARGE
MAX8903A toc17
6
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
I
SET TO 1A
SET TO 2A
DC
I
BAT
5
4
3
2
1
0
V
BAT
VL WITH
NO LOAD AND
DCDC OFF
VL AND DCDC
WITH
FULL LOAD
(V
= 5V)
(V
= 0V)
USUS
USUS
I
BAT
V
BAT
= 3.6V
V
= 0V
USB
MAX8903A/B/C/G/H
0
2
4
6
8
10 12 14 16 18 20
0
20
40
60
80
100 120 140
DC VOLTAGE (V)
TIME (min)
8
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
典型工作特性(续)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/G/H
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
CHARGE PROFILE—1400mAh BATTERY
WAVEFORMS—LIGHT LOAD
USB INPUT—500mA CHARGE
MAX8903A toc19
MAX8903A toc18
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
20mV/div
AC-COUPLED
V
OUT
V
BAT
5V/div
0V
V
LX
LX
I
BAT
I
MAX8903A/MAX8903B/MAX8903C
SET TO 500mA
500mA/div
0A
I
USB
R
= 44Ω
SYS
I
SET TO 2A
BAT
200ns/div
0
20 40 60 80 100 120 140 160 180 200
TIME (min)
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
WAVEFORMS—LIGHT LOAD
MAX8903A toc20
MAX8903A toc19a
20mV/div
50mV/div
AC-COUPLED
AC-COUPLED
V
OUT
V
SYS
V
= 9V, L = 2.2µH
DC
C
R
= 22µF,
= 44I
SYS
SYS
5V/div
0V
V
I
V
10V/div
LX
LX
0V
1A/div
LX
I
LX
0A
500mA/div
0A
R
= 5Ω
SYS
200ns/div
1µs/div
DC CONNECT WITH
USB CONNECTED (R = 25Ω)
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
SYS
MAX8903A toc21
MAX8903A toc20a
3.6V
2V/div
V
50mV/div
SYS
V
SYS
AC-COUPLED
V
= 9V, L = 2.2µH
I
DC
DC
500mA/div
347mA
C
= 22µF, R = 5I
SYS
SYS
CEN = 1
10V/div
0V
475mA
500mA/div
V
I
LX
I
USB
-I = CHARGING
BAT
0A
I
-335mA
BAT
500mA/div
LX
1A/div
0A
200µs/div
1µs/div
9
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
典型工作特性(续)
(T = +25°C, unless otherwise noted.)
A
DC CONNECT WITH NO USB
DC DISCONNECT WITH NO USB
(R = 25Ω)
(R
= 25Ω)
SYS
SYS
MAX8903A toc22
MAX8903A toc23
3.84V
3.68V
3.6V
3.6V
3.6V
3.6V
2V/div
5V/div
2V/div
5V/div
V
V
SYS
SYS
3.44V
V
V
BAT
BAT
C
DC
C
SYS
CHARGING
CHARGING
850mA
1A/div
1A/div
1A/div
1A/div
I
0A
0A
DC
850mA
-1A
I
DC
-I = CHARGING
BAT
I
BAT
I
144mA
BAT
144mA
-I = CHARGING
BATTERY
CHARGER
SOFT-START
-1A
BAT
400µs/div
40µs/div
MX8903A-EGHJN/Y
MAX8903A/C/D/H SYS LOAD TRANSIENT
MAX8903B/E SYS LOAD TRANSIENT
MAX8903A toc24a
MAX8903A toc24b
MAX8903B
V
= 10.5V
DC
L = 2.2µH
4.400V
C
= 22µF
SYS
MAX8903A
V
4.325V
R
= 3kI (2A)
SYS
IDC
20mV/div
AC-COUPLED
V
= 10.5V
DCM = HIGH
CEN = 1
DC
V
I
SYS
4.360V
1A
20mV/div
L = 2.2µH
4.305V
C
= 10µF
SYS
R
IDC
= 3kI (2A)
1A
DCM = HIGH
CEN = 1
I
SYS
SYS
500mA/div
0A
0A
500mA/div
0A
0A
100µs/div
100µs/div
USB CONNECT WITH NO DC
(R
= 25Ω)
MAX8903G SYS LOAD TRANSIENT
SYS
MAX8903A toc25
MAX8903A toc24c
3.6V
3.75V
2V/div
5V/div
4.325V
= 9V
V
SYS
3.5V
USB
5V
4.305V
50mV/div
V
SYS
V
USB
V
DC
C
L = 2.2µH
CHARGING
475mA
C
= 22µF
SYS
500mA/div
500mA/div
R
= 3kI (2A)
IDC
1A
I
USB
DCM = 1
CEN = 1
I
SYS
I
BAT
144mA
BATTERY
CHARGER
SOFT-START
500mA/div
0A
0A
-330mA
400µs/div
100µs/div
10
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
典型工作特性(续)
(T = +25°C, unless otherwise noted.)
A
USB DISCONNECT WITH NO DC
(R
= 25Ω)
USB SUSPEND
USB RESUME
SYS
MAX8903A toc26
MAX8903A toc27
MAX8903A toc28
0V
0V
3.6V
3V
3V
V
V
2V/div
5V/div
5V/div
5V/div
USUS
USUS
V
SYS
C
USB
CHARGING
500mA/div
500mA/div
V
USB
475mA
475mA
3.6V
5V
I
0A
0A
USB
I
USB
475mA
3.8V
3.6V
V
V
SYS
SYS
500mA/div
500mA/div
2V/div
2V/div
3.7V
I
USB
I
I
BAT
BAT
-330mA
144mA
I
BAT
0A
-475mA
-475mA
0A
BATTERY
CHARGER
500mA/div
500mA/div
SOFT-START
100µs/div
200µs/div
200µs/div
引脚说明
引脚
名称
功能
1, 2
PG
降压低边同步n沟道MOSFET的功率地，两个PG引脚必须在外部连接在一起。
直流电源输入。DC能够向SYS提供高达2A的电流。DC支持交流适配器和USB输入，DC限流根据所使用的输入
电源通过DCM、IUSB或IDC设置，请参考表2。两个DC引脚必须在外部连接在一起。请在DC和PG之间连接一
个至少4.7μF的陶瓷电容。
3, 4
DC
直流电源输入的限流模式设置。置于逻辑高电平时，直流输入电流门限由IDC与GND之间的电阻设置；置于逻
辑低电平时，直流输入电流门限在内部设置为500mA或100mA，由IUSB的逻辑输入设置。DCM (阳极)与DC
(阴极)之间接有一个内部二极管，如图1所示。
5
DCM
6
7
BST
高边MOSFET驱动电源。用一个0.1μF陶瓷电容将BST旁路至LX。
USB限流设置输入。将IUSB驱动至逻辑低电平时，USB电流门限为100mA；将IUSB驱动至逻辑高电平
时，USB电流门限为500mA。
IUSB
直流电源就绪输出。当在DC上检测到有效输入时，将低电平有效的开漏输出拉至低电平。当充电器被禁用
(CEN为逻辑高电平)时，DOK仍然保持有效输出。
8
DOK
逻辑电路LDO输出。VL为LDO输出，该输出向MAX8903_内部电路供电并向BST电容充电。在VL和GND之间连
接一个1μF的陶瓷电容。
9
VL
CT
10
11
12
充电定时器设置输入。CT和GND之间的电容(CCT)用于设置快充和预充故障定时器，该引脚接GND时禁用定时器。
直流电源限流设置输入。在IDC和GND之间连接一个电阻(RIDC)，当DCM为逻辑高电平时，降压调节器的电流
门限设置为0.5A至2A。
IDC
GND
地，GND是内部电路的低噪声接地端。
11
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
引脚说明(续)
引脚
名称
功能
13
ISET
充电电流设置输入。ISET和GND之间的电阻(RISET)用于设置快充电流，最大值为2A。预充电流为快充电流的10%。
充电器使能输入。CEN接GND时，如果DC或USB连接到有效电源则使能电池充电；接VL时，或将其驱动至逻
辑高电平，则禁止电池充电。
14
15
CEN
USB挂起输入。USUS驱动至逻辑高电平时进入USB挂起模式，USB电流降低至115μA，并在内部将SYS短路
至BAT。
USUS
热敏电阻输入。将一个负温度系数(NTC)热敏电阻连接在THM和GND之间。将一个阻值等于+25°C时热敏电阻
阻值的电阻连接在THM和VL之间。当热敏电阻超出高温、低温门限时，充电器被挂起。将THM连接至GND
时，禁用热敏电阻温度检测。
16
THM
USB电源输入。USB能够向SYS提供100mA或500mA电流，取决于IUSB逻辑输入的设置。在USB和GND之间
连接一个4.7μF的陶瓷电容。
17
18
19
USB
FLT
故障指示输出。若电池定时器在快充或预充完成之前超时，低电平有效的开漏输出将被拉至低电平。
USB电源就绪输出。当在USB上检测到有效输入时，低电平有效的开漏输出被拉至低电平。充电器禁用(CEN
为逻辑高)时，UOK仍然保持有效。
UOK
电池连接端，连接到单节Li+电池。当DC或USB存在有效电源时，电池通过SYS充电。当DC和USB均不存在有效
电源时，或当SYS负载超过输入电流门限时，BAT向SYS供电。两个BAT引脚必须在外部连接到一起。
20, 21
22
BAT
MX8903A-EGHJN/Y
CHG
充电器状态输出。当电池处于快充或预充电状态时，低电平有效的开漏输出被拉至低电平；否则，CHG为高阻态。
系统电源输出。当DC或USB无效，或者SYS负载超过输入电流门限时，SYS通过内部50mΩ系统负载开关连接
至BAT。
当DC或USB连接有效电源时，SYS电压限制在VSYSREG。系统负载(ISYS)超过DC或USB电流门限时，SYS被调
节到低于BAT 50mV，输入电源和电池都向SYS供电。
23, 24
SYS
利用X5R或X7R陶瓷电容将SYS旁路至GND，SYS电容(CSYS)的最小推荐值参见表6。两个SYS引脚必须在外部
连接到一起。
70mΩ电流检测输入。降压电感连接在LX和CS之间。当降压调节器开启时，CS和SYS之间有一个70mΩ电流
检测MOSFET；当降压调节器关闭时，内部CS MOSFET断开，防止电流从SYS倒灌至DC。
25, 26
CS
27, 28
—
LX
EP
电感连接端，将电感连接在LX和CS之间。两个LX引脚必须从外部连接在一起。
裸焊盘，将裸焊盘连接至GND。裸焊盘连接并不能替代相应引脚的接地要求。
12
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
PG
LX
BST
CS
MAX8903_
DC POWER
MANAGEMENT
TO
SYSTEM
LOAD
DC
SYS
AC
ADAPTER
PWR
OK
Li+ BATTERY
CHARGER
AND SYS LOAD SWITCH
ISET
PWM
STEP-DOWN
REGULATOR
DOK
CHARGER
BATTERY
CONNECTOR
CURRENT-
VOLTAGE
CONTROL
SET
BAT
INPUT
LIMIT
BAT+
BAT-
+
USB POWER
MANAGEMENT
USB
UOK
T
USB
THERMISTOR
MONITOR
(SEE FIGURE 7)
THM
VL
NTC
PWR
OK
CURRENT-
LIMITED
VOLTAGE
IC
THERMAL
REGULATION
REGULATOR
CHG
CHARGE
TERMINATION
AND MONITOR
SET
INPUT
LIMIT
DC
DCM
IUSB
FLT
CT
DC MODE
500mA
CHARGE
TIMER
INPUT AND
USB
CHARGER
CURRENT-LIMIT
SET LOGIC
LIMIT
100mA
USUS
IDC
USB
SUSPEND
CEN
GND
DC
EP
LIMIT
图1. 功能框图
13
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
R
PU
4 x 100kΩ
TO VL
1
PG
2
PG
18
19
8
FAULT
FLT
UOK
DOK
CHG
MAX8903_
OUTPUT
C
DC
4.7µF
USB PWR OK
DC PWR OK
3
DC
DC
ADAPTER
4
6
22
CHARGE
INDICATOR
BST
C
0.1µF
BST
R
R
ISET
27 LX
LX
13
11
ISET
IDC
28
IDC
L1
1µH
25 CS
26 CS
(SEE TABLE 5 FOR
INDUCTOR SELECTION)
SYS 24
TO SYSTEM
LOAD
MX8903A-EGHJN/Y
C
SYS
23
SYS
(SEE TABLE 6 FOR C SELECTION)
SYS
USB
BAT
BAT
21
20
17 USB
VBUS
C
4.7µF
C
10µF
USB
BAT
1-CELL
LI+
GND
5
TO DC
DCM
9
VL
14
OFF
CHARGE ON
C
1µF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15µF
图2．典型应用电路，使用独立的DC和USB连接器
USB充电输入可以通过USB电源向电池充电并向系统供电。
当由USB或DC输入供电时，如果系统负载电流峰值超出了
输入电源的供电能力，不足部分可由电池补充。
电路说明
MAX8903_为双输入充电器，输入为16V宽范围直流电源和
USB电源。IC内部包括一路高压(16V)输入DC-DC降压转
换器，在保证系统负载供电的同时有效降低充电器功耗。
降压转换器可向系统、电池或两者组合提供高达2A的电流。
MAX8903_还利用一个片上50mΩ MOSFET管理负载与电
池和外部电源之间的切换。该开关在输入电源过载时，能
够通过电池支持负载的峰值电流。
14
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
R
PU
4 x 100kΩ
TO VL
1
2
PG
PG
18
19
8
FAULT
FLT
UOK
DOK
CHG
MAX8903_
OUTPUT
C
DC
4.7µF
USB PWR-OK
DC PWR-OK
3
DC
DC
VBUS
4
6
D-
22
CHARGE
INDICATOR
BST
D+
C
0.1µF
BST
R
R
ISET
27 LX
LX
13
11
ID
ISET
IDC
GND
28
IDC
L1
1µH
25 CS
26 CS
SYS 24
TO SYSTEM
LOAD
(SEE TABLE 6 FOR C SELECTION)
499kΩ
C
SYS
23
SYS
(SEE TABLE 5 FOR
INDUCTOR VALUE
SELECTION)
SYS
BAT
BAT
21
20
17 USB
C
BAT
1-CELL
LI+
USB
ADAPTER
DC MODE
10µF
5
DCM
9
VL
14
OFF
CHARGE ON
C
1µF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15µF
图3．典型应用电路，使用Mini 5型连接器或其它DC/USB普通连接器
如图1所示，该IC包括完备的充电器功能，具有热敏电阻
监测器、故障定时器、充电状态指示和故障指示输出。还
包括USB和DC电源就绪指示，可灵活调节充电电流、输入
电流门限和最小系统电压(按比例降低充电电流，以保持系
统电压正常)。
DC输入—高速滞回降压调节器
如果存在有效的DC输入，则关闭USB电源通路，由高频
降压调节器将DC输入转换成SYS和电池充电的供电电源。
如果电池电压高于最小系统供电电压(VSYSMIN，图4)，电
池充电器将系统供电电压连接至电池，以获得最低功耗。
利用三个反馈信号控制降压调节点：IDC设置的最大降压
输出电流、ISET设置的最大充电电流以及最高管芯温度。
反馈信号只需最小的电流控制电感的平均输出电流。这种
机制使电池充电的总功耗最小，电池能够在保持最小系统
电压波动的前提下化解负载瞬变的影响。
+
°
当管芯温度超过 100 C时，MAX8903_会限制充电电流，
从而防止高温环境下出现过热。
15
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
表1．图2和图3的外部元件列表
COMPONENT
FUNCTION
PART
(FIGURES 2 AND 3)
C
, C
Input filter capacitor
VL filter capacitor
4.7µF ceramic capacitor
1.0µF ceramic capacitor
DC USB
C
VL
10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J) or
22µF (MAX8903B/MAX8903E/MAX8903G/MAX8903Y) ceramic capacitor
C
SYS output bypass capacitor
SYS
C
Battery bypass capacitor
Charger timing capacitor
Logic output pullup resistors
Negative TC thermistor
THM pullup resistor
10µF ceramic capacitor
BAT
C
0.15µF low TC ceramic capacitor
CT
R
(X4)
100kΩ
PU
THM
Philips NTC thermistor, P/N 2322-640-63103, 0kΩ 5ꢀ at ꢁ25ꢂC
10kΩ
R
T
R
DC input current-limit programming resistor 3kΩ 1ꢀ, for 2A limit
IDC
ISET
L1
R
Fast-charge current programming resistor 1.2kΩ 1ꢀ, for 1A charging
DC input step-down inductor
1µH inductor with I
> 2A
SAT
MX8903A-EGHJN/Y
如果电池电压低于VSYSMIN，充电器不直接将系统供电电压
连接至电池，系统电压(VSYS)略高于VSYSMIN，如图4所示。
电池充电器独立控制电池的充电电流。根据MAX8903_版
本的不同，VSYSMIN设置为3.0V或3.4V，参见表6。
DC模式(DCM)
如表2所示，DC输入可接受交流适配器(最高2A)和USB (最
高500mA)电源。DCM逻辑输入置为高电平时，DC输入处
于适配器模式，DC输入电流限制由IDC与GND之间的电阻
(RIDC)设置。根据下式计算RIDC
:
电池充电至VSYSMIN电压以上50mV后，系统供电电压被连
接至电池。随后，电池快充电流控制降压转换器建立平均
电感电流，以满足输入限流和快充电流限制的要求。
RIDC = 6000V/IDC-MAX
DCM逻辑输入置为低电平时，DC输入电流限制由IUSB逻
辑输入在内部设置为500mA或100mA。IUSB逻辑输入为
高电平时，DC输入电流限制为500mA，DC输入通过降压
调节器为SYS供电。IUSB逻辑输入为低电平时，DC输入
电流限制为100mA。在100mA模式下，降压调节器关闭，
高边开关将构成线性稳压器，具有100mA的限流。线性稳
压器的输出连接至LX，输出电流经电感流入CS，最终流
入SYS。
DC-DC降压控制机制
专有的滞回电流PWM控制机制可确保工作在较高的开关
频率，允许使用小尺寸外部元件。反馈控制信号需要最小
的输入电流，控制电感的峰值和谷值电流的中点。纹波电
流由内部设置，使转换器工作在4MHz频率。当输入电压
降至输出电压附近时，工作在非常高的占空比，由于存在
最小关断时间，达不到4MHz工作频率。控制器提供最小
关断时间、峰值电流调节。类似地，当输入电压较高时，
由于存在最小导通时间，不能工作在4MHz频率，此时控
制器采用最小导通时间、谷电流控制。这种情况下，电感
的纹波电流始终保持最小，能够在给定电容下有效降低
SYS的纹波电压。为了避免工作频率波动，纹波电流随输
入电压、输出电压而变化。然而，频率也会随着工作条件
的不同而发生变化，请参考典型工作特性部分。
DCM引脚具有一个内部连接至DC的二极管，如图1所示。
为防止电流从DCM经内部二极管流至DC输入，DCM的
驱动电压不能大于DC。图3所示电路中，通过一个简单的
MOSFET和DCM端的外部电阻即可防止电流从DCM经内
部二极管流至DC。图3中的电路允许微处理器在任何时候
将MOSFET的栅极驱动至任何状态。
16
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
图3中MOSFET和DCM端电阻的一种替代方案是在DCM输
入与微处理器之间串联一个1MΩ电阻。微处理器监测DOK
输出，确保在DOK为高电平时DCM仍然为低电平。如果
DCM的驱动电压高于DC，1MΩ串联电阻把从DCM经内部
UOK和DOK电路在热过载、USB挂起以及充电器被禁止时
均保持有效工作状态。也可以将DOK和UOK“线或”连接，
构成一路电源就绪(POK)输出。
热保护
μ
二极管流至DC的电流限制在几个 A。
+
°
°
当管芯温度超过 100 C时，热保护电路将按照5%/ C降低
USB输入—线性稳压器
°
输入电流门限，温度达到+120 C时充电电流为0mA。由于
如果USB输入有效、DC输入无效，SYS和电池充电电流均
由连接在USB和SYS之间的低压差线性稳压器提供。SYS
的稳压特性与DC输入条件下相同(图4所示)。电池充电器
将从SYS获取所能提供的电流，但不会超出最大允许的
USB电流。如果USB和DC输入均有效，则由DC输入供电。
最大USB输入电流由IUSB输入的逻辑状态设置为100mA
或500mA。
系统负载供电的优先级高于电池充电，电池充电电流会在
输入限制器拉低SYS负载电压之前降至0mA。为避免错误
地结束充电，该模式下的充电终止检测功能被禁用。如果
结温上升至 120 C以上，不会从DC或USB吸收电流，并
且VSYS调节到低于VBAT 50mV。
+
°
系统电压切换
DC输入
当由DC输入充电时，如果电池电压高于最小系统电压，SYS
则被连接至电池。电流供给SYS和电池，可以达到最大设
置值。降压转换器输出电流检测和充电电流检测所提供的
反馈确保电流环路需要较低的输入电流。当从DC供电时，
这种方法的优势在于功耗主要取决于降压调节器的效率，
因为SYS和BAT之间的压降非常低。此外，电池能够吸收
负载瞬变的影响，使SYS电压波动最小。若DC和USB输入
均有效，则DC输入优先级较高，由它提供输入电流，同
时USB输入被关闭。
电源监测器输出(UOK、DOK)
DOK为漏极开路、低电平有效输出，指示DC输入电源的
状态。若USB引脚没有电源，当4.15V< VDC < 16V时，DC
电源被认为有效且DOK驱动至逻辑低电平；若USB电源
也有效，当4.45V < VDC < 16V时，DC电源被认为有效且
DOK驱动至逻辑低电平。USB输入有效时，如果最小DC
电压值较高，则有利于输入电源之间的低噪声转换。如果
不需要DC电源就绪输出，可将DOK连接至地。
UOK为漏极开路、低电平有效输出，指示USB输入电源的
状态。USB连接有效电源时，UOK为逻辑低电平；4.1V <
VUSB < 6.6V时，USB电源有效。如果不需要USB电源就绪
输出，可将UOK连接至地。
电池完成充电后，充电器关闭，SYS负载电流由DC输入提
供，SYS电压稳定在VSYSREG。电池电量下降到重新启动
充电的门限时，再次打开充电器。如果负载电流超出输
入门限，SYS电压降至电池电压，并且SYS和BAT之间的
50mΩ PMOS开关导通，以支持更大的负载电流。一旦负
载电流低于输入电流门限，SYS和BAT之间的开关被关闭。
如果撤除有效的DC电源，则50mΩ PMOS也将导通。
V
V
SYSREG
BATREG
MAX8903_
USB输入
由USB输入充电时，DC输入降压调节器关闭，连接在USB
和SYS之间的线性稳压器向系统供电并向电池充电。如果
电池电压高于最小系统电压，SYS供电电压被连接至电池。
USB输入向SYS负载供电，并利用额外的电流为电池充电，
总电流不会超过最大允许的USB电流。电池能够吸收负载
瞬变的影响，使SYS电压波动最小。电池充电结束或充电
器被禁止时，SYS电压稳定在VSYSREG。如果USB和DC输
入均有效，则只从DC输入供电。
V
SYS
I
x R
ON
BAT
V
SYSMIN
V
V
= 0V
AND/OR V
CEN
= 5.0V
USB
DC
V
BAT
图4．SYS跟随VBAT至最小系统电压
17
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
表2．输入限制器控制逻辑
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
MAXIMUM
CHARGE
CURRENT**
USB INPUT
CURRENT LIMIT
POWER SOURCE
DOK
UOK DCM*** IUSB USUS
Lesser of
1200V/R
6000V/R
and
AC Adapter at DC Input
L
L
X
X
H
L
X
L
X
L
6000V/R
IDC
ISET
IDC
Lesser of
1200V/R
100mA
and
USB input off. DC
input has priority.
ISET
100mA
USB Power at DC Input
Lesser of
1200V/R
and
L
L
X
X
L
L
L
X
H
X
L
L
H
L
500mA
ISET
500mA
USB suspend
0
Lesser of
1200V/R
MX8903A-EGHJN/Y
H
100mA
500mA
and
ISET
100mA
USB Power at USB Input,
DC Unconnected
Lesser of
1200V/R
ISET
No DC input
H
L
X
H
L
and
500mA
H
H
L
X
X
X
X
H
X
USB suspend
No USB input
0
0
DC and USB Unconnected
H
**充电电流不能超过输入电流门限，如果总的SYS负载电流超过输入限流，将控制充电电流低于最大充电电流。
***DCM (阳极)与DC (阴极)之间接有一个内部二极管，如图1所示。如需通过μP设置DCM电平，需采用一个MOSFET进行隔离，如图3
所示。X = 无关。
USB挂起
软启动
为了防止能够导致USB或交流适配器电源不稳定的输入瞬
变，输入电流和充电电流的变化率均受限。当一路输入电
源有效时，SYS电流从零开始上升到所设置的电流门限，
驱动USUS为逻辑高电平、DCM为逻辑低电平将关闭充电
器和SYS输出，并将输入电流降至170 A，进入USB挂起
μ
模式。请参考表2所示的设置。
μ
通常时间为50 s。这也意味着，如果DC在USB之后有效，
充电使能(CEN)
CEN为逻辑低电平时，充电器开启；CEN为逻辑高电平
时，充电器关闭。CEN不影响SYS输出。许多系统中，不
需要系统控制器(通常为微处理器)关闭充电器工作，因为
MAX8903_智能电源选择器能够独立地管理充电和适配器/
电池电源的关断。这种情况下，CEN可以接地。
SYS电流将在USB切换到DC输入之前降至零。在某个工作
点，SYS可能无法支持负载供电，切换至BAT。当VSYS
VBAT时，将切换至BAT。该门限具体取决于SYS电容和
SYS负载。SYS电流随后从零上升到所设置的电流，只要
SYS负载电流小于所设置的电流门限，SYS即可支持负载。
<
18
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
充电器开启时，充电电流从0A上升到ISET设置的电流，通
常时间为1.0ms。当从预充进入快充状态、输入电源在USB
和DC之间切换、IUSB逻辑输入将USB充电电流从100mA
变为500mA时，充电电流也会进入软启动过程。然而，如
果RISET通过一个开关突然改变，则没有di/dt限制。
当VBAT低于VBATPQ时，充电器进入预充模式，以最大快
充速率的10%为电池充电，直到过放电电池恢复正常。当
电池电压达到VBATREG时，充电电流下降到最大快充电流
的10%，充电器进入DONE状态。当电池电压跌落100mV
时，充电器将重新启动快充过程。
电池充电器
存在有效的输入电源时，电池充电器将尝试以快充电流为
电池充电，电流由ISET与GND之间的电阻确定，根据下式
计算RISET电阻：
充电终止
当充电电流降至终止门限(ITERM)并且充电器处于恒压模式
时，完成充电。充电过程将持续短暂的15s浮充周期，然
后进入DONE状态，充电结束。
R
ISET = 1200V/ICHGMAX
注意，若充电电流因为输入限流或热保护下降至ITERM，充
电器不会进入DONE状态。若要充电器进入DONE状态，充
电电流必须低于ITERM并且充电器必须处于恒压模式、输入
限流或热保护电路没有降低充电电流。
监测充电电流
ISET和GND之间的电压代表电池充电电流，可用于监测电
池的充电电流。1.5V电压对应于最大快充电流。
充电状态指示输出
必要时，充电器可自动降低充电电流，以防SYS电压跌落。
因此，USB供电时充电器不会以超出100mA或500mA电流
向电池充电，也不会造成交流适配器过载，请参考图5。
充电指示输出(CHG)
CHG为漏极开路、低电平有效输出，用于指示充电器状态。
当电池充电器处于预充和快充状态时，CHG为低电平。如
果热敏电阻检测使充电器进入热保护状态，CHG将变为高
阻态。
MONITORING THE BATTERY
μ
与微处理器( P)配合使用时，在CHG和逻辑I/O电压之间连
CHARGE CURRENT WITH V
ISET
μ
接一个上拉电阻，为 P提供充电状态指示。此外，CHG可
吸收最大20mA的电流，能够用于LED充电指示。
1.5
ISET
0
故障指示输出(FLT)
FLT为漏极开路、低电平有效输出，用于指示充电器状态。
电池充电器进入故障状态并且充电定时器超时的情况下，
FLT为低电平。当充电器处于预充状态的时间超过33分钟
或充电器处于快充状态的时间超过660分钟时，可能发生
这种情况(图6所示)。为了退出故障状态，可以触发CEN或
重新接通输入电源。
V
(V)
μ
与微处理器( P)配合使用时，在FLT和逻辑I/O电压之间连
μ
接一个上拉电阻，为 P提供充电状态指示。此外，FLT可吸
收最大20mA的电流，能够用于LED充电指示。如果不需要
FLT输出，可将FLT接地或浮空。
0
BATTERY CHARGING CURRENT (A)
DISCHARGING
1200V/R
ISET
充电定时器
故障定时器可避免电池无限制地充电。预充和快充故障定
时器由CT端的外接电容(CCT)设置。
图5．利用ISET和GND之间的电压监测电池充电电流
19
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
CEN = HI OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
NOT READY
UOK AND DOK = HIGH IMPEDANCE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ANY STATE
I
= 0mA
CHG
UOK AND/OR DOK = LOW
CEN = 0
RESET TIMER
TOGGLE CEN OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
PREQUALIFICATION
UOK AND/OR DOK = LOW
CHG = LOW
TIMER > t
PREQUAL
FLT = HIGH IMPEDANCE
FAULT
0 < V < V
BAT
BATPQ
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = LOW
I
≤ I
/10
CHG CHGMAX
V
BAT
< V
BATPQ
- 180mV
V
> V
BAT BATPQ
I
= 0mA
CHG
RESET TIMER = 0
RESET TIMER
TIMER > t
FSTCHG
(TIMER SLOWED BY 2x IF
< I /2, AND
FAST-CHARGE
UOK AND/OR DOK = LOW
CHG = LOW
I
CHG CHGMAX
V
< V
- 180mV
RESET TIMER
BAT
BATPQ
PAUSED IF I
< I
/5 WHILE V < V
)
BATREG
CHG CHGMAX
BAT
MX8903A-EGHJN/Y
FLT = HIGH IMPEDANCE
V
< V < V
BAT BATREG
BATPQ
I
≤ I
CHG CHGMAX
I
< I
CHG TERM
AND V = V
BAT
BATREG
I
> I
CHG TERM
AND THERMAL
OR INPUT LIMIT
NOT EXCEEDED;
RESET TIMER
RESET TIMER
ANY CHARGING
STATE
TOP-OFF
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
THM OK
TIMER RESUME
THM NOT OK
TIMER SUSPEND
V
BAT
< V
+ V
BATREG RSTRT
RESET TIMER
V
= V
BATREG
BAT
I
= I
CHG TERM
TEMPERATURE SUSPEND
= 0mA
UOK OR DOK PREVIOUS STATE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
I
CHG
TIMER > t
TOP-OFF
DONE
UOK AND/OR DOK = 0
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
V
+ V < V < V
RSTRT BAT BATREG
BATREG
I
= 0mA
CHG
图6．MAX8903A充电状态流程图
C
快充模式下，较重的系统负载或器件的自发热可能引起
MAX8903_降低充电电流。这种情况下，如果充电电流下
降到所设置的快充电流的50%，快充定时器的计时速率将
降低2倍；如果充电电流下降到所设置的快充电流的20%
时，定时器进入挂起状态。如果充电器使BAT电压达到
VBATREG (即充电器进入恒压模式)，快充定时器将不受任
何电流的影响。
CT
t
= 33min ×
PREQUAL
0.15µF
C
CT
t
= 660min×
FST -CHG
0.15µF
t
t
= 15s (MAX8903A/D/H/J/N/Y)
TOP-OFF
TOP-OFF
C
CT
= 132min×
(MAX8903B/E/G)
0.15µF
20
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
CEN
VL
VL
THERMISTOR
CIRCUITRY
MAX8903_
MAX8903B/MAX8903E/
MAX8903G ONLY
THERMISTOR
DETECTOR
0.87 VL
R
TB
ALTERNATE
THERMISTOR
CONNECTION
0.74 VL
COLD
THM
R
TS
THM
OUT OF
RANGE
0.28 VL
HOT
R
TP
R
T
DISABLE
CHARGER
ENABLE THM
0.03 VL
R
T
ALL COMPARATORS
60mV HYSTERESIS
GND
图7．热敏电阻监测电路
热敏电阻输入(THM)
表3．不同热敏电阻对应的故障温度
THM输入在外部连接一个负温度系数(NTC)的热敏电阻，
用于监测电池或系统温度。当热敏电阻温度超过所限制的
范围时，充电器处于挂起模式。充电计时器为挂起状态，
并将保持该状态而不产生故障指示。当热敏电阻恢复到限
定范围时，重新开始充电，充电定时器从停止处重新开始
计时。将THM接GND则禁用热敏电阻监测功能，表3所示
为不同热敏电阻的故障温度。
Thermistor β (K)
(kΩ) (Figure 7)
3000 3250 3500 3750 4250
R
10
10
10
10
10
TB
Resistance at +25°C
(kΩ)
10
10
10
10
10
Resistance at +50°C
(kΩ)
4.59
4.30
4.03
3.78 3.316
由于热敏电阻监测电路在THM和VL之间引入了一个外部
Ω (+25°C时)。
偏置电阻(RTB，图7)，热敏电阻无需局限于10k
只要偏置电阻等于热敏电阻在 25 C时的阻值，即可使用
Resistance at 0°C (kΩ) 25.14 27.15 29.32 31.66 36.91
Nominal Hot Trip
Temperature (°C)
+
°
+
55
-3
53
-1
50
0
49
2
46
°
Ω
任何阻值的热敏电阻。例如，对于 25 C时10k 的热敏电
Nominal Cold Trip
Temperature (°C)
Ω电阻；对于+25°C时100kΩ的热敏
阻，在RTB处使用10k
电阻，则使用100kΩ电阻。
4.5
+
°
Ω
对于典型的10kΩ ( 25 C时)热敏电阻和10k RTB电阻，当
热敏电阻下降到3.97kΩ以下(过热)或上升到28.7kΩ以上(过
冷)时，充电器进入温度挂起状态。相当于使用β为3500的
VL稳压器
VL是一个5V线性稳压器，为MAX8903的内部电路供电，
并为BST电容充电。VL在外部为电池的热敏电阻提供偏
置。VL由USB或DC输入电源供电，当USB和DC端均连接
电源时，VL由DC电源供电。当USB或DC的输入电压高于
1.5V左右时，VL使能。输入电压高于过压门限时，VL不
会关断。同样，当充电器关闭(CEN = 高电平)时，VL也不
°
+
°
10kΩ NTC热敏电阻，温度处于0 C至 50 C范围。热敏电
阻与温度的通用关系式由下式定义：
1
1
β
−
T+273°C
298°C
R
= R × e
25
μ
会关断。在VL与GND之间连接一个1 F电容。
T
21
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
式中：
功耗
RT = 温度为T (摄氏度)时，热敏电阻的阻值(Ω)
表4. 封装热特性
+ °
Ω
= 25 C时，热敏电阻的阻值( )
R25
28-PIN 4mm x 4mm THIN QFN
β = 热敏电阻的材料常数，典型值处于3000K至5000K
SINGLE-LAYER PCB
MULTILAYER PCB
°
T = 热敏电阻的检测温度( C)
1666.7mW
2286mW
Continuous
Power
Dissipation
表3给出了不同热敏电阻材料常数对应的MAX8903_ THM
温度限制。
Derate 20.8mW/°C
above +70°C
Derate 28.6mW/°C
above +70°C
有些设计可能选择其它热敏电阻温度限值。通过改变RTB
用一个电阻与热敏电阻串联和/或并联，或使用β值不同
的热敏电阻，都可以调节温度温度门限。例如，使用β值
为4250的热敏电阻，并联一个120kΩ的电阻，可以得到
，
θ
θ
48°C/W
3°C/W
35°C/W
3°C/W
JA
JC
+
°
°
°
+
45 C的高温门限和0 C的低温门限。由于热敏电阻阻值
最小SYS输出电容
°
在0 C左右时远远高于 50 C对应的阻值，并联一个大电
阻可以降低低温门限，而对高温门限的降低很小。相反，
串联一个小电阻可以提升高温门限，而对低温门限的提升
很小。加大RTB可降低低温门限和高温门限，减小RTB则会
提高两个门限。
根据MAX8903_版本的不同，SYS负载调整率为25mV/A或
40mV/A。25mV/A版本增大了反馈环路增益，因而具有更
好的负载调整特性。为确保具有较高增益的反馈环路稳定
工作，需使用一个较大的SYS输出电容。具有25mV/A SYS
MX8903A-EGHJN/Y
μ
负载调整率的器件需要22 F SYS输出电容，而具有40mV/A
SYS负载调整率的器件仅需要10 F SYS输出电容。关于
MAX8903_不同版本的更多信息，请参见表6。
值得注意的是只要有效电源连接至DC或USB，即使禁止
充电时(CEN = 高电平)，由于VL有效，热敏电阻将始终流
过偏置电流。使用10kΩ热敏电阻，且VL采用10kΩ上拉电
μ
μ
Ω
DC-DC降压调节器的电感选择
MAX8903_的控制架构需使用一个1.0μH至10μH外部电感
(LOUT)，以确保正常工作。本节对控制架构和电感选择进
行了说明。表5给出了典型应用的推荐电感选择。如在针
对特定应用选择最佳电感的计算过程中需要帮助，请参
见以下网址的电子表格：china.maxim-ic.com/design/
tools/calculators/files/MAX8903-INDUCTOR-
DESIGN.xls。
阻时，会产生额外的250 A负载。如果选择100k 热敏电
μ
阻和100kΩ上拉电阻，该负载可降至25 A。
电池检测的供电使能控制
电池检测功能的供电使能控制允许MAX8903B/MAX8903E/
MAX8903G在施加/移除电池时自动使能/禁用USB和DC
电源输入。该功能采用电池组的集成热敏电阻作为检测
元件，判断何时施加或移除电池。利用该功能，基于
MAX8903B/MAX8903E/MAX8903G的系统可在电池移除
时关断，而与USB或DC电源输入是否有外部电源无关。
MAX8903 DC-DC降压调节器采用恒定开关频率(fSW)的
控制架构，当输入电压降低至接近输出电压时，采用高
占空比工作方式，受最小关断时间(tOFFMIN)的限制，器件
可以工作在低于fSW的频率。工作在高占空比条件时，调
节器采用具有最小关断时间tOFFMIN的峰值电流控制架构。
类似地，当输入电压较大时，受最小导通时间(tONMIN)的
限制，工作频率无法达到fSW，此时调节器采用最小导通
时间固定的谷电流控制架构。
MAX8903B/MAX8903E/MAX8903G在热敏电阻检测比较
器上使用电池检测供电使能控制的电路如图7所示。如果
没有链接电池，则不存在热敏电阻，THM将通过RTB上拉
至VL。当THM的引脚电压上升到VL的87%以上时，则认
为电池已经被移除，系统关断。也可以完全旁路该热敏电
阻检测电路，这种情况下，允许系统在电池移除后继续采
用外部电源供电。如果将THM引脚连接至GND (THM端
的电压低于VL的3%)，则禁用热敏电阻检测功能，系统不
会响应热敏电阻输入的变化。这种情况下，假定系统自身
具有温度检测功能，当温度超出安全充电范围时，停止由
CEN输入引起的充电状态变化。
fSW = 4MHz的MAX8903器件版本具有最小的LOUT，在输
入电压较低(5V或9V)时具有较高效率。对于输入电压较高
(12V)的应用，fSW = 1MHz的MAX8903G因其更高的效率
而成为最佳选择。
22
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
对于给定的输出电压最大值，若最小输入电压允许调节器
保持fSW工作频率，则输入电压最小时电感纹波电流最小。
如果输入电压最小值限定的开关关断时间小于tOFFMIN，则
调节器在即将进入固定最小关断时间工作模式时具有最小
的电感纹波电流。为了使工作在电流模式的调节器具有低
抖动和稳定的占空比系数，在电感纹波电流处于最小值时
电感的纹波电流最小值(IL_RIPPLE_MIN)应大于150mA。由
V
1
f
SW
SYS(MIN)
(5)
t
= t
if
×
≤ t
ONMIN
,
ON
ONMIN
V
DC(MAX)
否则
V
1
SYS(MIN)
t
=
×
ON
V
f
下面的式(1)和式(2)计算所允许的输出电感最大值LOUT_MAX
。
DC(MAX)
SW
V
1
f
SW
SYS(MAX)
电感饱和直流电流额定值(ISAT)必须大于直流降压输出限流
值(ISDLIM)与二分之一最大纹波电流值之和，如式(6)所示。
(1) t
= t
if 1−
×
≤ t
,
OFF
OFFMIN
OFFMIN
V
DC(MIN)
IL
否则
RIPPLE _MAX
(6)
I
> I
+
SAT
SDLIM
2
V
1
SYS(MAX)
t
= 1−
×
OFF
V
f
DC(MIN)
SW
其中，ILRIPPLE_MAX为由式(7)和(8)计算得到的纹波电流中
数值较大的一个。
其中，tOFF为关断时间，VSYS(MAX)为充电器输出电压最大
值，VDC(MIN)为最小直流输入电压。
V
× t
OFF
SYS(MAX)
(7)
(8)
IL
=
RIPPLE_MIN_ T
OFF
L
OUT
V
× t
SYS(MAX)
OFF
L
=
(2)
OUT _MAX
I
L _RIPPLE _MIN
V
− V
× t
ON
(
)
DC(MAX)
SYS(MIN)
IL
=
RIPPLE _MIN_ T
ON
L
其中，LOUT_MAX为所允许的最大电感值。
OUT
为选取一个磁芯损耗符合要求且能够在指定fSW工作频率
下保证无抖动稳定工作的小尺寸电感，可以首先设置适当
的纹波系数K，并在式(2)、(3)和(4)给出的范围内选取电感
值，从而确定实际的输出电感LOUT。LOUT不应低于表6列
出的最小电感值。对于(2A ≥ ISDLIM ≥ 1A)的工作条件，
推荐的纹波系数范围为(0.2 ≤ K ≤ 0.45)。
PCB布局和布线
良好的布线设计有助于降低地电位的偏差和接地平面的电
压梯度，这些因素会导致系统不稳定或稳压误差。GND和
PG仅通过一个点连接至功率地，使功率地电流的影响最
小。电池地应该直接连接到功率地。ISET和IDC电流设置
电阻应直接连接到GND，避免电流误差。将GND直接连
接到IC下方的裸焊盘。在裸焊盘下方使用多个过孔接地，
有助于IC散热。DC、SYS、BAT及USB至功率地的输入电
容应尽量靠近IC放置。尽可能采用短而宽的布线作为大电
流引线，例如DC、SYS和BAT的连线。关于PCB布局实例，
请参考MAX8903A评估板的数据资料。
V
× t
SYS(MAX)
OFF
L
=
(3)
OUT _MIN _ T
OFF
K × I
SDLIM
其中，tOFF是由式(1)得到的最小关断时间。
V
− V
SYS(MIN)
× t
(
)
DC(MAX)
ON
(4)
L
=
OUT _MIN _ t
ON
K × I
SDLIM
其中，VDC(MAX)为最大输入电压，VSYS(MIN)为充电器输出
电压最小值，tON为输入电压较大时的导通时间，可由下
式计算得出：
23
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
表5. 推荐电感示例
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
DC INPUT
VOLTAGE
RANGE
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
(I
)
SDMAX
±.1µH, IFSC±118ABER±R1M1±, Vishay
2.5mm x 2mm x ±.2mm, 43mΩ (max), 2.6A
or ±.1µH, LQH32PN±R1-NN1, Murata,
3.2mm x 2.5mm x ±.55mm, 54mΩ (max), 2.3A
5V ±±10
5V ±±10
5V ±±10
5V ±±10
9V ±±10
9V ±±10
2A
MAX8913H/J/N/Y, 4MHz
MAX8913H/J/N/Y, 4MHz
±.5µH inductor, MDT2521-CN±R5M, TOKO
2.5mm x 2.1mm x ±.2mm, ±23.5mΩ (max), ±.25A
or ±.5uH Inductor, IFSC±118ABER±R5M1±, Vishay
2.5mm x 2mm x ±.2mm, 72mΩ (max), 2.2A
±A
2A
±A
2A
±A
2.2µH inductor, DFE3225±2C-2R2N, TOKO
3.2mm x 2.5mm x ±.2mm, 9±mΩ (max), 2.4A
or 2.2µH inductor, IFSC±5±5AHER2R2M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 45mΩ (max), 3A
MAX8913A/B/C/D/E,
4MHz
MX8903A-EGHJN/Y
2.2µH inductor, IFSC±118ABER2R2M1±, Vishay
2.5mm x 2mm x ±.2mm, 91mΩ (max), 2.±5A
or 2.2µH Inductor, LQH32PN2R2-NN1, Murata
3.2mm x 2.5mm x ±.55mm, 9±mΩ (max), ±.55A
MAX8913A/B/C/D/E,
4MHz
±.5uH inductor, IFSC±118ABER±R5M1±, Vishay
2.5mm x 2mm x ±.2mm, 72mW (max), 2.2A
or ±.5µH Inductor, VLS41±2ET-±R5N, TDK
4mm x 4mm x ±.2mm, 72mW (max), 2.±A
MAX8913H/J/N/Y, 4MHz
MAX8913H/J/N/Y, 4MHz
2.2µH inductor, IFSC±118ABER2R2M1±, Vishay
2.5mm x 2mm x ±.2mm, 91mΩ (max), 2.±5A
or 2.2µH inductor, LQH3NPN2R2NJ1, Murata
3mm x 3mm x ±.±mm, 83mΩ (max), ±.±5A
24
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
表5. 推荐电感示例(续)
DC STEP-DOWN
DC INPUT
PART NUMBER,
SWITCHING
FREQUENCY*
OUTPUT
VOLTAGE
RECOMMENDED INDUCTOR
CURRENT LIMIT
RANGE
(I
)
SDMAX
2.2µH inductor, DFE3225±2C-2R2N, TOKO
3.2mm x 2.5mm x ±.2mm, 9±mΩ (max), 2.4A
or 2.2µH Inductor, IFSC±5±5AHER2R2M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 45mΩ (max), 3A
MAX8913A/B/C/D/E,
4MHz
9V ±±10
9V ±±10
9V ±±10
9V ±±10
±2V ±±10
±2V ±±10
2A
2.2µH Inductor, IFSC±118ABER2R2M1±, Vishay
2.5mm x 2mm x ±.2mm, 91mΩ (max), 2.±5A
or 2.2µH Inductor, LQH3NPN2R2NJ1, Murata
3mm x 3mm x ±.±mm, 83mΩ (max), ±.±5A
MAX8913A/B/C/D/E,
4MHz
±A
2A
±A
2A
±A
4.3uH Inductor, DEM45±8C (±235AS-H-4R3M), TOKO
4.7mm x 4.5mm x ±.8mm, 84mΩ (max), 2.1A
or 4.7µH Inductor, IFSC±5±5AHER4R7M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 91mΩ (max), 2.1A
MAX8913G, ±MHz
MAX8913G, ±MHz
MAX8913G, ±MHz
MAX8913G, ±MHz
4.7µH inductor, DEM28±8C (±227AS-H-4R7M), TOKO
3.2mm x 2.8mm x ±.8mm, 92mΩ (max), ±.±A
or 4.7µH inductor, IFSC±118ABER4R7M1±, Vishay
2.5mm x 2mm x ±.2mm, 2±2mΩ (max), ±.2A
4.3µH inductor, DEM45±8C (±235AS-H-4R3M), TOKO
4.7mm x 4.5mm x ±.8mm, 84mΩ (max), 2.1A
or 4.7µH inductor, IFSC±5±5AHER4R7M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 91mΩ (max), 2.1A
6.8µH, IFSC±5±5AHER6R8M1±, Vishay
3.8mm x 3.8mm x ±.8mm, ±±5mΩ (max), ±.5A
or 6.8µH, LQH44PN6R8MP1, Murata
4mm x 4mm x ±.65mm, ±44mΩ (max), ±.34A
*关于器件型号的更多信息，请参见选型指南。
25
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MAX8903H/MAX8903J/MAX8903N/MAX8903Y的基本架
构和功能是相同的，不同之处在于具体的电气参数和工作
参数。表6列出了各器件版本之间的不同之处。
选型指南
MAX8903_提供不同版本的器件，采用固定器件型号后的第
一个字母进行区分。MAX8903A-MAX8903E/MAX8903G/
表6. 选型指南
PARAMETER MAX8903A MAX8903B MAX8903C MAX8903D MAX8903E MAX8903G MAX8903H MAX8903J MAX8903N MAX8903Y
Minimum SYS
Regulation
3.0V
3.0V
3.4V
3.4V
3.0V
3.0V
3.4V
3.4V
3.4V
3.0V
Voltage
(V
)
SYSMIN
SYS Regulation
Voltage
4.4V
4.325V
2.2µH
4.4V
4.4V
4.325V
2.2µH
4.325V
2.2µH
4.4V
1µH
4.5V
1µH
4.4V
1µH
4.4V
1µH
(V
SYSREG
)
Minimum
Allowable
Inductor
2.2µH
2.2µH
2.2µH
MX8903A-EGHJN/Y
Switching
4MHz
4MHz
4MHz
4MHz
4MHz
1MHz
4MHz
4MHz
4MHz
4MHz
Frequency
SYS Load
Regulation
40mV/A
25mV/A
40mV/A
40mV/A
25mV/A
25mV/A
40mV/A
25mV/A
25mV/A
25mV/A
Minimum SYS
Output
10µF
4.2V
22µF
4.2V
10µF
4.2V
10µF
4.1V
22µF
4.1V
22µF
4.2V
10µF
4.2V
10µF
22µF
22µF
Capacitor (C
)
SYS
BAT Regulation
Voltage
4.35V
4.15V
4.15V
(V
BATREG
)
(Note 5)
BAT Prequal
Threshold
3V
2.5V
3V
3V
2.5V
2.5V
3V
3V
3V
3V
(V
BATPQ
)
(Note 5)
Top-Off Timer
(Note 6)
15s (fixed)
1mA
132min
10mA
15s (fixed) 15s (fixed)
132min
10mA
132min
10mA
15s (fixed) 15s (fixed) 15s (fixed) 15s (fixed)
VL Output
Current Rating
1mA
1mA
1mA
1mA
1mA
1mA
Power-Enable
On Battery
Detection
No
—
Yes
—
No
—
No
—
Yes
—
Yes
—
No
No
—
No
—
No
—
(Note 7)
Comments
(Note 8)
注5：典型值，最小/最大值参见电气特性表。
注6：该变化也会更改预均衡和快充定时器的时间设置。
注7：详细信息请参见电池检测的供电使能控制部分。
注8：MAX8903H是MAX8903C的新版本，推荐用于新设计。
26
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
引脚配置
芯片信息
PROCESS: BiCMOS
TOP VIEW
21 20 19 18 17 16 15
14
13
22
CEN
ISET
CHG
SYS 23
12 GND
24
25
26
27
28
SYS
CS
CS
LX
MAX8903_
IDC
CT
11
10
9
VL
EP
8
DOK
LX
+
1
2
3
4
5
6
7
TQFN
27
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
封装信息
如需最近的封装外形信息和焊盘布局(占位面积)，请查询china.maxim-ic.com/packages。请注意，封装编码中的“+”、“#”或“-”
仅表示RoHS状态。封装图中可能包含不同的尾缀字符，但封装图只与封装有关，与RoHS状态无关。
封装类型
封装编码
外形编号
焊盘布局编号
21-0139
90-0035
28 TQFN-EP
T2844-1
MX8903A-EGHJN/Y
28
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
MX8903A-EGHJN/Y
封装信息(续)
如需最近的封装外形信息和焊盘布局(占位面积)，请查询china.maxim-ic.com/packages。请注意，封装编码中的“+”、“#”或“-”
仅表示RoHS状态。封装图中可能包含不同的尾缀字符，但封装图只与封装有关，与RoHS状态无关。
29
+
2A单节Li 电池DC-DC充电器，
用于USB和适配器供电系统
修订历史
修订号
修订日期
12/08
8/09
说明
修改页
—
0
1
2
3
4
5
最初版本。
在数据资料中增加了MAX8903C/MAX8903D。
做了多处修正。
1–20
11/09
10/10
5/11
1–7, 9, 11–21
1–29
增加了MAX8903B、MAX8903E、MAX8903G和MAX8903Y。
增加了MAX8903H和MAX8903J，更新了元件值。
增加了MAX8903N，删除了MAX8903J的未来产品标识。
1–29
9/11
1–29
MX8903A-EGHJN/Y
Maxim北京办事处
北京8328信箱 邮政编码100083
免费电话：800 810 0310
电话：010-6211 5199
传真：010-6211 5299
Maxim不对Maxim产品以外的任何电路使用负责，也不提供其专利许可。Maxim保留在任何时间、没有任何通报的前提下修改产品资料和规格的权利。电气
特性表中列出的参数值(最小值和最大值)均经过设计验证，数据资料其它章节引用的参数值供设计人员参考。
30
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
©
2011 Maxim Integrated Products Maxim是Maxim Integrated Products，Inc.的注册商标。
MAX8903A, MAX8903B, MAX8903C, MAX8903D, MAX8903E, MAX8903G, MAX8903H, MAX8903J, MAX8903N, MAX8903Y 2A 1节Li+电池DC-DC充电器，用于USB和适配器供电系统 - 概述
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Maxim > 产品 > 电源和电池管理 > MAX8903A, MAX8903B, MAX8903C, ...
MAX8903A, MAX8903B, MAX8903C, MAX8903D, MAX8903E, MAX8903G, MAX8903H, MAX8903J,
MAX8903N, MAX8903Y
2A 1节Li+电池DC-DC充电器，用于USB和适配器供电系统
工作在4MHz开关频率
概述
技术文档
定购信息 相关产品 用户说明 (0) 所有内容
状况
数据资料
状况
：生产中。
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Rev. 5 (PDF, 1.3MB)
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中文
Rev. 5 (PDF, 3MB)
概述
E-Mail
MAX8903A–MAX8903E/MAX8903G/MAX8903H/MAX8903J/MAX8903Y是
和Smart Power Selector™ (智能电源选择器)，工作于双电源输入(交流适配器和USB)。开关模式充电器工作在高
开关频率，可省去散热器并允许使用小尺寸外部元件。该器件可采用独立的USB电源或交流适配器供电，也可以
用一个输入端接收两路电源输入。芯片集成了所有充电功能和用于切换电池、外部电源、负载的功率开关。无需外
部MOSFET、反向保护二极管和检流电阻。
一款集成的单节Li+电池充电器
MAX8903_具有经过优化的智能功率控制
和SYS输出限流均可独立设置。在保证系统供电的前提下为电池充电。充电电流和SYS输出限流可设置在最
高2A，USB输入限流可设置在100mA或500mA。输入选择电路可自动地将系统供电电源从电池切换至外部电源
器件工作在4.15V至16V直流输入电压范 ，输入端具有高达20V的保护；USB输入范 为4.1V至6.3V，输入端具
有最高8V的保护。
功能，可充分利用有限的USB或适配器电源的供电能力。电池充电电流
。
围
围
未接输入电源
预充检测及定时器、快充定时器、过压保护、充电状态指示和故障指示输出、电源就绪监视器以及电池热敏电阻检
测。此外，片内热管理电路可以根据需要降低电池充电速率或交流适配器的充电电流，以防止充电器过
热。MAX8903_采用4mm x 4mm、28引脚薄型 QFN封装。
时，MAX8903_内部电路可以阻止电流从电池、系统向直流电源、USB输入倒灌。其它功能还包括
不同
版本的MAX8903_提高了设计灵活性，便于选择不同的系统电源电压、电池预检验门限和电池满充电
压。MAX8903B/MAX8903E/MAX8903G的电池检测功能还包含供电使能控制，详细信息请参考完整数据资料中
的选型 指南部分。
http://china.maxim-ic.com/datasheet/index.mvp/id/6019[2012-07-09 8:43:44]
MAX8903A, MAX8903B, MAX8903C, MAX8903D, MAX8903E, MAX8903G, MAX8903H, MAX8903J, MAX8903N, MAX8903Y 2A 1节Li+电池DC-DC充电器，用于USB和适配器供电系统 - 概述
MAX8903支持低温、快速
充电
现备有评估板：MAX8903AEVKIT
关键特性
应用/使用
高效DC-DC转换器，无需散热器
移动互联网设备
PDA、掌 上电脑
个人导航设备
便携式多媒体播放器
智能蜂窝电话
50mΩ系统至电池开关导
4MHz开关频率，允许使用小尺寸外部元件
立即开启—可在无电池或低电池电压下工作
和无线手持装置
两路限流
适配器/USB/电池供电自动切换，支持瞬变负载
通电阻
输入—交流适配器或USB
超便携移动PC
支持USB规范
热敏电阻检测
集成检流电阻
无需外部MOSFET或二极管
4.1V至16V输入工作电压范
围
关键特性:
Battery Chargers
Smallest
Available
Pckg.
Protected
IN
(V)
Charging
IN
(V)
Max.
CHG
(A)
V
V
I
Budgetary Price
Lithium
Ion
Cells
Charge
Rate
Set by
Part
Number
Cell
Chemistry
Charge
Termination
Charge
Regulation
EV
Kit
Oper. Temp.
(°C)
Package/Pins
2
(mm
)
max
w/pins
max
max
≥
See Notes
MAX8903A
MAX8903B
MAX8903C
MAX8903D
TQFN/28
TQFN/28
TQFN/28
TQFN/28
$2.74 @1k
$2.74 @1k
$2.74 @1k
$2.74 @1k
Li-Ion
Li-Polymer
Preset
Resistor
Min. Charge
Current
1
20
16
2
Switchmode
Yes
-40 to +85
16.8
查看所有Battery Chargers (70)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may
differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized
distributor.
图表
http://china.maxim-ic.com/datasheet/index.mvp/id/6019[2012-07-09 8:43:44]
MAX8903A, MAX8903B, MAX8903C, MAX8903D, MAX8903E, MAX8903G, MAX8903H, MAX8903J, MAX8903N, MAX8903Y 2A 1节Li+电池DC-DC充电器，用于USB和适配器供电系统 - 概述
典型 工作电路
更多信
息
新品
发布
[ 2009-06-29 ]
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注释、注解
参考文献： 19-4410 Rev. 5; 2011-10-04
本页最后一次更新: 2011-10-04
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© 2012 Maxim Integrated Products版权所有
http://china.maxim-ic.com/datasheet/index.mvp/id/6019[2012-07-09 8:43:44]
19-4410; Rev 5; 9/11
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
General Description
Features
o Efficient DC-DC Converter Eliminates Heat
The MAX8903A–MAX8903E/MAX8903G/MAX8903H/
MAX8903J/MAX8903N/MAX8903Y are integrated 1-cell
Li+ chargers and Smart Power Selectors™ with dual
(AC adapter and USB) power inputs. The switch mode
charger uses a high switching frequency to eliminate
heat and allow tiny external components. It can operate
with either separate inputs for USB and AC adapter
power, or from a single input that accepts both. All
power switches for charging and switching the load
between battery and external power are included on-
chip. No external MOSFETs, blocking diodes, or cur-
rent-sense resistors are required.
o 4MHz Switching for Tiny External Components
o Instant On—Works with No/Low Battery
o Dual Current-Limiting Inputs—AC Adapter or USB
Automatic Adapter/USB/Battery Switchover to
Support Load Transients
50mΩ System-to-Battery Switch
Supports USB Spec
o Thermistor Monitor
o Integrated Current-Sense Resistor
o No External MOSFETs or Diodes
o 4.1V to 16V Input Operating Voltage Range
The MAX8903_ features optimized smart power control
to make the best use of limited USB or adapter power.
Battery charge current and SYS output current limit are
independently set. Power not used by the system
charges the battery. Charge current and SYS output cur-
rent limit can be set up to 2A while USB input current can
be set to 100mA or 500mA. Automatic input selection
switches the system from battery to external power. The
DC input operates from 4.15V to 16V with up to 20V pro-
tection, while the USB input has a range of 4.1V to 6.3V
with up to 8V protection.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
MAX8903AETI+T
MAX8903BETI+T
MAX8903CETI+T
MAX8903DETI+T
MAX8903EETI+T
MAX8903GETI+T
MAX8903HETI+T
MAX8903JETI+T
MAX8903NETI+T
MAX8903YETI+T
The MAX8903_ internally blocks current from the bat-
tery and system back to the DC and USB inputs when
no input supply is present. Other features include pre-
qual charging and timer, fast charge timer, overvoltage
protection, charge status and fault outputs, power-OK
monitors, and a battery thermistor monitor. In addition,
on-chip thermal limiting reduces battery charge rate
and AC adapter current to prevent charger overheat-
ing. The MAX8903_ is available in a 4mm x 4mm, 28-pin
thin QFN package.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
T = Tape and reel.
Typical Operating Circuit
The various versions of the MAX8903_ allow for design
flexibility to choose key parameters such as system
regulation voltage, battery prequalification threshold,
and battery regulation voltage. The MAX8903B/
MAX8903E/MAX8903G also includes power-enable on
battery detection. See the Selector Guide section for
complete details.
AC
ADAPTER
OR USB
LX
CS
DC
SYS
LOAD
CURRENT
CHARGE
CURRENT
CHARGE
AND
SYS LOAD
SWITCH
SYSTEM
LOAD
Applications
PDAs, Palmtops, and
Wireless Handhelds
Portable Multimedia
Players
PWM
STEP-DOWN
Personal Navigation
Devices
Smart Cell Phones
Mobile Internet Devices
Ultra Mobile PCs
BAT
BATTERY
USB
USB
MAX8903_
GND
Selector Guide appears at end of data sheet.
Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.
Pin Configuration appears at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
ABSOLUTE MAXIMUM RATINGS
DC, LX to GND .......................................................-0.3V to +20V
LX Continuous Current (total in two pins).......................2.4A
RMS
RMS
RMS
RMS
DCM to GND ..............................................-0.3V to (V
+ 0.3V)
CS Continuous Current (total in two pins) ......................2.4A
SYS Continuous Current (total in two pins) .......................3A
BAT Continuous Current (total in two pins) .......................3A
DC
DC to SYS .................................................................-6V to +20V
BST to GND ...........................................................-0.3V to +26V
BST TO LX................................................................-0.3V to +6V
USB to GND .............................................................-0.3V to +9V
USB to SYS..................................................................-6V to +9V
VL to GND ................................................................-0.3V to +6V
VL Short Circuit to GND .............................................Continuous
Continuous Power Dissipation (T = +70°C)
A
28-Pin Thin QFN-EP
Multilayer (derate 28.6mW/°C above +70°C) ..........2286mW
28-Pin Thin QFN-EP
THM, IDC, ISET, CT to GND........................-0.3V to (V + 0.3V)
VL
DOK, FLT, CEN, UOK, CHG, USUS,
Single-Layer (derate 20.8mW/°C above +70°C)...1666.7mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature Range............................-40°C to +150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
BAT, SYS, IUSB, CS to GND ................................-0.3V to +6V
SYS to BAT ...............................................................-0.3V to +6V
PG, EP (exposed pad) to GND .............................-0.3V to +0.3V
DC Continuous Current (total in two pins)......................2.4A
USB Continuous Current.......................................................1.6A
RMS
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
MX8903A–EGHJN/Y
DC INPUT
DC Operating Range
4.15
3.9
16
4.1
4.4
V
V
No valid USB input
Valid USB input
4.0
4.3
When V
goes low, V
DC
DOK
DC Undervoltage Threshold
DC Overvoltage Threshold
rising, 500mV typical hysteresis
4.0
When V goes high, V
hysteresis
rising, 500mV typical
DC
DOK
16.5
17
17.5
4
V
Charger enabled, no switching, V
= 5V
2.3
15
SYS
Charger enabled, f = 3MHz, V
= 5V
DC
DC Supply Current
mA
Charger enabled, V
Charger enabled, V
= 0V, 100mA USB mode (Note 2)
= 5V, 100mA USB mode (Note 2)
1
2
2
C EN
C EN
1
V
= 0V, V
= 5V
USUS
0.10
0.15
0.15
0.31
0.25
DCM
DC High-Side Resistance
DC Low-Side Resistance
DC-to-BAT Dropout Resistance
Ω
Ω
Ω
Assumes a 40mΩ inductor resistance (R )
L
When SYS regulation and charging stops, V
200mV hysteresis
falling,
DC
DC-to-BAT Dropout Voltage
0
15
30
mV
Minimum Off Time (t
Minimum On Time (t
)
100
70
4
ns
ns
OFFMIN
)
ONMIN
V
V
V
V
= 8V, V
= 5V, V
= 9V, V
= 9V, V
= 4V
= 3V
= 4V
= 3V
DC
DC
DC
DC
BAT
BAT
BAT
BAT
MAX8903A/B/C/D/E/H/J/Y
MAX8903G
3
Switching Frequency (f
)
MHz
SW
1
1
DC Step-Down Output Current-
Limit Step Range
0.5
2
A
R
IDC
R
IDC
R
IDC
= 3kΩ
= 6kΩ
1900
950
2000
1000
500
2100
1050
550
DC Step-Down Output Current
V
= 6V, V
= 4V
SYS
mA
DC
Limit (I
)
SDLIM
= 12kΩ
450
2
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
1
MAX
UNITS
ms
No valid USB input
DC Soft-Start Time
Valid USB input before soft-start
20
μs
DC Output Current
500mA USB Mode (Note 3)
V
V
V
= 0V, V
= 0V, V
= 5V
= 0V
= 0V
450
90
475
95
500
100
mA
mA
μA
DCM
DCM
IUSB
IUSB
DC Output Current
100mA USB Mode (Note 2)
SYS to DC Reverse Current
Blocking
= 5.5V, V
0.01
SYS
DC
USB INPUT
USB Operating Range
USB Standoff Voltage
USB Undervoltage Threshold
USB Overvoltage Threshold
4.1
6.3
8
V
V
V
V
When V
When V
goes low, V
rising, 500mV hysteresis
3.95
6.8
90
4.0
6.9
95
4.05
7.0
100
500
3
UOK
UOK
USB
goes high, V
rising, 500mV hysteresis
USB
V
V
= 0V (100mA setting)
= 5V (500mA setting)
IUSB
IUSB
USB Current Limit
mA
450
475
1.3
0.8
0.115
15
I
I
= I
= 0mA, V
= 0mA, V
= 0V
SYS
SYS
BAT
BAT
CEN
CEN
USB Supply Current
mA
= I
= 5V
2
V
= 5V (USB suspend mode)
0.25
30
USUS
Minimum USB to BAT Headroom
USB to SYS Dropout Resistance
0
mV
Ω
0.2
1
0.35
V
V
rising
ms
μs
USB
USB Soft-Start Time
falling below DC UVLO to initiate USB soft-start
20
DC
SYS OUTPUT
MAX8903A/B/E/G/Y
SYSMIN MAX8903C/D/H/J/N
MAX8903A/C/D/H/N/Y
3.0
3.4
Minimum SYS Regulation Voltage
I
V
= 1A,
< V
BAT
SYS
V
V
(V
SYSMIN
)
4.3
4.265
4.4
4.4
4.5
4.395
4.55
Regulation Voltage
I
= 0A
MAX8903B/E/G
MAX8903J
4.325
4.5
SYS
MAX8903A/C/D/H
MAX8903B/E/G/J/N/Y
40
Load Regulation
I
= 0 to 2A
mV/A
SYS
25
CS to SYS Resistance
SYS to CS Leakage
V
V
V
= 6V, V
= 5V, V
= 4V, I = 1A
0.07
0.01
0.05
Ω
μA
Ω
DC
SYS
DC
DCM
SYS
CS
= 5.5V, V
= V = 0V
CS
DC
BAT to SYS Resistance
= V
= 0V, V
= 4.2V, I = 1A
SYS
0.1
100
2.0
USB
BAT
BAT to SYS Reverse Regulation
Voltage
V
= 5V, V
= 0V, V
= 0V, I = 200mA
SYS
50
75
mV
V
USB
DC
IUSB
SYS Undervoltage Threshold
SYS falling, 200mV hysteresis (Note 4)
1.8
1.9
_______________________________________________________________________________________
3
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BATTERY CHARGER
T
T
T
T
T
T
T
T
= +25°C
4.179
4.158
4.079
4.059
4.328
4.307
4.129
4.109
-150
4.200
4.200
4.100
4.100
4.350
4.350
4.150
4.150
-100
3.0
4.221
4.242
4.121
4.141
4.372
4.394
4.171
4.192
-60
A
A
A
A
A
A
A
A
MAX8903A/B/C/G/H
MAX8903D/E
MAX8903J
= -40°C to +85°C
= +25°C
= -40°C to +85°C
= +25°C
BAT Regulation Voltage
I
= 0mA
V
BAT
(V
BATREG
)
= -40°C to +85°C
= +25°C
MAX8903Y/N
= -40°C to +85°C
Charger Restart Threshold
BAT Prequal Threshold (V
Prequal Charge Current
Change in V
from DONE to fast-charge
mV
V
BAT
MAX8903A/C/D/H/J/N/Y
MAX8903B/E/G
2.9
3.1
V
rising 180mV
BAT
)
BATPQ
hystersis
2.4
2.5
2.6
Percentage of fast-charge current set at ISET
10
%
R
ISET
R
ISET
R
ISET
= 600Ω
1800
900
2000
1000
500
2200
1100
550
MX8903A–EGHJN/Y
Fast-Charge Current
= 1.2kΩ (MAX8903A/C/D)
= 2.4kΩ
mA
450
DONE Threshold (I
)
Percentage of fast-charge, I decreasing
BAT
10
%
kΩ
TERM
R
ISET
Resistor Range
0.6
2.4
ISET Output Voltage
1.5
1.25
0.05
3
V
ISET Current Monitor Gain
BAT Leakage Current
Charger Soft-Start Time
mA/A
No DC or USB input
4
6
μA
With valid input power, V
= 5V
CEN
1.0
ms
°C
Charger Thermal Limit
Temperature
100
5
Charger Thermal Limit Gain
CHARGER TIMER
Charge current = 0 at +120°C
%/°C
Prequalification Time
Fast-Charge Time
C
C
= 0.15μF
= 0.15μF
33
660
15
min
min
s
CT
CT
MAX8903A/C/D/H/J/N/Y (fixed)
MAX8903B/E/G, C = 0.15μF
Top-Off Timer (t
)
TOP-OFF
132
min
%
CT
Timer Accuracy
-15
40
+15
60
Percentage of fast-charge current below which the timer
clock operates at half-speed
Timer Extend Current Threshold
Timer Suspend Current Threshold
50
20
%
%
Percentage of fast-charge current below which timer
clock pauses
16
24
4
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
THERMISTOR MONITOR
0.27 x
0.28 x 0.29 x
THM Threshold, Hot
When charging is suspended, 1% hysteresis
When charging is suspended, 1% hysteresis
THM function is disabled below this voltage
MAX8903B/MAX8903E/MAX8903G
V
V
V
V
V
V
V
VL
VL
VL
0.73 x
0.74 x 0.75 x
THM Threshold, Cold
V
V
V
VL
VL
VL
0.0254 0.03 x 0.036 x
x V
THM Threshold, Disabled
THM Threshold DC, USB Enable
V
V
VL
VL
VL
0.83 x
0.87 x 0.91 x
V
V
V
VL
VL
VL
THM = GND or VL;
-0.100
0.001 +0.200
0.010
T
A
= +25°C
MAX8903A/C/D/H/J/N/Y
MAX8903B/E/G
THM = GND or VL;
THM Input Leakage
μA
T
A
= +85°C
THM = GND or VL;
= -40°C to +85°C
-0.200
0.001 +0.200
T
A
THERMAL SHUTDOWN, VL, AND LOGIC I/O: CHG, FLT, DOK, UOK, DCM, CEN, USUS, IUSB
High level
1.3
V
Logic-Input Thresholds
(DCM, CEN, USUS, IUSB)
Low level
0.4
Hysteresis
50
mV
T
T
= +25°C
= +85°C
-1.000
-0.200
0.001 +1.000
0.010
A
V
= 0V to 5.5V
INPUT
(MAX8903A/C/D/H/J/N/Y)
Logic-Input Leakage Current
(CEN, USUS, IUSB)
A
μA
V
= 0V to 5.5V
INPUT
T
A
= -40°C to +85°C
0.001 +0.200
(MAX8903B/E/G)
T
T
= +25°C
= +85°C
0.001
0.01
8
1
50
1
A
Logic-Input Leakage Current
(DCM)
V
V
= 0V to 16V
DCM
μA
mV
μA
= 16V
DC
A
Sinking 1mA
Sinking 10mA
Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)
80
T
T
= +25°C
= +85°C
0.001
0.01
A
Open-Drain Output Leakage
Current, High (CHG, FLT, DOK, UOK)
V
= 5.5V
OUT
A
_______________________________________________________________________________________
5
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
= 0 to 1mA
MIN
TYP
MAX
UNITS
I
VL
4.6
5.0
5.4
(MAX8903A/C/D/H/J/N/Y)
VL Output Voltage
V
V
= V
= 6V
USB
V
DC
VL
I
= 0 to 10mA
VL
4.6
5.0
5.4
(MAX8903B/E/G)
VL UVLO Threshold
falling; 200mV hysteresis
3.2
160
15
V
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
°C
°C
Note 1: Limits are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.
A
Note 2: For the 100mA USB mode using the DC input, the step-down regulator is turned off and its high-side switch operates as a
linear regulator with a 100mA current limit. The linear regulator’s output is connected to LX and its output current flows
through the inductor into CS and finally to SYS.
Note 3: For the 500mA USB mode, the actual current drawn from USB is less than the output current due to the input/output current
ratio of the DC-DC converter.
Note 4: For short-circuit protection, SYS sources 25mA below V
= 400mV, and 50mA for V
between 400mV and 2V.
SYS
SYS
MX8903A–EGHJN/Y
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/D/E/H/J/N/Y
BATTERY CHARGER EFFICIENCY
vs. BATTERY VOLTAGE
MAX8903A/B/C/D/E/H/J/N/Y
SWITCHING FREQUENCY vs. V
MAX8903G BATTERY CHARGER
EFFICIENCY vs. BATTERY VOLTAGE
DC
100
90
100
90
80
70
60
50
40
30
20
10
0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
V
DC
= 6V
80
V
= 5V
DC
70
60
50
40
30
20
10
0
V
= 9V
V
= 3V
= 4V
DC
BAT
V
= 8V
DC
V
BAT
V
= 12V
V
DC
= 12V
I
DC
I
= 0.15A
= 1.5A
I
= 0.15A
I
= 1.5A
BAT
BATT
BATT
BAT
R
V
= 1.2kΩ
= 0V
ISET
CEN
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
4
6
8
10
12
14
16
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
DC VOLTAGE (V)
6
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/D/E/H/J/N/Y
MAX8903G SYS EFFICIENCY
SYS EFFICIENCY
MAX8903G SWITCHING
vs. SYS OUTPUT CURRENT
vs. SYS OUTPUT CURRENT
FREQUENCY vs. V
DC
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
V
= 1V
= 4.4V
CEN
SYS
V
= 1
CEN
V
= 16V
DC
V
= 11V
DC
V
= 12V
V
= 4V
DC
BAT
V
= 16V
DC
V
= 9V
V
= 3V
DC
BAT
V
= 6V
DC
V
DC
= 6V
R
V
= 1.2kI
= 0V
ISET
CEN
V
= 4.5V
1000
DC
1
10
100
10000
1
10
100
1000
10,000
4
6
8
10
12
14
16
SYS OUTPUT CURRENT (mA)
SYS OUTPUT CURRENT (mA)
DC VOLTAGE (V)
USB SUPPLY CURRENT
vs. USB VOLTAGE
BATTERY LEAKAGE CURRENT
vs. BATTERY VOLTAGE
USB SUPPLY CURRENT
vs. USB VOLTAGE (SUSPEND)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
80
70
60
50
40
30
20
10
0
140
120
100
80
CHARGER
ENABLED
60
40
CHARGER
DISABLED
20
NO DC OR USB INPUT
USB SUSPEND
0
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
USB VOLTAGE (V)
BATTERY VOLTAGE (V)
USB VOLTAGE (V)
CHARGE CURRENT
vs. BATTERY VOLTAGE—USB MODE
BATTERY LEAKAGE CURRENT
vs. AMBIENT TEMPERATURE
CHARGE CURRENT
vs. BATTERY VOLTAGE—DC MODE
500
450
400
350
300
250
200
150
100
50
90
80
70
60
50
40
30
20
10
0
1200
1000
800
600
400
200
0
CHARGER ENABLED
CHARGE ENABLED
I
I
SET TO 1A
SET TO 2A
I
SET TO 1.5A
BAT
BAT
MAX8903D
DC
MAX8903A/C/H
RISING
V
BAT
RISING
V
BAT
V
= V
USB
IUSB
V
= 0V
IUSB
NO DC OR USB INPUT
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1.5
2.0
2.5
3.0
3.5
4.0
4.5
-40
-15
10
35
60
85
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
TEMPERATURE (°C)
_______________________________________________________________________________________
7
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
NORMALIZED BATTERY
REGULATION VOLTAGE
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. USB VOLTAGE
NORMALIZED CHARGE CURRENT
vs. AMBIENT TEMPERATURE
1.015
vs. AMBIENT TEMPERATURE
100.5
100.4
100.3
100.2
100.1
100.0
99.9
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
V
V
= 5V
= 0V
= 0V
V
= 5V, V = 4V
BAT
CEN
BAT
DC
USB
1.010
1.005
1.000
0.995
0.990
0.985
V
FALLING
USB
V
RISING
USB
99.8
99.7
99.6
R
= 1MΩ
SYS
22ppm/°C
60 85
99.5
0
1
2
3
4
5
6
7
-40
-15
10
35
-40
-15
10
35
60
85
USB VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, DC INPUT
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. DC VOLTAGE
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, USB INPUT
MX8903A–EGHJN/Y
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
4.6
4.5
4.4
4.3
4.2
4.1
4.0
3.9
3.8
V
= 0V
MAX8903J, V = 5.75V
DC
USB
V
= 0V, V
= 4V
BATT
DC
MAX8903J, V
USB
= 5V
V
RISING
DC
MAX8903A/C/D/H, MAX8903N/Y,
MAX8903A/C/D/H, MAX8903N/Y,
= 5V = 5V
V
= 5.75V
V
= 5.75V
DC
MAX8903B/E/G,
= 5.75V
DC
V
V
USB
USB
MAX8903B/E/G,
= 5V
V
FALLING
DC
V
DC
V
USB
V
CEN
V
BAT
V
USB
= 5V
= 0V
= 0V
MAX8903_, V = 0V
DC
MAX8903_, V = 0V
USB
0
0.5
1.0
1.5
2.0
0
2
4
6
8
10 12 14 16 18
0
100
200
300
400
500
SYS OUTPUT CURRENT (A)
DC VOLTAGE (V)
SYS OUTPUT CURRENT (mA)
CHARGE PROFILE—1400mAh BATTERY
VL VOLTAGE vs. DC VOLTAGE
ADAPTER INPUT—1A CHARGE
MAX8903A toc17
6
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
I
SET TO 1A
SET TO 2A
DC
I
BAT
5
4
3
2
1
0
V
BAT
VL WITH
NO LOAD AND
DCDC OFF
VL AND DCDC
WITH
FULL LOAD
(V
USUS
= 5V)
(V
USUS
= 0V)
I
BAT
V
= 3.6V
BAT
V
= 0V
USB
MAX8903A/B/C/G/H
0
2
4
6
8
10 12 14 16 18 20
0
20
40
60
80
100 120 140
DC VOLTAGE (V)
TIME (min)
8
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/G/H
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
CHARGE PROFILE—1400mAh BATTERY
USB INPUT—500mA CHARGE
WAVEFORMS—LIGHT LOAD
MAX8903A toc19
MAX8903A toc18
5.0
0.50
4.5
4.0
3.5
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
20mV/div
AC-COUPLED
V
OUT
V
BAT
5V/div
0V
3.0
2.5
2.0
1.5
1.0
0.5
0
V
LX
LX
I
BAT
I
MAX8903A/MAX8903B/MAX8903C
SET TO 500mA
500mA/div
0A
I
USB
R
= 44Ω
SYS
I
SET TO 2A
BAT
200ns/div
0
20 40 60 80 100 120 140 160 180 200
TIME (min)
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
WAVEFORMS—LIGHT LOAD
MAX8903A toc20
MAX8903A toc19a
20mV/div
50mV/div
AC-COUPLED
AC-COUPLED
V
V
SYS
OUT
V
= 9V, L = 2.2μH
DC
C
R
= 22μF,
= 44I
SYS
SYS
5V/div
0V
V
I
V
10V/div
LX
LX
0V
1A/div
LX
I
LX
0A
500mA/div
0A
R
= 5Ω
SYS
200ns/div
1μs/div
DC CONNECT WITH
USB CONNECTED (R = 25Ω)
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
SYS
MAX8903A toc21
MAX8903A toc20a
3.6V
2V/div
V
SYS
50mV/div
V
SYS
AC-COUPLED
V
= 9V, L = 2.2μH
I
DC
DC
500mA/div
347mA
C
= 22μF, R = 5I
SYS
SYS
CEN = 1
10V/div
0V
475mA
500mA/div
V
I
LX
I
USB
-I = CHARGING
BAT
0A
I
-335mA
BAT
500mA/div
LX
1A/div
0A
200μs/div
1μs/div
_______________________________________________________________________________________
9
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
DC CONNECT WITH NO USB
DC DISCONNECT WITH NO USB
(R = 25Ω)
(R
= 25Ω)
SYS
SYS
MAX8903A toc22
MAX8903A toc23
3.84V
3.68V
3.6V
3.6V
3.6V
3.6V
2V/div
5V/div
2V/div
5V/div
V
V
SYS
SYS
3.44V
V
V
BAT
BAT
C
DC
C
SYS
CHARGING
CHARGING
850mA
1A/div
1A/div
1A/div
1A/div
I
0A
0A
DC
850mA
-1A
I
DC
-I = CHARGING
BAT
I
BAT
I
144mA
BAT
144mA
-I = CHARGING
BATTERY
CHARGER
SOFT-START
-1A
BAT
400μs/div
40μs/div
MX8903A–EGHJN/Y
MAX8903A/C/D/H SYS LOAD TRANSIENT
MAX8903B/E SYS LOAD TRANSIENT
MAX8903A toc24a
MAX8903A toc24b
MAX8903B
V
DC
= 10.5V
L = 2.2μH
4.400V
C
= 22μF
SYS
MAX8903A
V
4.325V
R
= 3kI (2A)
SYS
IDC
20mV/div
AC-COUPLED
V
= 10.5V
DCM = HIGH
CEN = 1
DC
V
I
SYS
4.360V
1A
20mV/div
L = 2.2μH
4.305V
C
= 10μF
SYS
R
= 3kI (2A)
IDC
1A
DCM = HIGH
CEN = 1
I
SYS
SYS
500mA/div
0A
0A
500mA/div
0A
0A
100μs/div
100μs/div
USB CONNECT WITH NO DC
(R
= 25Ω)
MAX8903G SYS LOAD TRANSIENT
SYS
MAX8903A toc25
MAX8903A toc24c
3.6V
3.75V
2V/div
5V/div
V
4.325V
= 9V
SYS
3.5V
USB
5V
4.305V
50mV/div
V
SYS
V
USB
V
DC
C
L = 2.2μH
CHARGING
475mA
C
= 22μF
SYS
500mA/div
500mA/div
R
= 3kI (2A)
IDC
1A
I
USB
DCM = 1
CEN = 1
I
SYS
I
BAT
144mA
BATTERY
CHARGER
SOFT-START
500mA/div
0A
0A
-330mA
400μs/div
100μs/div
10 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
USB DISCONNECT WITH NO DC
(R
= 25Ω)
USB SUSPEND
USB RESUME
SYS
MAX8903A toc26
MAX8903A toc27
MAX8903A toc28
0V
0V
3.6V
3V
3V
V
V
2V/div
5V/div
5V/div
5V/div
USUS
USUS
V
SYS
C
USB
CHARGING
500mA/div
500mA/div
V
USB
475mA
475mA
3.6V
5V
I
0A
0A
USB
I
USB
475mA
3.8V
3.6V
V
V
SYS
SYS
500mA/div
500mA/div
2V/div
2V/div
3.7V
I
USB
I
I
BAT
BAT
-330mA
144mA
I
BAT
0A
-475mA
-475mA
0A
BATTERY
CHARGER
500mA/div
500mA/div
SOFT-START
100μs/div
200μs/div
200μs/div
Pin Description
PIN
NAME
FUNCTION
Power Ground for Step-Down Low-Side Synchronous n-Channel MOSFET. Both PG pins must be
connected together externally.
1, 2
PG
DC Power Input. DC is capable of delivering up to 2A to SYS. DC supports both AC adapter and USB
inputs. The DC current limit is set through DCM, IUSB, or IDC depending on the input source used. See
Table 2. Both DC pins must be connected together externally. Connect at least a 4.7μF ceramic capacitor
from DC to PG.
3, 4
DC
Current-Limit Mode Setting for the DC Power Input. When logic-high, the DC input current limit is set by
the resistance from IDC to GND. When logic-low, the DC input current limit is internally programmed to
500mA or 100mA, as set by the IUSB logic input. There is an internal diode from DCM (anode) to DC
(cathode) as shown in Figure 1.
5
DCM
6
7
BST
High-Side MOSFET Driver Supply. Bypass BST to LX with a 0.1μF ceramic capacitor.
USB Current-Limit Set Input. Drive IUSB logic-low to set the USB current limit to 100mA. Drive IUSB logic-
high to set the USB current limit to 500mA.
IUSB
DC Power-OK Output. Active-low open-drain output pulls low when a valid input is detected at DC. DOK
is still valid when the charger is disabled (CEN high).
8
9
DOK
VL
Logic LDO Output. VL is the output of an LDO that powers the MAX8903_ internal circuitry and charges
the BST capacitor. Connect a 1μF ceramic capacitor from VL to GND.
Charge Timer Set Input. A capacitor (C ) from CT to GND sets the fast-charge and prequal fault timers.
CT
Connect to GND to disable the timer.
10
CT
DC Current-Limit Set Input. Connect a resistor (R ) from IDC to GND to program the current limit of the
IDC
step-down regulator from 0.5A to 2A when DCM is logic-high.
11
12
IDC
GND
Ground. GND is the low-noise ground connection for the internal circuitry.
______________________________________________________________________________________ 11
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Pin Description (continued)
PIN
NAME
FUNCTION
Charge Current Set Input. A resistor (R
The prequal charge current is 10% of the fast-charge current.
) from ISET to GND programs the fast-charge current up to 2A.
ISET
13
ISET
Charger Enable Input. Connect CEN to GND to enable battery charging when a valid source is connected
at DC or USB. Connect to VL, or drive high to disable battery charging.
14
15
CEN
USB Suspend Input. Drive USUS logic-high to enter USB suspend mode, lowering USB current to 115µA,
and internally shorting SYS to BAT.
USUS
Thermistor Input. Connect a negative temperature coefficient (NTC) thermistor from THM to GND.
Connect a resistor equal to the thermistor +25°C resistance from THM to VL. Charging is suspended
when the thermistor is outside the hot and cold limits. Connect THM to GND to disable the thermistor
temperature sensor.
16
THM
USB Power Input. USB is capable of delivering 100mA or 500mA to SYS as set by the IUSB logic input.
Connect a 4.7µF ceramic capacitor from USB to GND.
17
18
19
USB
FLT
Fault Output. Active-low, open-drain output pulls low when the battery timer expires before prequal or
fast-charge completes.
USB Power-OK Output. Active-low, open-drain output pulls low when a valid input is detected at USB.
UOK is still valid when the charger is disabled (CEN high).
UOK
MX8903A–EGHJN/Y
Battery Connection. Connect to a single-cell Li+ battery. The battery charges from SYS when a valid
source is present at DC or USB. BAT powers SYS when neither DC nor USB power is present, or when the
SYS load exceeds the input current limit. Both BAT pins must be connected together externally.
20, 21
22
BAT
Charger Status Output. Active-low, open-drain output pulls low when the battery is in fast-charge or
prequal. Otherwise, CHG is high impedance.
CHG
System Supply Output. SYS connects to BAT through an internal 50mΩ system load switch when DC or
USB are invalid, or when the SYS load is greater than the input current limit.
When a valid voltage is present at DC or USB, SYS is limited to V . When the system load (I
SYSREG
)
SYS
23, 24
SYS
exceeds the DC or USB current limit, SYS is regulated to 50mV below BAT, and both the powered input
and the battery service SYS.
Bypass SYS to GND with an X5R or X7R ceramic capacitor. See Table 6 for the minimum recommended
SYS capacitor (C
). Both SYS pins must be connected together externally.
SYS
70mΩ Current-Sense Input. Connect the step-down inductor from LX to CS. When the step-down
regulator is on, there is a 70mΩ current-sense MOSFET from CS to SYS. When the step-down regulator is
off, the internal CS MOSFET turns off to block current from SYS back to DC.
25, 26
CS
Inductor Connection. Connect the inductor between LX and CS. Both LX pins must be connected together
externally.
27, 28
—
LX
EP
Exposed Pad. Connect the exposed pad to GND. Connecting the exposed pad does not remove the
requirement for proper ground connections to the appropriate pins.
12 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
PG
LX
BST
CS
MAX8903_
DC POWER
MANAGEMENT
TO
SYSTEM
LOAD
DC
SYS
ISET
AC
ADAPTER
PWR
OK
Li+ BATTERY
CHARGER
AND SYS LOAD SWITCH
PWM
STEP-DOWN
REGULATOR
DOK
CHARGER
CURRENT-
VOLTAGE
CONTROL
BATTERY
CONNECTOR
SET
INPUT
LIMIT
BAT
BAT+
+
BAT-
NTC
USB POWER
MANAGEMENT
USB
UOK
T
USB
THERMISTOR
MONITOR
(SEE FIGURE 7)
THM
VL
PWR
OK
CURRENT-
LIMITED
VOLTAGE
IC
THERMAL
REGULATION
REGULATOR
CHG
CHARGE
TERMINATION
AND MONITOR
SET
INPUT
LIMIT
DC
DCM
IUSB
FLT
CT
DC MODE
500mA
CHARGE
TIMER
INPUT AND
USB
CHARGER
CURRENT-LIMIT
SET LOGIC
LIMIT
100mA
USUS
IDC
USB
SUSPEND
CEN
GND
DC
EP
LIMIT
Figure 1. Functional Block Diagram
______________________________________________________________________________________ 13
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
R
PU
4 x 100kΩ
TO VL
1
PG
2
PG
18
FAULT
OUTPUT
FLT
UOK
DOK
CHG
MAX8903_
C
DC
19
8
4.7μF
USB PWR OK
DC PWR OK
3
DC
DC
ADAPTER
4
6
22
CHARGE
INDICATOR
BST
C
BST
R
R
ISET
27 LX
LX
0.1μF
13
11
ISET
IDC
28
IDC
L1
1μH
25 CS
26 CS
(SEE TABLE 5 FOR
INDUCTOR SELECTION)
SYS 24
TO SYSTEM
LOAD
C
SYS
23
SYS
(SEE TABLE 6 FOR C SELECTION)
SYS
USB
MX8903A–EGHJN/Y
BAT
BAT
21
20
17 USB
VBUS
C
4.7μF
C
10μF
USB
BAT
1-CELL
LI+
GND
5
TO DC
DCM
9
VL
14
OFF
CHARGE ON
C
1μF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15μF
Figure 2. Typical Application Circuit Using a Separate DC and USB Connector
A USB charge input can charge the battery and power
the system from a USB power source. When powered
from USB or the DC input, system load current peaks
that exceed what can be supplied by the input are sup-
plemented by the battery.
Circuit Description
The MAX8903_ is a dual input charger with a 16V input
for a wide range of DC sources and USB inputs. The IC
includes a high-voltage (16V) input DC-DC step-down
converter that reduces charger power dissipation while
also supplying power to the system load. The step-
down converter supplies up to 2A to the system, the
battery, or a combination of both.
The MAX8903_ also manages load switching from the
battery to and from an external power source with an
on-chip 50mΩ MOSFET. This switch also helps support
load peaks using battery power when the input source
is overloaded.
14 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
R
PU
4 x 100kΩ
TO VL
1
2
PG
PG
18
19
8
FAULT
FLT
UOK
DOK
CHG
MAX8903_
OUTPUT
C
DC
4.7μF
USB PWR-OK
DC PWR-OK
3
DC
DC
VBUS
4
6
D-
22
CHARGE
INDICATOR
BST
D+
C
0.1μF
BST
R
R
ISET
27 LX
LX
13
11
ID
ISET
IDC
GND
28
IDC
L1
1μH
25 CS
26 CS
SYS 24
TO SYSTEM
LOAD
(SEE TABLE 6 FOR C SELECTION)
499kΩ
C
SYS
23
SYS
(SEE TABLE 5 FOR
INDUCTOR VALUE
SELECTION)
SYS
BAT
BAT
21
20
17 USB
C
BAT
1-CELL
LI+
USB
ADAPTER
DC MODE
10μF
5
DCM
9
VL
14
OFF
CHARGE ON
C
1μF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15μF
Figure 3. Typical Application Circuit Using a Mini 5 Style Connector or Other DC/USB Common Connector
As shown in Figure 1, the IC includes a full-featured
charger with thermistor monitor, fault timer, charger
status, and fault outputs. Also included are power-OK
signals for both USB and DC. Flexibility is maintained
with adjustable charge current, input current limit, and
a minimum system voltage (when charging is scaled
back to hold the system voltage up).
DC Input—Fast Hysteretic
Step-Down Regulator
If a valid DC input is present, the USB power path is
turned off and power for SYS and battery charging is
supplied by the high-frequency step-down regulator
from DC. If the battery voltage is above the minimum
system voltage (V
, Figure 4), the battery charger
SYSMIN
connects the system voltage to the battery for lowest
power dissipation. The step-down regulation point is
then controlled by three feedback signals: maximum
step-down output current programmed at IDC, maximum
charger current programmed at ISET, and maximum
The MAX8903_ prevents overheating during high ambi-
ent temperatures by limiting charging current when the
die temperature exceeds +100°C.
______________________________________________________________________________________ 15
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Table 1. External Components List for Figures 2 and 3
COMPONENT
FUNCTION
PART
(FIGURES 2 AND 3)
C
, C
Input filter capacitor
VL filter capacitor
4.7µF ceramic capacitor
1.0µF ceramic capacitor
DC USB
C
VL
10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J) or
22µF (MAX8903B/MAX8903E/MAX8903G/MAX8903Y) ceramic capacitor
C
SYS output bypass capacitor
SYS
C
Battery bypass capacitor
Charger timing capacitor
Logic output pullup resistors
Negative TC thermistor
10µF ceramic capacitor
BAT
C
0.15µF low TC ceramic capacitor
CT
R
(X4)
100kΩ
PU
THM
Philips NTC thermistor, P/N 2322-640-63103, 0kΩ 5ꢀ at ꢁ25ꢂC
R
THM pullup resistor
10kΩ
T
DC input current-limit programming
Fast-charge current programming
R
3kΩ 1ꢀ, for 2A limit
1.2kΩ 1ꢀ, for 1A charging
IDC
R
ISET
L1
DC input step-down inductor
1µH inductor with I
> 2A
SAT
die temperature. The feedback signal requiring the
smallest current controls the average output current in
the inductor. This scheme minimizes total power dissi-
pation for battery charging and allows the battery to
absorb any load transients with minimum system volt-
age disturbance.
troller becomes a minimum on-time, valley current regu-
lator. In this way, ripple current in the inductor is always
as small as possible to reduce ripple voltage on SYS for
a given capacitance. The ripple current is made to vary
with input voltage and output voltage in a way that
reduces frequency variation. However, the frequency
still varies somewhat with operating conditions. See the
Typical Operating Characteristics.
MX8903A–EGHJN/Y
If the battery voltage is below V , the charger does
SYSMIN
not directly connect the system voltage to the battery
and the system voltage (V ) is slightly above V
SYS
SYSMIN
DC Mode (DCM)
As shown in Table 2, the DC input supports both AC
adapters (up to 2A) and USB (up to 500mA). With the
DCM logic input set high, the DC input is in adapter
mode and the DC input current limit is set by the resis-
as shown in Figure 4. The battery charger independently
controls the battery charging current. V is set to
SYSMIN
either 3.0V or 3.4V based on the version of MAX8903_.
See Table 6.
After the battery charges to 50mV above V
, the
tance from IDC to GND (R
). Calculate R
accord-
SYSMIN
IDC
IDC
system voltage is connected to the battery. The battery
fast-charge current then controls the step-down con-
verter to set the average inductor current so that both
the programmed input current limit and fast-charge cur-
rent limit are satisfied.
ing to the following equation:
R
= 6000V/I
IDC
DC-MAX
With the DCM logic input set low, the DC input current
limit is internally programmed to 500mA or 100mA as
set by the IUSB logic input. With the IUSB logic input
set high, the DC input current limit is 500mA and the
DC input delivers current to SYS through the step-down
regulator. With the IUSB logic input set low, the DC
input current limit is 100mA. In this 100mA mode, the
step-down regulator is turned off and its high-side
switch operates as a linear regulator with a 100mA cur-
rent limit. The linear regulator’s output is connected to
LX and its output current flows through the inductor into
CS and finally to SYS.
DC-DC Step-Down Control Scheme
A proprietary hysteretic current PWM control scheme
ensures fast switching and physically tiny external com-
ponents. The feedback control signal that requires the
smallest input current controls the center of the peak
and valley currents in the inductor. The ripple current is
internally set to provide 4MHz operation. When the
input voltage decreases near the output voltage, very
high duty cycle occurs and, due to minimum off-time,
4MHz operation is not achievable. The controller then
provides minimum off-time, peak current regulation.
Similarly, when the input voltage is too high to allow
4MHz operation due to the minimum on-time, the con-
The DCM pin has an internal diode to DC as shown in
Figure 1. To prevent current from flowing from DCM
through the internal diode and to the DC input, DCM
cannot be driven to a voltage higher than DC. The
16 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
through the internal diode to DC. This circuit of Figure 3
allows a microprocessor to drive the gate of the MOS-
FET to any state at any time.
when 4.1V < V
< 6.6V. If the USB power-OK output
USB
feature is not required, connect UOK to ground.
Both the UOK and the DOK circuitry remain active in
thermal overload, USB suspend, and when the charger
is disabled. DOK and UOK can also be wire-ORed
together to generate a single power-OK (POK) output.
An alternative to the simple MOSFET and resistor on
DCM as shown in Figure 3 is to place a 1MΩ resistor in
series with the DCM input to the microprocessor. The
microprocessor can then monitor the DOK output and
make sure that whenever DOK is high DCM is also low.
In the event that DCM is driven to a higher voltage than
DC, the 1MΩ series resistance limits the current from
DCM through the internal diode to DC to a few μA.
Thermal Limiting
When the die temperature exceeds +100°C, a thermal
limiting circuit reduces the input current limit by 5%/°C,
bringing the charge current to 0mA at +120°C. Since
the system load gets priority over battery charging, the
battery charge current is reduced to 0mA before the
input limiter drops the load voltage at SYS. To avoid
false charge termination, the charge termination detect
function is disabled in this mode. If the junction temper-
ature rises beyond +120°C, no current is drawn from
USB Input—Linear Regulator
If a valid USB input is present with no valid DC input,
current for SYS and battery charging is supplied by a
low-dropout linear regulator connected from USB to
SYS. The SYS regulation voltage shows the same char-
acteristic as when powering from the DC input (see
Figure 4). The battery charger operates from SYS with
any extra available current, while not exceeding the
maximum-allowed USB current. If both USB and DC
inputs are valid, power is only taken from the DC input.
The maximum USB input current is set by the logic
state of the IUSB input to either 100mA or 500mA.
DC or USB, and V
regulates at 50mV below V
.
SYS
BAT
System Voltage Switching
DC Input
When charging from the DC input, if the battery is
above the minimum system voltage, SYS is connected
to the battery. Current is provided to both SYS and the
battery, up to the maximum program value. The step-
down output current sense and the charger current
sense provide feedback to ensure the current loop
demanding the lower input current is satisfied. The
advantage of this approach when powering from DC is
that power dissipation is dominated by the step-down
regulator efficiency, since there is only a small voltage
drop from SYS to BAT. Also, load transients can be
absorbed by the battery while minimizing the voltage
disturbance on SYS. If both the DC and USB inputs are
valid, the DC input takes priority and delivers the input
current, while the USB input is off.
Power Monitor Outputs (UOK, DOK)
DOK is an open-drain, active-low output that indicates
the DC input power status. With no source at the USB
pin, the source at DC is considered valid and DOK is
driven low when: 4.15V < V
< 16V. When the USB
DC
voltage is also valid, the DC source is considered valid
and DOK is driven low when: 4.45V < V < 16V. The
DC
higher minimum DC voltage with USB present helps
guarantee cleaner transitions between input supplies. If
the DC power-OK output feature is not required, con-
nect DOK to ground.
UOK is an open-drain, active-low output that indicates
the USB input power status. UOK is low when a valid
source is connected at USB. The source at USB is valid
After the battery is done charging, the charger is turned
off and the SYS load current is supplied from the DC
input. The SYS voltage is regulated to V
. The
SYSREG
charger turns on again after the battery drops to the
restart threshold. If the load current exceeds the input
limiter, SYS drops down to the battery voltage and the
50mΩ SYS-to-BAT PMOS switch turns on to supply the
extra load current. The SYS-to-BAT switch turns off again
once the load is below the input current limit. The 50mΩ
PMOS also turns on if valid DC input power is removed.
V
V
SYSREG
BATREG
MAX8903_
V
SYS
I
x R
ON
BAT
V
SYSMIN
USB Input
When charging from the USB input, the DC input step-
down regulator turns off and a linear regulator from
USB to SYS powers the system and charges the bat-
tery. If the battery is greater than the minimum system
voltage, the SYS voltage is connected to the battery.
V
V
= 0V
AND/OR V
CEN
= 5.0V
DC
USB
V
BAT
Figure 4. SYS Tracking V
to the Minimum System Voltage
BAT
______________________________________________________________________________________ 17
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Table 2. Input Limiter Control Logic
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
MAXIMUM
CHARGE
CURRENT**
USB INPUT
CURRENT LIMIT
POWER SOURCE
DOK
UOK DCM*** IUSB USUS
Lesser of
1200V/R
6000V/R
and
AC Adapter at DC Input
L
L
X
X
H
L
X
L
X
L
6000V/R
IDC
ISET
IDC
Lesser of
1200V/R
100mA
and
USB input off. DC
input has priority.
ISET
100mA
USB Power at DC Input
Lesser of
1200V/R
and
L
L
X
X
L
L
L
X
H
X
L
L
H
L
500mA
ISET
500mA
USB suspend
0
Lesser of
H
100mA
500mA
1200V/R
and
ISET
100mA
USB Power at USB Input,
DC Unconnected
Lesser of
1200V/R
ISET
MX8903A–EGHJN/Y
No DC input
H
L
X
H
L
and
500mA
H
H
L
X
X
X
X
H
X
USB suspend
No USB input
0
0
DC and USB Unconnected
H
**Charge current cannot exceed the input current limit. Charge may be less than the maximum charge current if the total SYS load
exceeds the input current limit.
***There is an internal diode from DCM (anode) to DC (cathode) as shown in Figure 1. If the DCM level needs to be set by a μP, use
a MOSFET for isolation as shown in FIgure 3.
X = Don’t care.
The USB input then supplies the SYS load and charges
the battery with any extra available current, while not
exceeding the maximum-allowed USB current. Load
transients can be absorbed by the battery while mini-
mizing the voltage disturbance on SYS. When battery
charging is completed, or the charger is disabled, SYS
circuitry independently manages charging and
adapter/battery power hand-off. In these situations, CEN
may be connected to ground.
Soft-Start
To prevent input transients that can cause instability in
the USB or AC adapter power source, the rate of change
of the input current and charge current is limited. When
an input source is valid, SYS current is ramped from
zero to the set current-limit value in typically 50μs. This
also means that if DC becomes valid after USB, the
SYS current limit is ramped down to zero before switch-
ing from the USB to DC input. At some point, SYS is no
longer able to support the load and may switch over to
is regulated to V
. If both USB and DC inputs are
SYSREG
valid, power is only taken from the DC input.
USB Suspend
Driving USUS high and DCM low turns off charging as
well as the SYS output and reduces input current to
170μA to accommodate USB suspend mode. See
Table 2 for settings.
BAT. The switchover to BAT occurs when V
< V
.
BAT
SYS
Charge Enable (CEN)
When CEN is low, the charger is on. When CEN is high,
the charger turns off. CEN does not affect the SYS out-
put. In many systems, there is no need for the system
controller (typically a microprocessor) to disable the
charger, because the MAX8903_ smart power selector
This threshold is a function of the SYS capacitor size
and SYS load. The SYS current limit then ramps from
zero to the set current level and SYS supports the load
again as long as the SYS load current is less than the
set current limit.
18 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
When the charger is turned on, the charge current ramps
from 0A to the ISET current value in typically 1.0ms.
Charge current also soft-starts when transitioning to fast-
charge from prequal, when the input power source is
switched between USB and DC, and when changing the
USB charge current from 100mA to 500mA with the IUSB
reaches V
and the charge current drops to 10%
BATREG
of the maximum fast-charge current, the charger enters
the DONE state. The charger restarts a fast-charge
cycle if the battery voltage drops by 100mV.
Charge Termination
When the charge current falls to the termination thresh-
logic input. There is no di/dt limiting, however, if R
changed suddenly using a switch.
is
ISET
old (I
) and the charger is in voltage mode, charg-
TERM
ing is complete. Charging continues for a brief 15s
top-off period and then enters the DONE state where
charging stops.
Battery Charger
While a valid input source is present, the battery charg-
er attempts to charge the battery with a fast-charge
current determined by the resistance from ISET to
Note that if charge current falls to I
the input or thermal limiter, the charger does not enter
DONE. For the charger to enter DONE, charge current
must be less than I
age mode, and the input or thermal limiter must not be
reducing charge current.
as a result of
TERM
GND. Calculate the R
following equation:
resistance according to the
ISET
, the charger must be in volt-
TERM
R
ISET
= 1200V/I
CHGMAX
Monitoring Charge Current
The voltage from ISET to GND is a representation of the
battery charge current and can be used to monitor the
current charging the battery. A voltage of 1.5V repre-
sents the maximum fast-charge current.
Charge Status Outputs
Charge Output (CHG)
CHG is an open-drain, active-low output that indicates
charger status. CHG is low when the battery charger is
in its prequalification and fast-charge states. CHG goes
high impedance if the thermistor causes the charger to
go into temperature suspend mode.
If necessary, the charge current is reduced automati-
cally to prevent the SYS voltage from dropping.
Therefore, a battery never charges at a rate beyond the
capabilities of a 100mA or 500mA USB input, or over-
loads an AC adapter. See Figure 5.
When used in conjunction with a microprocessor (μP),
connect a pullup resistor between CHG and the logic
I/O voltage to indicate charge status to the μP.
Alternatively, CHG can sink up to 20mA for an LED
charge indicator.
When V
is below V
, the charger enters pre-
BATPQ
BAT
qual mode and the battery charges at 10% of the maxi-
mum fast-charge rate until the voltage of the deeply
discharged battery recovers. When the battery voltage
Fault Output (FLT)
FLT is an open-drain, active-low output that indicates
charger status. FLT is low when the battery charger has
entered a fault state when the charge timer expires.
This can occur when the charger remains in its prequal
state for more than 33 minutes or if the charger remains
in fast-charge state for more than 660 minutes (see
Figure 6). To exit this fault state, toggle CEN or remove
and reconnect the input source.
MONITORING THE BATTERY
CHARGE CURRENT WITH V
ISET
1.5
ISET
0
V
(V)
When used in conjunction with a microprocessor (μP),
connect a pullup resistor between FLT and the logic I/O
voltage to indicate charge status to the μP.
Alternatively, FLT can sink up to 20mA for an LED fault
indicator. If the FLT output is not required, connect FLT
to ground or leave unconnected.
Charge Timer
A fault timer prevents the battery from charging indefi-
nitely. The fault prequal and fast-charge timers are con-
0
BATTERY CHARGING CURRENT (A)
DISCHARGING
1200V/R
ISET
trolled by the capacitance at CT (C ).
CT
Figure 5. Monitoring the Battery Charge Current with the
Voltage from ISET to GND
______________________________________________________________________________________ 19
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
CEN = HI OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
NOT READY
UOK AND DOK = HIGH IMPEDANCE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ANY STATE
I
= 0mA
CHG
UOK AND/OR DOK = LOW
CEN = 0
RESET TIMER
TOGGLE CEN OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
PREQUALIFICATION
UOK AND/OR DOK = LOW
CHG = LOW
TIMER > t
PREQUAL
FLT = HIGH IMPEDANCE
FAULT
0 < V < V
BAT
BATPQ
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = LOW
I
≤ I
/10
CHG CHGMAX
V
BAT
< V
BATPQ
- 180mV
V
> V
BAT BATPQ
I
= 0mA
CHG
RESET TIMER = 0
RESET TIMER
TIMER > t
FSTCHG
(TIMER SLOWED BY 2x IF
< I /2, AND
FAST-CHARGE
UOK AND/OR DOK = LOW
CHG = LOW
I
CHG CHGMAX
V
< V
- 180mV
RESET TIMER
BAT
BATPQ
PAUSED IF I
< I
/5 WHILE V < V
)
CHG CHGMAX
BAT
BATREG
FLT = HIGH IMPEDANCE
V
< V < V
BAT BATREG
BATPQ
I
≤ I
CHG CHGMAX
I
< I
CHG TERM
MX8903A–EGHJN/Y
AND V = V
BAT
BATREG
I
> I
CHG TERM
AND THERMAL
OR INPUT LIMIT
NOT EXCEEDED;
RESET TIMER
RESET TIMER
ANY CHARGING
STATE
TOP-OFF
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
THM OK
TIMER RESUME
THM NOT OK
TIMER SUSPEND
V
BAT
< V
+ V
BATREG RSTRT
RESET TIMER
V
= V
BATREG
BAT
I
= I
CHG TERM
TEMPERATURE SUSPEND
= 0mA
UOK OR DOK PREVIOUS STATE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
I
CHG
TIMER > t
TOP-OFF
DONE
UOK AND/OR DOK = 0
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
V
+ V < V < V
RSTRT BAT BATREG
BATREG
I
= 0mA
CHG
Figure 6. MAX8903A Charger State Flow Chart
While in fast-charge mode, a large system load or device
self-heating may cause the MAX8903_ to reduce charge
current. Under these circumstances, the fast-charge
timer is slowed by 2x if the charge current drops below
50% of the programmed fast-charge level, and suspend-
ed if the charge current drops below 20% of the pro-
grammed level. The fast-charge timer is not affected at
any current if the charger is regulating the BAT voltage
C
CT
t
= 33min×
PREQUAL
0.15μF
C
0.15μF
CT
t
= 660min×
FST-CHG
t
t
= 15s (MAX8903A/D/H/J/N/Y)
TOP-OFF
TOP-OFF
C
CT
= 132min×
(MAX8903B/E/G)
0.15μF
at V
(i.e., the charger is in voltage mode).
BATREG
20 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
CEN
VL
VL
THERMISTOR
CIRCUITRY
MAX8903_
MAX8903B/MAX8903E/
MAX8903G ONLY
THERMISTOR
DETECTOR
0.87 VL
R
TB
ALTERNATE
THERMISTOR
CONNECTION
0.74 VL
COLD
THM
R
TS
THM
OUT OF
RANGE
0.28 VL
HOT
R
TP
R
T
DISABLE
CHARGER
ENABLE THM
0.03 VL
R
T
ALL COMPARATORS
60mV HYSTERESIS
GND
Figure 7. Thermistor Monitor Circuitry
Thermistor Input (THM)
Table 3. Fault Temperatures for Different
Thermistors
The THM input connects to an external negative tem-
perature coefficient (NTC) thermistor to monitor battery
or system temperature. Charging is suspended when
the thermistor temperature is out of range. The charge
timers are suspended and hold their state but no fault is
indicated. When the thermistor comes back into range,
charging resumes and the charge timer continues from
where it left off. Connecting THM to GND disables the
thermistor monitoring function. Table 3 lists the fault
temperature of different thermistors.
Thermistor β (K)
(kΩ) (Figure 7)
3000 3250 3500 3750 4250
R
10
10
10
10
10
TB
Resistance at +25°C
(kΩ)
10
10
10
10
10
Resistance at +50°C
(kΩ)
4.59
4.30
4.03
3.78 3.316
Resistance at 0°C (kΩ) 25.14 27.15 29.32 31.66 36.91
Since the thermistor monitoring circuit employs an exter-
Nominal Hot Trip
Temperature (°C)
55
-3
53
-1
50
0
49
2
46
nal bias resistor from THM to VL (R , Figure 7), the ther-
TB
mistor is not limited only to 10kΩ (at +25°C). Any
resistance thermistor can be used as long as the value is
equivalent to the thermistor’s +25°C resistance. For
example, with a 10kΩ at +25°C thermistor, use 10kΩ at
Nominal Cold Trip
Temperature (°C)
4.5
VL Regulator
R , and with a 100kΩ at +25°C thermistor, use 100kΩ.
TB
VL is a 5V linear regulator that powers the MAX8903’s
internal circuitry and charges the BST capacitor. VL is
used externally to bias the battery’s thermistor. VL takes
its input power from USB or DC. When input power is
available from both USB and DC, VL takes power from
DC. VL is enabled whenever the input voltage at USB
or DC is greater than ~1.5V. VL does not turn off when
the input voltage is above the overvoltage threshold.
Similarly, VL does not turn off when the charger is dis-
abled (CEN = high). Connect a 1μF ceramic capacitor
from VL to GND.
For a typical 10kΩ (at +25°C) thermistor and a 10kΩ
resistor, the charger enters a temperature suspend
R
TB
state when the thermistor resistance falls below 3.97kΩ
(too hot) or rises above 28.7kΩ (too cold). This corre-
sponds to a 0°C to +50°C range when using a 10kΩ
NTC thermistor with a beta of 3500. The general relation
of thermistor resistance to temperature is defined by
the following equation:
⎧
⎫
1
1
⎛
⎞
β
−
⎨
⎬
⎜
⎝
⎟
⎠
T+273°C
298°C
⎪
⎩
⎪
⎭
R
= R × e
25
T
______________________________________________________________________________________ 21
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
where:
and let the system continue to operate with external power.
If the THM pin is tied to GND (voltage at THM is below 3%
of VL), the thermistor option is disabled and the system
does not respond to the thermistor input. In those cases, it
is assumed that the system has its own temperature sens-
ing, and halts changing through CEN when the tempera-
ture is outside of the safe charging range.
R = The resistance in Ω of the thermistor at tempera-
T
ture T in Celsius
R
25
= The resistance in Ω of the thermistor at +25°C
β = The material constant of the thermistor, which typi-
cally ranges from 3000K to 5000K
T = The temperature of the thermistor in °C
Power Dissipation
Table 3 shows the MAX8903_ THM temperature limits
for different thermistor material constants.
Table 4. Package Thermal Characteristics
Some designs might prefer other thermistor temperature
limits. Threshold adjustment can be accommodated by
28-PIN 4mm x 4mm THIN QFN
SINGLE-LAYER PCB
MULTILAYER PCB
changing R , connecting a resistor in series and/or in
TB
1666.7mW
2286mW
parallel with the thermistor, or using a thermistor with dif-
ferent β. For example, a +45°C hot threshold and 0°C
cold threshold can be realized by using a thermistor
with a β of 4250 and connecting 120kΩ in parallel. Since
the thermistor resistance near 0°C is much higher than it
is near +50°C, a large parallel resistance lowers the
cold threshold, while only slightly lowering the hot
threshold. Conversely, a small series resistance raises
the hot threshold, while only slightly raising the cold
Continuous
Power
Dissipation
Derate 20.8mW/°C
above +70°C
Derate 28.6mW/°C
above +70°C
θ
θ
48°C/W
3°C/W
35°C/W
3°C/W
JA
JC
Minimum SYS Output Capacitor
MX8903A–EGHJN/Y
Based on the version of the MAX8903_, the SYS load
regulation is either 25mV/A or 40mV/A. The 25mV/A ver-
sions achieve better load regulation by increasing the
feedback loop gain. To ensure feedback stability with
this higher gain, a larger SYS output capacitor is
required. Devices with 25m/V SYS load regulation
require 22μF SYS output capacitor whereas devices
with 40m/V only require 10μF. See Table 6 for more
information about the various versions of the
MAX8903_.
threshold. Raising R
lowers both the cold and hot
TB
thresholds, while lowering R raises both thresholds.
TB
Note that since VL is active whenever valid input power
is connected at DC or USB, thermistor bias current
flows at all times, even when charging is disabled (CEN
= high). When using a 10kΩ thermistor and a 10kΩ
pullup to VL, this results in an additional 250μA load.
This load can be reduced to 25μA by instead using a
100kΩ thermistor and 100kΩ pullup resistor.
Power Enable on Battery Detection
The power enabled on battery detection function allows
the MAX8903B/MAX8903E/MAX8903G to automatically
enable/disable the USB and DC power inputs when the
battery is applied/removed. This function utilizes the
battery pack’s integrated thermistor as a sensing mech-
anism to determine when the battery is applied or
removed. With this function, MAX8903B/MAX8903E/
MAX8903G-based systems shut down when the battery
is removed regardless of whether external power is
available at the USB or DC power inputs.
Inductor Selection for
Step-Down DC-DC Regulator
The MAX8903_'s control scheme requires an external
inductor (L
) from 1.0μH to 10μH for proper opera-
OUT
tion. This section describes the control scheme and the
considerations for inductor selection. Table 5 shows
recommended inductors for typical applications. For
assistance with the calculations needed to select the
optimum inductor for a given application, refer to the
spreadsheet at: www.maxim-ic.com/tools/other/soft-
ware/MAX8903-inductor-design.xls.
The MAX8903B/MAX8903E/MAX8903G implement the
power enabled on battery detection function with the ther-
mistor detector comparator as shown in Figure 7. If no bat-
The MAX8903 step-down DC-DC regulator implements a
control scheme that typically results in a constant switch-
ing frequency (f ). When the input voltage decreases to
SW
tery is present, the absence of the thermistor allows R to
TB
a value near the output voltage, high duty cycle operation
pull THM to VL. When the voltage at the THM pin increases
above 87% of VL, it is assumed that the battery has been
removed and the system powers down. However, there is
also the option to bypass this thermistor sensing option
completely, and so retain the ability to remove the battery
occurs and the device can operate at less than f
due
SW
to minimum off-time (t
) constraints. In high duty
OFFMIN
cycle operation, the regulator operates with t
and
OFFMIN
a peak current regulation. Similarly, when the input
voltage is too high to allow f operation due to minimum
SW
22 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
on-time constraints (t
), the regulator becomes a
ONMIN
V
− V
SYS(MIN)
× t
(
)
DC(MAX)
ON
fixed minimum on-time valley current regulator.
(4)
L
=
OUT _MIN_ t
ON
K × I
Versions of the MAX8903 with f = 4MHz offer the
SDLIM
SW
smallest L
while delivering good efficiency with low
OUT
where V
is maximum input voltage, V
the minimum charger output voltage, and t
time at high input voltage, as given by the following
equation:
is
DC(MAX)
SYS(MIN)
is the on-
input voltages (5V or 9V). For applications that use high
ON
input voltages (12V), the MAX8903G with f
is the best choice because of its higher efficiency.
= 1MHz
SW
For a given maximum output voltage, the minimum
inductor ripple current condition occurs at the lowest
⎛
⎞
V
1
f
SW
SYS(MIN)
(5)
t
= t
if
×
≤ t
,
input voltage that allows the regulator to maintain f
SW
⎜
⎟
ON
ONMIN
ONMIN
V
⎝
⎠
DC(MAX)
operation. If the minimum input voltage dictates an off-
time less than t
, then the minimum inductor rip-
OFFMIN
otherwise,
V
1
f
SW
SYS(MIN)
ple condition occurs just before the regulator enters
fixed minimum off-time operation. To allow the current-
mode regulator to provide a low-jitter, stable duty factor
operation, the minimum inductor ripple current
t
=
×
ON
V
DC(MAX)
The saturation current DC rating of the inductor (I
)
SAT
(I
) should be greater than 150mA in the
L_RIPPLE_MIN
must be greater than the DC step-down output current
limit (I ) plus one-half the maximum ripple current,
minimum inductor ripple current condition. The maxi-
mum allowed output inductance L is therefore
SDLIM
OUT_MAX
as given by equation (6).
obtained using the equations (1) and (2) below.
IL
RIPPLE _MAX
2
(1)
I
> I
+
SAT
SDLIM
(6)
⎛
⎞
V
1
f
SW
SYS(MAX)
t
= t
if 1−
×
≤ t
,
⎜
⎟
OFF
OFFMIN
OFFMIN
V
⎝
⎠
DC(MIN)
where IL
is the greater of the ripple currents
RIPPLE_MAX
obtained from (7) and (8).
otherwise,
⎛
⎞
V
1
f
SW
SYS(MAX)
V
× t
OFF
t
= 1−
×
SYS(MAX)
⎜
⎟
OFF
(7)
(8)
IL
=
V
⎝
⎠
RIPPLE _MIN_ T
OFF
DC(MIN)
L
OUT
where t
is the off-time, V
output voltage, and V
age.
is maximum charger
OFF
SYS(MAX)
V
− V
× t
ON
is minimum DC input volt-
(
)
DC(MAX)
SYS(MIN)
DC(MIN)
IL
=
RIPPLE _MIN_ T
ON
L
OUT
V
× t
SYS(MAX)
OFF
L
=
OUT _MAX
PCB Layout and Routing
(2)
I
L _RIPPLE _MIN
Good design minimizes ground bounce and voltage gra-
dients in the ground plane, which can result in instability
or regulation errors. The GND and PGs should connect to
the power-ground plane at only one point to minimize the
effects of power-ground currents. Battery ground should
connect directly to the power-ground plane. The ISET
and IDC current-setting resistors should connect directly
to GND to avoid current errors. Connect GND to the
exposed pad directly under the IC. Use multiple tightly
spaced vias to the ground plane under the exposed pad
to help cool the IC. Position input capacitors from DC,
SYS, BAT, and USB to the power-ground plane as close
as possible to the IC. Keep high current traces such as
those to DC, SYS, and BAT as short and wide as possi-
ble. Refer to the MAX8903A Evaluation Kit for a suitable
PCB layout example.
where L
is the maximum allowed inductance.
OUT_MAX
To obtain a small-sized inductor with acceptable core
loss, while providing stable, jitter-free operation at the
advertised f , the actual output inductance (L
), is
OUT
SW
obtained by choosing an appropriate ripple factor K, and
picking an available inductor in the range inductance
yielded by equations (2), (3), and (4). L
should also
OUT
not be lower than the minimum allowable inductance as
shown in Table 6. The recommended ripple factor ranges
from (0.2 ≤ K 0.45) for (2A ≥ I
≥ 1A) designs.
S
DLIM
(3)
V
× t
SYS(MAX)
OFF
L
=
OUT _MIN_ T
OFF
K × I
SDLIM
where t
is the minimum off-time obtained from (1).
OFF
______________________________________________________________________________________ 23
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MAX8903A–MAX8903E/MAX8903G/MAX8903Y are the
same. Their differences lie in certain electrical and oper-
ational parameters. Table 6 outlines these differences.
Selector Guide
The MAX8903_ is available in several options designat-
ed by the first letter following the root part number. The
basic architecture and functionality of the
Table 5. Recommended Inductor Examples
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
DC INPUT
VOLTAGE
RANGE
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
(I
)
SDMAX
1.0μH, IFSC1008ABER1R0M01, Vishay
2.5mm x 2mm x 1.2mm, 43mΩ (max), 2.6A
or 1.0μH, LQH32PN1R0-NN0, Murata,
3.2mm x 2.5mm x 1.55mm, 54mΩ (max), 2.3A
5V 10%
5V 10%
5V 10%
5V 10%
9V 10%
9V 10%
2A
MAX8903H/J/N/Y, 4MHz
MAX8903H/J/N/Y, 4MHz
1.5μH inductor, MDT2520-CN1R5M, TOKO
2.5mm x 2.0mm x 1.2mm, 123.5mΩ (max), 1.25A
or 1.5uH Inductor, IFSC1008ABER1R5M01, Vishay
2.5mm x 2mm x 1.2mm, 72mΩ (max), 2.2A
1A
2A
1A
2A
1A
MX8903A–EGHJN/Y
2.2μH inductor, DFE322512C-2R2N, TOKO
3.2mm x 2.5mm x 1.2mm, 91mΩ (max), 2.4A
or 2.2μH inductor, IFSC1515AHER2R2M01, Vishay
3.8mm x 3.8mm x 1.8mm, 45mΩ (max), 3A
MAX8903A/B/C/D/E,
4MHz
2.2μH inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2μH Inductor, LQH32PN2R2-NN0, Murata
3.2mm x 2.5mm x 1.55mm, 91mΩ (max), 1.55A
MAX8903A/B/C/D/E,
4MHz
1.5uH inductor, IFSC1008ABER1R5M01, Vishay
2.5mm x 2mm x 1.2mm, 72mW (max), 2.2A
or 1.5μH Inductor, VLS4012ET-1R5N, TDK
4mm x 4mm x 1.2mm, 72mW (max), 2.1A
MAX8903H/J/N/Y, 4MHz
MAX8903H/J/N/Y, 4MHz
2.2μH inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2μH inductor, LQH3NPN2R2NJ0, Murata
3mm x 3mm x 1.1mm, 83mΩ (max), 1.15A
24 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Table 5. Recommended Inductor Examples (continued)
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
DC INPUT
VOLTAGE
RANGE
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
(I
)
SDMAX
2.2μH inductor, DFE322512C-2R2N, TOKO
3.2mm x 2.5mm x 1.2mm, 91mΩ (max), 2.4A
or 2.2μH Inductor, IFSC1515AHER2R2M01, Vishay
3.8mm x 3.8mm x 1.8mm, 45mΩ (max), 3A
MAX8903A/B/C/D/E,
4MHz
9V 10%
9V 10%
9V 10%
9V 10%
12V 10%
12V 10%
2A
2.2μH Inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2μH Inductor, LQH3NPN2R2NJ0, Murata
3mm x 3mm x 1.1mm, 83mΩ (max), 1.15A
MAX8903A/B/C/D/E,
4MHz
1A
2A
1A
2A
1A
4.3uH Inductor, DEM4518C (1235AS-H-4R3M), TOKO
4.7mm x 4.5mm x 1.8mm, 84mΩ (max), 2.0A
or 4.7μH Inductor, IFSC1515AHER4R7M01, Vishay
3.8mm x 3.8mm x 1.8mm, 90mΩ (max), 2.0A
MAX8903G, 1MHz
MAX8903G, 1MHz
MAX8903G, 1MHz
MAX8903G, 1MHz
4.7μH inductor, DEM2818C (1227AS-H-4R7M), TOKO
3.2mm x 2.8mm x 1.8mm, 92mΩ (max), 1.1A
or 4.7μH inductor, IFSC1008ABER4R7M01, Vishay
2.5mm x 2mm x 1.2mm, 212mΩ (max), 1.2A
4.3μH inductor, DEM4518C (1235AS-H-4R3M), TOKO
4.7mm x 4.5mm x 1.8mm, 84mΩ (max), 2.0A
or 4.7μH inductor, IFSC1515AHER4R7M01, Vishay
3.8mm x 3.8mm x 1.8mm, 90mΩ (max), 2.0A
6.8μH, IFSC1515AHER6R8M01, Vishay
3.8mm x 3.8mm x 1.8mm, 115mΩ (max), 1.5A
or 6.8μH, LQH44PN6R8MP0, Murata
4mm x 4mm x 1.65mm, 144mΩ (max), 1.34A
*See the Selector Guide for more information about part numbers.
______________________________________________________________________________________ 25
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MAX8903A–MAX8903E/MAX8903G/MAX8903Y are the
Selector Guide
The MAX8903_ is available in several options designat-
ed by the first letter following the root part number. The
basic architecture and functionality of the
same. Their differences lie in certain electrical and
operational parameters. Table 6 outlines these differ-
ences.
Table 6. Selector Guide
PARAMETER MAX8903A MAX8903B MAX8903C MAX8903D MAX8903E MAX8903G MAX8903H MAX8903J MAX8903N MAX8903Y
Minimum SYS
Regulation
3.0V
3.0V
3.4V
3.4V
3.0V
3.0V
3.4V
3.4V
3.4V
3.0V
Voltage
(V
)
SYSMIN
SYS Regulation
Voltage
4.4V
4.325V
2.2µH
4.4V
4.4V
4.325V
2.2µH
4.325V
2.2µH
4.4V
1µH
4.5V
1µH
4.4V
1µH
4.4V
1µH
(V
SYSREG
)
Minimum
Allowable
Inductor
2.2µH
2.2µH
2.2µH
Switching
Frequency
4MHz
4MHz
4MHz
4MHz
4MHz
1MHz
4MHz
4MHz
4MHz
4MHz
MX8903A–EGHJN/Y
SYS Load
Regulation
40mV/A
25mV/A
40mV/A
40mV/A
25mV/A
25mV/A
40mV/A
25mV/A
25mV/A
25mV/A
Minimum SYS
Output
10µF
4.2V
22µF
4.2V
10µF
4.2V
10µF
4.1V
22µF
4.1V
22µF
4.2V
10µF
4.2V
10µF
22µF
22µF
Capacitor (C
)
SYS
BAT Regulation
Voltage
4.35V
4.15V
4.15V
(V
BATREG
)
(Note 5)
BAT Prequal
Threshold
3V
2.5V
3V
3V
2.5V
2.5V
3V
3V
3V
3V
(V
BATPQ
)
(Note 5)
Top-Off Timer
(Note 6)
15s (fixed)
1mA
132min
10mA
15s (fixed) 15s (fixed)
132min
10mA
132min
10mA
15s (fixed) 15s (fixed) 15s (fixed) 15s (fixed)
VL Output
Current Rating
1mA
1mA
1mA
1mA
1mA
1mA
Power-Enable
On Battery
Detection
No
—
Yes
—
No
—
No
—
Yes
—
Yes
—
No
No
—
No
—
No
—
(Note 7)
Comments
(Note 8)
Note 5: Typical values. See the Electrical Characteristics table for min/max values.
Note 6: Note that this also changes the timing for the prequal and fast-charge timers.
Note 7: See the Power Enable on Battery Detection section for details.
Note 8: The MAX8903H is a newer version of the MAX8903C that is a recommended for new designs.
26 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
21 20 19 18 17 16 15
14
13
22
CEN
ISET
CHG
SYS 23
12 GND
24
25
26
27
28
SYS
CS
CS
LX
MAX8903_
IDC
CT
11
10
9
VL
EP
8
DOK
LX
+
1
2
3
4
5
6
7
TQFN
______________________________________________________________________________________ 27
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
LAND
PATTERN NO.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
21-0139
90-0035
28 TQFN-EP
T2844-1
MX8903A–EGHJN/Y
28 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
MX8903A–EGHJN/Y
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
______________________________________________________________________________________ 29
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
2
3
4
5
12/08
8/09
Initial release
—
1–20
Added MAX8903C/MAX8903D to data sheet
Made various corrections
11/09
10/10
5/11
1–7, 9, 11–21
1–29
Added MAX8903B, MAX8903E, MAX8903G, and MAX8903Y
Added MAX8903H and MAX8903J and updated components
1–29
9/11
Added the MAX8903N, and removed future product designation for MAX8903J
1–29
MX8903A–EGHJN/Y
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
30 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
19-4413; Rev 2; 10/10
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
General Description
Features
The MAX8903A evaluation kit (EV kit) is a fully assem-
bled and tested circuit board for evaluating the 2A, 1-cell
Li+ DC-DC battery charger. The EV kit charges a sin-
gle-cell lithium-ion (Li+) battery from a DC input (AC
adaptor) or a USB 100mA/500mA source and provides
system power from the DC input, USB input, or battery.
Battery charge current and SYS current limit are inde-
pendently set. Charge current and DC converter output
current limit can be set up to 2A, respectively. The USB
input current can be set to 100mA or 500mA and USB
suspend mode is also supported. Power not used by
the system is available to charge the battery.
♦ DC-DC Converter Output Current-Limit
Adjustment Range of 0.5A to 2A (EV Kit Standard
Configuration: 2A)
♦ Battery Charger Current-Limit Adjustment Range
of 0.5A to 2A (EV Kit Standard Configuration: 1A)
♦ USB Current Limit of 100mA or 500mA
♦ Efficient 4MHz Switching DC-DC Converter
Powers System Load and Charger
♦ Instant On—Works with No Battery or Low
Battery
The EV kit comes standard with the MAX8903A
installed. However, the EV kit can also be used to evalu-
ate the MAX8903B–MAX8903E and MAX8903Y by
replacing the MAX8903A (U1) with the preferred IC.
♦ 28-Pin, 4mm x 4mm Thin QFN Package with
Exposed Pad
♦ Fully Assembled and Tested
Ordering Information
PART
TYPE
MAX8903AEVKIT+
EV Kit
+Denotes lead(Pb)-free and RoHS compliant
Component List
DESIGNATION QTY
DESCRIPTION
2.2μF 10%, 16V X5R ceramic
capacitor (0805)
TDK C2012X7R1C225K or
equivalent
C1
C2
1
1
2
2
1
4.7μF 10%, 25V X5R ceramic
capacitor (0805)
Murata GRM21BR61E475KA12L or
equivalent
10μF 10%, 10V X5R ceramic
capacitors (0805)
Taiyo Yuden LMK212BJ106KG or
equivalent
C3A, C4
C5, C7
C6
0.1μF 10%, 10V X7R ceramic
capacitors (0402)
TDK C1005X5R1A104K or
equivalent
2.2μF 10%, 6.3V X5R ceramic
capacitor (0603)
Taiyo Yuden LMK107BJ225MA or
equivalent
Figure 1. MAX8903A EV Kit Photo
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX8903A Evaluation Kit
Component List (continued)
DESIGNATION QTY
DESCRIPTION
DESIGNATION QTY
DESCRIPTION
C8, C9, C11
0
Not installed, capacitors (0402)
1μH, 2.8A, 54mΩ inductor
(4.1mm x 4.1mm x 1.2mm)
TOKO A1101AS-1R0 (DEA4012CK
series)
4.7μF 10%, 16V X5R ceramic
capacitor (0805)
Taiyo Yuden EMK212BJ475K or
equivalent
L1
1
C10
1
100kΩ NTC thermistor (0402)
Murata NCP15WF104J03RC
NTC
0
Small green LEDs
Panasonic LNJ308G8PRA
D1, D3, D4
D2
3
1
2
1
R1–R4
R5
4
1
2.2kΩ 5% resistors (0402)
100kΩ 1% resistor (0402)
Small red LED
Panasonic LNJ208R8ARA
R6, R10, R14,
R17, R18
0
Not installed, resistors (0402)
USB type-AB right-angle mini jacks
Molex 56579-0576
J1, J2
J3
R7, R8
R9
2
1
2
1
3.01kΩ 1% resistors (0402)
6.04kΩ 1% resistor (0402)
604Ω 1% resistors (0402)
1.21kΩ 1% resistor (0402)
2.1mm male power connector
CUI Inc. PJ-002A-SMT
R11, R12
R13
1.25mm (0.049in) surface-mount,
right-angle pitch header, lead-free,
10 circuits
0.56Ω 1% resistor (0603)
Panasonic ERJ-3RQJR56V
J4
1
R15
U1
—
1
1
Molex 53261-1071
1-cell Li+ charger (28 TQFN-EP*)
Maxim MAX8903AETI+
3-pin headers
Sullins PEC36SAAN
Digi-Key S1012E-36-ND
JU1, JU2, JU3,
JU8, JU9
5
6
Shunts (see Table 1)
Digi-Key S900-ND or equivalent
10
1
2-pin headers
Sullins PEC36SAAN
Digi-Key S1012E-36-ND
JU4–JU7,
JU10, JU11
—
PCB: MAX8903A EVALUATION KIT+
*EP = Exposed pad.
Component Suppliers
SUPPLIER
PHONE
WEBSITE
CUI Inc.
503-612-2300
800-344-4539
800-768-6539
770-436-1300
800-344-2112
760-744-0125
800-348-2496
847-803-6100
847-297-0070
www.cui.com
Digi-Key Corp.
Molex
www.digikey.com
www.molex.com
Murata Electronics North America, Inc.
Panasonic Corp.
www.murata-northamerica.com
www.panasonic.com
www.sullinselectronics.com
www.t-yuden.com
Sullins Electronics Corp.
Taiyo Yuden
TDK Corp.
www.component.tdk.com
www.tokoam.com
vluates:–E/MAX8903Y
TOKO America, Inc.
Note: Indicate that you are using the MAX8903 when contacting these component suppliers.
2
_______________________________________________________________________________________
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
7) Remove the shunt from pins 1-2 of jumper JU8 and
Quick Start
Recommended Equipment
place the shunt on pins 2-3 of jumper JU8.
8) If 3V ≤ V
≤ 4.1V for MAX8903A/MAX8903B/
BAT
• MAX8903A EV kit
MAX8903C, or 3V ≤ V
≤ 4.0V for MAX8903D/
BAT
• Adjustable DC power supply capable of greater than
6V at 3A
MAX8903E/MAX8903Y, verify that the current
from BATT into the battery is approximately 1A.
• Battery or simulated battery
9) Increase the load current on SYS to 1A.
1-cell Li+ or Li-poly battery (Figure 2A)
10) Verify that the voltage on SYS remains approximate-
ly equal to V
.
BATT
Simulated battery—preloaded power supply
(Figure 2B)
11) Verify that the charge current into the battery
remains near 1A.
• Two digital multimeters (DMM)
• Up to 3A adjustable load
• Three 10A ammeters
12) Increase the load current on SYS to 1.5A.
13) Verify that the voltage on SYS remains approximate-
ly equal to V
.
BATT
Procedure
The EV kit is fully assembled and tested. Follow the
steps below to verify board operation. Use twisted
wires of appropriate gauge that are as short as possi-
ble to connect the battery and power sources.
14) Verify that the charge current into the battery
decreased to approximately 0.5A.
15) Increase the load current on SYS to 2.5A.
16) Verify that current out of the battery (from the bat-
tery to SYS) is near 0.5A.
1) Preset the DC power supply to 6V. Turn off the
power supply. Caution: Do not turn on the power
supply until all connections are completed.
Detailed Description of Hardware
Adjusting the EV Kit for In-Circuit
Evaluation
2) Preset the adjustable load to 0A.
3) Connect the EV kit to the power supply, battery or
preloaded power supply, adjustable load, and
meters, as shown in Figure 3.
Verify that the AC adapter source current limit is higher
than the SYS and BAT current requirements. Note that if
SYS current demand exceeds the DC-DC converter
output current limit, then the battery will help supply the
extra current. The DC-DC converter output current limit
can also be adjusted on the MAX8903A EV kit by
replacing R7 or adjusting JU4 and JU5. Verify that the
USB source supplies at least 500mA. Verify the maxi-
mum charge current rating or desired charge current
4) Ensure that the EV kit has the jumper settings
shown in Figure 3 and Table 1.
5) Turn on the power supply.
6) Verify that the voltage at SYS is approximately 4.4V
and that the current from BATT into the battery is 0A.
A. Li+\Li-POLY BATTERY
BAT
B. SIMULATED BATTERY (PRELOADED POWER SUPPLY)
BAT
0 TO 4.2V
≥ 2.5A
2Ω
≥ 10W
MAX8903A EV KIT
MAX8903A EV KIT
GND
GND
Figure 2. Battery Options for Evaluating the MAX8903A EV Kit
_______________________________________________________________________________________
3
MAX8903A Evaluation Kit
JU11
SYS
A
A
SYS
VOLTMETER
ADJUSTABLE
LOAD
MAX8903A
EVALUATION KIT
1
2
3
A
DC
JU1
GND
BAT
POWER
SUPPLY
GND
BAT
BATTERY OR
VOLTMETER
SIMULATED BATTERY
1
2
3
1
2
3
GND
*ALL AMMETERS NEED TO BE SET FOR 10A READINGS. THIS MINIMIZES THE SERIES IMPEDANCE OF THE AMMETER.
Figure 3. Connection Diagram and Default Jumper Connections
Table 1. Jumper Settings (JU1–JU11)
DESCRIPTION
DEFAULT
POSITION
JUMPER
JU1
LABEL
—
PINS 1-2
PINS 2-3
Pins 2-3 shunted
Use the DC pad or J2 as the DC input
Use the DC pad or J3 as the DC input
Configures DC input as adapter source
(see Table 2)
Configures DC input for USB power
(see Table 2)
JU2
DCM
Pins 1-2 shunted
With DCM pins 1-2 shunted, IUSB sets
500mA USB charge current
With DCM pins 2-3 shunted, IUSB sets
100mA USB charge current
JU3
IUSB
Pins 1-2 shunted
JU4
JU5
JU6
JU7
—
—
—
—
Shunted
Shunted
Open
Shorts out R8 (see Table 3)
Shorts out R9 (see Table 3)
Shunting JU6 shorts out R12 (see Table 4)
Shorts out R13 (see Table 4)
Shunted
Disables the battery charger
(when the charger is off, SYS remains on)
Enables the battery charger
(when the charger is on, SYS remains on)
JU8
CEN
Pins 1-2 shunted
JU9
JU10
JU11
USUS
THM
—
Pins 2-3
Shunted
Shunted
USB suspend mode
USB not suspended
Connects THM to GND to bypass thermistor function
Indicator LED anodes connected to SYS
vluates:–E/MAX8903Y
4
_______________________________________________________________________________________
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
rating of the battery. Ensure that the charge current set-
ting of the EV kit does not exceed the battery rating, or
replace resistor R11 (or adjust JU6 and JU7) as
required. See the Adjusting the DC-DC Converter
Output Current Limit and BAT Fast-Charge Current
Limit section for more details.
3) When charging the battery with V
> V
,
SYSMIN
BAT
the SYS voltage is regulated at the battery voltage
for lowest power dissipation.
When the input current limit is reached, the first action
taken by the MAX8903 is to reduce battery charge cur-
rent. This allows the charging current to be pro-
grammed for the fastest charge time, without dropping
the SYS load at load currents that would cause the
input supply regulation current to be exceeded.
Adjusting the DC-DC Converter Output
Current Limit and BAT Fast-Charge
Current Limit
If, after the charge current is reduced to 0mA, the load
at SYS still exceeds the input current limit, the battery
helps supply power to support the system load.
Input and charger current limits are set, as shown in
Table 2. It is often preferable to change the input cur-
rent limit as the input power source is changed. The
MAX8903A facilitates this by allowing different input
current limits for the DC and USB inputs.
The MAX8903 features flexible input connections (at the
DC and USB inputs) and current-limit settings (set by
DCM and IUSB) to accommodate nearly any input power
configuration. However, it is expected that most systems
use one of two external power schemes: separate con-
nections for USB and an AC adapter, or a single connec-
tor that accepts either USB or the AC adapter output.
Input and charger current limits are shown in Table 2.
The SYS voltage regulates to three different regulation
points depending on the state of the MAX8903:
1) If CEN is high to disable the charger, or charging is
done, the SYS voltage regulates to 4.4V.
2) When charging the battery with V
< V
, the
BAT
SYSMIN
SYS voltage regulates to V
+ 0.2V and stays
SYSMIN
above V
during transient loads.
SYSMIN
Table 2. Input Limiter Control Logic
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
MAXIMUM
CHARGE
CURRENT***
USB INPUT
CURRENT LIMIT
POWER SOURCE
DOK
UOK
DCM
IUSB USUS
Lesser of
AC Adapter at DC Input
L
L
X
H
L
X
L
X
L
6000/R
1200/R
and
ISET
IDC
6000/R
IDC
Lesser of
USB input off. DC 1200/R and
X
100mA
ISET
input has priority.
100mA
USB Power at DC Input
Lesser of
L
L
X
X
L
L
L
X
H
X
L
L
H
L
500mA
1200/R
and
ISET
500mA
USB suspend
0
Lesser of
1200/R
H
100mA
500mA
and
ISET
100mA
USB Power at USB Input,
DC Unconnected
Lesser of
1200/R
No DC input
H
L
X
H
L
and
ISET
500mA
H
H
L
X
X
X
X
H
X
USB suspend
No USB input
0
0
DC and USB Unconnected
H
***Charge current cannot exceed the input current limit. Charge may be less than the maximum charge current if the total SYS load
exceeds the input current limit.
X = Don’t care.
_______________________________________________________________________________________
5
MAX8903A Evaluation Kit
EV Kit On-Board Current-Limit Adjustment
The MAX8903’s DC-DC converter output current limit
can be adjusted on the EV kit by shunting JU4, JU5, or
both. See Table 3 for jumper and resistor combinations
and corresponding current limits. The BAT fast-charge
current limit can be adjusted by shunting JU6, JU7, or
both. See Table 4 for jumper and resistor combinations
and corresponding fast-charge current limits.
While in fast-charge mode, a large system load or device
self-heating could cause the MAX8903 to reduce charge
current. Under these circumstances, the fast-charge
timer is slowed by 2x if the charge current drops below
50% of the programmed fast-charge level, and suspend-
ed if the charge current drops below 20% of the pro-
grammed level. The fast-charge timer is not affected at
any current if the charger is regulating the BAT voltage at
4.2V (i.e., the charger is in voltage mode).
Thermistor (THM)
The EV kit comes with a thermistor preinstalled on the
NTC footprint. To evaluate the MAX8903A with a bat-
tery-pack thermistor, remove the thermistor and connect
to the EV kit using the THM pad. Details of thermistors
are covered in the MAX8903 IC data sheet. To disable
the thermistor function, shunt jumper JU10.
Indicator LEDs
Indicator LEDs are provided for CHG, FLT, DOK, and
UOK. The CHG LED (D3) is on when the battery charg-
er is in its prequalification and fast-charge states. The
FLT LED (D2) is on when the battery charger has
entered a fault state after the charge timer expires. The
DOK LED (D1) is on when 4.15V < V
< 16V. The
DC
Charge Timers
A fault timer prevents the battery from charging indefi-
nitely. The fault prequalification and fast-charge timers
are controlled by the capacitance at CT (C5).
UOK LED (D4) is on when the source at USB is 4.1V <
V
< 6.6V. Refer to the MAX8903 IC data sheet for
USB
more details regarding CHG, FLT, DOK, and UOK.
Charge Enable (CEN)
When CEN is low, the charger is on. When CEN is high,
the charger turns off. CEN does not affect the SYS out-
put, which remains on. In many systems, there is no
need for the system controller (typically a microproces-
sor) to disable the charger, because the MAX8903
Smart Power Selector™ circuitry independently man-
ages charging and adapter/battery power hand-off. In
these situations, CEN may be connected to ground.
C5
0.15μF
t
= 33min ×
PREQUAL
(t
is when V
< 3V).
PREQUAL
BATT
C5
0.15μF
t
= 660min ×
FST-CHG
t
t
= 15s(MAX8903A/C/ D/Y)
TOP-OFF
TOP-OFF
C
CT
= 132min ×
(MAX8903B/E)
0.15μF
Table 3. DC-DC Converter Output Current Limit (JU4, JU5)
JUMPER
RESISTORS FROM IDC TO
GND
RESISTANCE FROM IDC TO
SYS CURRENT LIMIT (A)
GND (ꢀ)
JU4
JU5
Open
Open
Shunt
Shunt
Open
Shunt
Open
Shunt
R7 + R8 + R9
R7 + R8
R7 + R9
R7
12k
6k
0.5
1
9k
0.66
2
3k
vluates:–E/MAX8903Y
Table 4. BAT Fast-Charge Current Limit (JU6, JU7)
JUMPER
RESISTORS FROM IDC TO
GND
RESISTANCE FROM IDC TO
BAT FAST-CHARGE CURRENT
LIMIT (A)
GND (ꢀ)
JU6
JU7
Open
Open
Shunt
Shunt
Open
Shunt
Open
Shunt
R11 + R12 + R13
R11 + R12
R11 + R13
R11
2.4k
1.2k
1.8k
604
0.5
1
0.66
2
Smart Power Selector is a trademark of Maxim Integrated Products, Inc.
_______________________________________________________________________________________
6
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
DC
DC
3
4
28
LX
1
1
2
3
DC
DC
JU1
27
LX
2
3
4
5
C10
4.7μF
J2
L1
C1
2.2μF
1μH
R15
0.56Ω
1%
LED
26
25
CS
CS
GND
1
2
PG
PG
JU11
DC
1
3
2
SYS
24
23
SYS
SYS
J3
TP3
1
2
3
C4
10μF
JU2
5
GND
DCM
C7
0.1μF
LX
VL
U1
CHG
6
7
BST
1
2
3
MAX8903A
JU3
R3
2.2kΩ
1%
IUSB
LED
R1
2.2kΩ
LED
22
1%
CHG
D3
8
BATT
GND
DOK
DOK
21
20
D1
J4
BAT
BAT
VL
J4-10
J4-9
J4-8
J4-7
J4-6
J4-5
J4-4
J4-3
J4-2
J4-1
C3A
10μF
9
VL
CT
C5
0.1μF
C6
2.2μF
THM
10
UOK
C8
OPEN
R10
OPEN
TP1
R4
2.2kΩ
1%
LED
R17
OPEN
19
UOK
D4
D2
R7
3.01kΩ
1%
FLT
JU5
JU4
11
12
R2
2.2kΩ
1%
IDC
LED
R9
6.04kΩ
1%
R8
3.01kΩ
GND
18
17
FLT
1%
C9
R14
OPEN
TP2
1
2
3
4
OPEN
USB
GND
R18
OPEN
USB
J1
C2
4.7μF
R11
604Ω
1%
JU7
JU6
VL
13
ISET
R13
1.21kΩ
1%
R12
604Ω
1%
VL
R5
100kΩ
1%
THM
THM
1
2
3
JU8
14
15
16
CEN
THM
VL
R6
OPEN
JU10
C11
OPEN
1
2
3
NTC
JU9
USUS
EP
Figure 4. MAX8903A EV Kit Schematic
_______________________________________________________________________________________
7
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
Figure 5. MAX8903A EV Kit Component Placement Guide—Top Layer
8
_______________________________________________________________________________________
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
Figure 6. MAX8903A EV Kit PCB Layout—Top Layer
_______________________________________________________________________________________
9
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
Figure 7. MAX8903A EV Kit PCB Layout—Inner Layer 2
10 ______________________________________________________________________________________
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
Figure 8. MAX8903A EV Kit PCB Layout—Inner Layer 3
______________________________________________________________________________________ 11
MAX8903A Evaluation Kit
Figure 9. MAX8903A EV Kit PCB Layout—Bottom Layer
vluates:–E/MAX8903Y
12 ______________________________________________________________________________________
MAX8903A Evaluation Kit
vluates:–E/MAX8903Y
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
1
2
1/09
8/09
Initial release
—
Added MAX8903C and MAX8903D to parts evaluated
1–12
1–12
10/10
Added MAX8903B, MAX8903E, and MAX8903Y to parts evaluated
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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