MAX1908|MAX8724 [MAXIM]
Low-Cost Multichemistry Battery Chargers ; 低成本，多种电池充电器\n
| 型号： | MAX1908|MAX8724 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Low-Cost Multichemistry Battery Chargers
|
| 文件： | 总27页 (文件大小：604K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-2764; Rev 1; 1/04
Low-Cost Multichemistry Battery Chargers
General Description
Features
The MAX1908/MAX8724 highly integrated, multichemistry
battery-charger control ICs simplify the construction of
accurate and efficient chargers. These devices use ana-
log inputs to control charge current and voltage, and can
be programmed by the host or hardwired. The MAX1908/
MAX8724 achieve high efficiency using a buck topology
with synchronous rectification.
♦ ±0.5% Output Voltage Accuracy Using Internal
Reference (0°C to +85°C)
♦ ±4% Accurate Input Current Limiting
♦ ±5% Accurate Charge Current
♦ Analog Inputs Control Charge Current and
Charge Voltage
The MAX1908/MAX8724 feature input current limiting.
This feature reduces battery charge current when the
input current limit is reached to avoid overloading the AC
adapter when supplying the load and the battery charger
simultaneously. The MAX1908/MAX8724 provide outputs
to monitor current drawn from the AC adapter (DC input
source), battery-charging current, and the presence of
an AC adapter. The MAX1908’s conditioning charge fea-
ture provides 300mA to safely charge deeply discharged
lithium-ion (Li+) battery packs.
♦ Outputs for Monitoring
Current Drawn from AC Adapter
Charging Current
AC Adapter Presence
♦ Up to 17.6V Battery-Voltage Set Point
♦ Maximum 28V Input Voltage
♦ >95% Efficiency
The MAX1908 includes a conditioning charge feature
while the MAX8724 does not.
♦ Shutdown Control Input
♦ Charges Any Battery Chemistry
The MAX1908/MAX8724 charge two to four series Li+
cells, providing more than 5A, and are available in a
space-saving 28-pin thin QFN package (5mm × 5mm).
An evaluation kit is available to speed designs.
Li+, NiCd, NiMH, Lead Acid, etc.
Applications
Ordering Information
Notebook and Subnotebook Computers
PART
MAX1908ETI
MAX8724ETI
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN
28 Thin QFN
Personal Digital Assistants
Hand-Held Terminals
Minimum Operating Circuit
AC ADAPTER
INPUT
TO EXTERNAL
LOAD
0.01Ω
Pin Configuration
CSSP
DCIN
CSSN
CELLS
TOP VIEW
LDO
REFIN
VCTL
ICTL
ACIN
ACOK
SHDN
ICHG
IINP
28 27 26 25 24 23 22
BST
LDO
DLOV
DCIN
LDO
CLS
REF
1
2
3
4
5
6
7
21 DLO
20 PGND
19 CSIP
18 CSIN
17 CELLS
16 BATT
15 VCTL
MAX1908
MAX8724
DHI
LX
FROM HOST µP
MAX1908
MAX8724
DLO
PGND
10µH
CCS
CCI
CSIP
CCV
CCV
CCI
0.015Ω
CSIN
BATT
CCS
BATT+
8
9
10 11 12 13 14
REF
CLS
GND
THIN QFN
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Low-Cost Multichemistry Battery Chargers
ABSOLUTE MAXIMUM RATINGS
DCIN, CSSP, CSSN, ACOK to GND.......................-0.3V to +30V
BST to GND............................................................-0.3V to +36V
BST to LX..................................................................-0.3V to +6V
LDO, SHDN to GND .................................................-0.3V to +6V
DLOV to LDO.........................................................-0.3V to +0.3V
DLO to PGND .........................................-0.3V to (V
+ 0.3V)
DLOV
DHI to LX...................................................-0.3V to (V
+ 0.3V)
LDO Short-Circuit Current...................................................50mA
BST
LX to GND .................................................................-6V to +30V
BATT, CSIP, CSIN to GND .....................................-0.3V to +20V
CSIP to CSIN or CSSP to CSSN or PGND
to GND...............................................................-0.3V to +0.3V
CCI, CCS, CCV, DLO, ICHG,
Continuous Power Dissipation (T = +70°C)
A
28-Pin Thin QFN (5mm × 5mm)
(derate 20.8mW/°C above +70°C) .........................1666.7mW
Operating Temperature Range ..........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-60°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
IINP, ACIN, REF to GND...........................-0.3V to (V
DLOV, VCTL, ICTL, REFIN, CELLS, CLS,
+ 0.3V)
LDO
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
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = float, CLS =
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REFIN
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE VOLTAGE REGULATION
V
V
V
V
= V
= V
= V
(2, 3, or 4 cells)
-0.5
-0.5
-0.5
4.0
+0.5
+0.5
+0.5
4.2
VCTL
VCTL
VCTL
VCTL
REFIN
Battery Regulation Voltage
Accuracy
/ 20 (2, 3, or 4 cells)
%
REFIN
(2, 3, or 4 cells)
LDO
VCTL Default Threshold
REFIN Range
rising
4.1
V
V
V
(Note 1)
2.5
3.6
REFIN Undervoltage Lockout
V
falling
1.20
1.92
REFIN
CHARGE CURRENT REGULATION
CSIP-to-CSIN Full-Scale Current-
Sense Voltage
V
= V
71.25
75
78.75
mV
%
ICTL
REFIN
V
V
V
V
= V
= V
= V
-5
-5
+5
+5
+6
4.2
ICTL
ICTL
ICTL
ICTL
REFIN
REFIN
LDO
Charging Current Accuracy
ICTL Default Threshold
x 0.6
-6
rising
4.0
4.1
V
V
BATT/CSIP/CSIN Input Voltage
Range
0
19
V
= 0 or V
= 0 or SHDN = 0
ICTL
1
DCIN
CSIP/CSIN Input Current
µA
A
Charging
400
6.8
650
Cycle-by-Cycle Maximum Current
Limit
I
RS2 = 0.015Ω
6.0
7.5
MAX
ICTL Power-Down Mode
Threshold Voltage
REFIN / REFIN / REFIN /
V
rising
V
ICTL
100
55
33
+1
+1
V
V
= V
= 0 or 3V
-1
VCTL
DCIN
ICTL
ICTL, VCTL Input Bias Current
µA
= 0, V
= V
= V = 5V
REFIN
-1
VCTL
ICTL
2
_______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = float, CLS =
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REFIN
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
A
PARAMETER
SYMBOL
CONDITIONS
= 3V
REFIN
MIN
-1
TYP
MAX
+1
UNITS
µA
V
V
V
V
V
V
V
V
= 5V, V
= 5V
DCIN
REFIN Input Bias Current
ICHG Transconductance
-1
+1
REFIN
G
- V
CSIN
- V
CSIN
- V
CSIN
- V
CSIN
- V
CSIN
- V
CSIN
= 45mV
= 75mV
= 45mV
= 5mV
2.7
-6
3
3.3
+6
µA/mV
ICHG
CSIP
CSIP
CSIP
CSIP
CSIP
CSIP
ICHG Accuracy
-5
+5
%
-40
350
3.5
+40
ICHG Output Current
= 150mV, V
= 0
µA
V
ICHG
ICHG Output Voltage
= 150mV, ICHG = float
INPUT CURRENT REGULATION
CSSP-to-CSSN Full-Scale
Current-Sense Voltage
72
75
78
mV
%
V
V
= V
= V
-4
+4
CLS
CLS
REF
Input Current-Limit Accuracy
/ 2
-7.5
+7.5
REF
CSSP, CSSN Input Voltage
Range
8
28
V
V
V
= 0
0.1
1
DCIN
CSSP
CSSP, CSSN Input Current
µA
= V
= V
> 8V
DCIN
350
600
REF
+1
CSSN
CLS Input Range
1.6
-1
V
CLS Input Bias Current
IINP Transconductance
V
V
V
V
V
V
= 2V
µA
CLS
G
- V
CSSN
- V
CSSN
- V
CSSN
- V
CSSN
- V
CSSN
= 75mV
= 75mV
= 37.5mV
2.7
-5
3
3.3
+5
µA/mV
IINP
CSSP
CSSP
CSSP
CSSP
CSSP
IINP Accuracy
%
-7.5
350
3.5
+7.5
IINP Output Current
= 150mV, V
= 0
µA
V
IINP
IINP Output Voltage
= 150mV,V
= float
IINP
SUPPLY AND LDO REGULATOR
DCIN Input Voltage Range
V
8
7
28
V
V
DCIN
V
V
falling
rising
7.4
7.5
3.2
DCIN
DCIN
DCIN Undervoltage-Lockout Trip
Point
7.85
6
DCIN Quiescent Current
I
I
8.0V < V
< 28V
DCIN
mA
µA
DCIN
V
V
= 19V, V
= 0
1
BATT
BATT
DCIN
BATT Input Current
BATT
= 2V to 19V, V
= 19.3V
200
5.4
34
500
5.55
100
DCIN
LDO Output Voltage
LDO Load Regulation
8V < V
< 28V, no load
5.25
3.20
V
DCIN
0 < I
< 10mA
mV
LDO
LDO Undervoltage-Lockout Trip
Point
V
= 8V
4
5.15
V
V
DCIN
REFERENCE
REF Output Voltage
0 < I
< 500µA
4.072
4.096
4.120
REF
_______________________________________________________________________________________
3
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = float, CLS =
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REFIN
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
REF Undervoltage-Lockout Trip
Point
V
V
falling
3.1
3.9
V
REF
TRIP POINTS
BATT Power-Fail Threshold
falling, referred to V
50
100
200
150
mV
mV
DCIN
CSIN
BATT Power-Fail Threshold
Hysteresis
ACIN Threshold
ACIN rising
0.5% of REF
2.007
-1
2.048
20
2.089
+1
V
ACIN Threshold Hysteresis
ACIN Input Bias Current
SWITCHING REGULATOR
mV
µA
V
= 2.048V
ACIN
V
V
= 16V, V
= 19V,
BATT
DCIN
DHI Off-Time
0.36
0.4
0.44
0.33
µs
µs
= V
CELLS
REFIN
V
V
= 16V, V
= 17V,
BATT
DCIN
DHI Minimum Off-Time
0.24
2.5
0.28
= V
CELLS
REFIN
DHI Maximum On-Time
DLOV Supply Current
BST Supply Current
5
5
6
7.5
10
15
ms
µA
µA
I
DLO low
DHI high
DLOV
I
BST
V
V
= 0, V
= 24.5V,
DCIN
BATT
BST
BST Input Quiescent Current
0.3
1
µA
= V = 20V
LX
LX Input Bias Current
V
V
= 28V, V
= V = 20V
150
0.3
500
1
µA
µA
%
DCIN
DCIN
BATT
LX
LX Input Quiescent Current
DHI Maximum Duty Cycle
= 0, V
= V = 20V
BATT LX
99
99.9
Minimum Discontinuous-Mode
Ripple Current
0.5
A
Battery Undervoltage Charge
Current
V
= 3V per cell (RS2 = 15mΩ),
BATT
150
300
450
mA
MAX1908 only, V
rising
BATT
CELLS = GND, MAX1908 only, V
rising
rising
6.1
6.2
9.3
12.4
4
6.3
9.45
12.6
7
BATT
Battery Undervoltage Current
Threshold
V
CELLS = float, MAX1908 only, V
CELLS = V
9.15
12.2
BATT
, MAX1908 only, V
rising
BATT
REFIN
DHI On-Resistance High
DHI On-Resistance Low
DLO On-Resistance High
DLO On-Resistance Low
ERROR AMPLIFIERS
V
V
V
V
- V = 4.5V, I
= +100mA
= -100mA
Ω
Ω
Ω
Ω
BST
LX
DHI
DHI
- V = 4.5V, I
LX
1
3.5
7
BST
= 4.5V, I
= +100mA
= -100mA
4
DLOV
DLOV
DLO
DLO
= 4.5V, I
1
3.5
V
= V
, V = 16.8V,
REFIN
VCTL
LDO BATT
GMV Amplifier Transconductance
GMI Amplifier Transconductance
GMV
GMI
0.0625
0.5
0.125 0.2500 µA/mV
2.0 µA/mV
CELLS = V
V
= V
, V
- V = 75mV
CSIN
1
ICTL
REFIN CSIP
4
_______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = float, CLS =
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REFIN
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = 0°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
A
A
PARAMETER
GMS Amplifier Transconductance
CCI, CCS, CCV Clamp Voltage
LOGIC LEVELS
SYMBOL
CONDITIONS
, V - V = 75mV
MIN
0.5
TYP
1
MAX
2.0
UNITS
µA/mV
mV
GMS
V
= V
CLS
REF CSSP
CSSN
0.25V < V
< 2V
150
300
600
CCV,CCS,CCI
CELLS Input Low Voltage
0.4
V
V
(V
/ 2) -
0.2V
(V
REFIN
REFIN
/ 2) +
0.2V
V
REFIN
/ 2
CELLS Input Float Voltage
CELLS = float
V
REFIN
CELLS Input High Voltage
V
- 0.4V
CELLS Input Bias Current
ACOK AND SHDN
CELLS = 0 or V
-2
+2
28
µA
REFIN
ACOK Input Voltage Range
ACOK Sink Current
0
1
V
mA
µA
V
V
V
= 0.4V, V
= 3V
= 0
ACOK
ACOK
ACIN
ACOK Leakage Current
SHDN Input Voltage Range
= 28V, V
1
ACIN
0
LDO
+1
V
V
= 0 or V
-1
-1
SHDN
LDO
SHDN Input Bias Current
SHDN Threshold
µA
= 0, V
= 5V
SHDN
+1
DCIN
% of
V
falling
22
23.5
1
25
SHDN
V
REFIN
% of
SHDN Threshold Hysteresis
V
REFIN
_______________________________________________________________________________________
5
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = FLOAT, CLS =
REFIN
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = -40°C to +85°C, unless otherwise noted.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE VOLTAGE REGULATION
V
V
V
= V
= V
= V
(2, 3, or 4 cells)
-0.6
-0.6
-0.6
2.5
+0.6
+0.6
+0.6
3.6
VCTL
VCTL
VCTL
REFIN
Battery Regulation Voltage
Accuracy
/ 20 (2, 3, or 4 cells)
%
REFIN
(2, 3, or 4 cells)
LDO
REFIN Range
(Note 1)
V
V
REFIN Undervoltage Lockout
V
falling
1.92
REFIN
CHARGE CURRENT REGULATION
CSIP-to-CSIN Full-Scale Current-
Sense Voltage
V
= V
70.5
79.5
mV
%
ICTL
REFIN
V
V
V
= V
= V
= V
-6
+6
ICTL
ICTL
ICTL
REFIN
REFIN
LDO
Charging Current Accuracy
× 0.6
-7.5
-7.5
+7.5
+7.5
BATT/CSIP/CSIN Input Voltage
Range
0
19
V
µA
A
V
= 0 or V
= 0 or SHDN = 0
ICTL
1
DCIN
CSIP/CSIN Input Current
Charging
650
Cycle-by-Cycle Maximum Current
Limit
I
RS2 = 0.015Ω
6.0
7.5
MAX
ICTL Power-Down Mode
Threshold Voltage
REFIN /
100
REFIN /
33
V
rising
V
ICTL
ICHG Transconductance
G
V
V
V
V
- V
CSIN
- V
CSIN
- V
CSIN
- V
CSIN
= 45mV
= 75mV
= 45mV
= 5mV
2.7
-7.5
-7.5
-40
3.3
+7.5
+7.5
+40
µA/mV
ICHG
CSIP
CSIP
CSIP
CSIP
ICHG Accuracy
%
INPUT CURRENT REGULATION
CSSP-to-CSSN Full-Scale
Current-Sense Voltage
71.25
78.75
mV
%
V
V
= V
= V
-5
+5
CLS
CLS
REF
Input Current-Limit Accuracy
/ 2
-7.5
+7.5
REF
CSSP, CSSN Input Voltage
Range
8
28
V
V
V
= 0
1
DCIN
CSSP
CSSP, CSSN Input Current
µA
= V
= V
> 8V
DCIN
600
REF
3.3
CSSN
CLS Input Range
1.6
2.7
V
IINP Transconductance
G
V
V
V
- V
CSSN
- V
CSSN
- V
CSSN
= 75mV
= 75mV
= 37.5mV
µA/mV
IINP
CSSP
CSSP
CSSP
-7.5
-7.5
+7.5
+7.5
IINP Accuracy
%
6
_______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = FLOAT, CLS =
REFIN
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = -40°C to +85°C, unless otherwise noted.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY AND LDO REGULATOR
DCIN Input Voltage Range
DCIN Quiescent Current
V
8
28
6
V
DCIN
I
8V < V
< 28V
mA
DCIN
DCIN
V
V
= 19V, V
= 0
1
BATT
BATT
DCIN
BATT Input Current
I
µA
BATT
= 2V to 19V, V
= 19.3V
500
5.55
100
DCIN
LDO Output Voltage
LDO Load Regulation
REFERENCE
8V < V
< 28V, no load
5.25
V
DCIN
0 < I
< 10mA
mV
LDO
REF Output Voltage
TRIP POINTS
0 < I
< 500µA
4.065
4.120
V
REF
BATT Power-Fail Threshold
ACIN Threshold
V
V
falling, referred to V
rising
50
150
mV
V
DCIN
ACIN
CSIN
2.007
2.089
SWITCHING REGULATOR
V
V
= 16V, V
= 19V,
BATT
DCIN
DHI Off-Time
0.35
0.24
0.45
µs
µs
= V
CELLS
REFIN
V
V
= 16V, V
= 17V,
BATT
DCIN
DHI Minimum Off-Time
0.33
7.5
= V
CELLS
REFIN
DHI Maximum On-Time
2.5
99
ms
%
DHI Maximum Duty Cycle
Battery Undervoltage Charge
Current
V
= 3V per cell (RS2 = 15mΩ),
BATT
150
450
mA
MAX1908 only, V
rising
BATT
CELLS = GND, MAX1908 only, V
rising
rising
6.09
9.12
6.30
9.45
12.6
7
BATT
Battery Undervoltage Current
Threshold
CELLS = float, MAX1908 only, V
CELLS = V
V
BATT
, MAX1908 only, V
rising 12.18
BATT
REFIN
DHI On-Resistance High
DHI On-Resistance Low
DLO On-Resistance High
DLO On-Resistance Low
ERROR AMPLIFIERS
V
V
V
V
- V = 4.5V, I
= +100mA
= -100mA
Ω
Ω
Ω
Ω
BST
LX
DHI
DHI
- V = 4.5V, I
LX
3.5
7
BST
= 4.5V, I
= +100mA
= -100mA
DLOV
DLOV
DLO
DLO
= 4.5V, I
3.5
V
= V
, V = 16.8V,
VCTL
LDO BATT
GMV Amplifier Transconductance
GMV
0.0625
0.250
µA/mV
CELLS = V
REFIN
GMI Amplifier Transconductance
GMS Amplifier Transconductance
CCI, CCS, CCV Clamp Voltage
LOGIC LEVELS
GMI
V
V
= V
, V
- V = 75mV
CSIN
0.5
0.5
150
2.0
2.0
600
µA/mV
µA/mV
mV
ICTL
CLS
REFIN CSIP
GMS
= V
, V
- V
CSSN
= 75mV
REF CSSP
0.25V < V
< 2V
CCV,CCS,CCI
CELLS Input Low Voltage
0.4
V
_______________________________________________________________________________________
7
Low-Cost Multichemistry Battery Chargers
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
BST
= V
= 18V, V
= V
= V
= 12V, V
= 3V, V
= V
= 0.75 x V
, CELLS = FLOAT, CLS =
REFIN
CSSP
CSSN
BATT
CSIP
CSIN
REFIN
VCTL
ICTL
REF, V
- V = 4.5V, ACIN = GND = PGND = 0, C
= 1µF, LDO = DLOV, C
= 1µF; CCI, CCS, and CCV are compensated
LX
LDO
REF
per Figure 1a; T = -40°C to +85°C, unless otherwise noted.) (Note 2)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
(V
/ 2) -
0.2V
TYP
MAX
UNITS
(V
REFIN
/ 2) +
0.2V
REFIN
CELLS Input Float Voltage
CELLS = float
V
V
REFIN
CELLS Input High Voltage
V
- 0.4V
ACOK AND SHDN
ACOK Input Voltage Range
ACOK Sink Current
0
1
0
28
V
mA
V
V
V
= 0.4V, V
falling
= 3V
ACIN
A COK
S HDN
SHDN Input Voltage Range
LDO
25
% of
REFIN
SHDN Threshold
22
V
Note 1: If both ICTL and VCTL use default mode (connected to LDO), REFIN is not used and can be connected to LDO.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
Typical Operating Characteristics
(Circuit of Figure 1, V
= 20V, T = +25°C, unless otherwise noted.)
A
DCIN
LOAD-TRANSIENT RESPONSE
(STEP IN-LOAD CURRENT)
LOAD-TRANSIENT RESPONSE
LOAD-TRANSIENT RESPONSE
(STEP IN-LOAD CURRENT)
(BATTERY INSERTION AND REMOVAL)
MAX1908 toc01
MAX1908 toc03
MAX1908 toc02
ADAPTER
CURRENT
5A/div
LOAD
CURRENT
5A/div
I
BATT
2A/div
LOAD
CURRENT
5A/div
0
0
0
0
ADAPTER
CURRENT
5A/div
0
V
BATT
5V/div
V_BATT
2V/div
16.8V
CCV
CCI
CHARGE
CURRENT
2A/div
CCI
V_CCI
500mV/div
CCI
V
CCS
CCI 500mV/div
V_CCS
500mV/div
V
CCV 500mV/div
V_BATT
2V/div
CCS
1ms/div
1ms/div
1ms/div
ICTL = LDO
ICTL = LDO
ICTL = LDO
CHARGING CURRENT = 3A
V_BATT = 16.8V
CHARGING CURRENT = 3A
VBATT = 16.8V
VCTL = LDO
LOAD STEP = 0 TO 4A
I_SOURCE LIMIT = 5A
LOAD STEP = 0 TO 4A
I_SOURCE LIMIT = 5A
8
_______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
= 20V, T = +25°C, unless otherwise noted.)
A
DCIN
LINE-TRANSIENT RESPONSE
LDO LOAD REGULATION
LDO LINE REGULATION
MAX1908 toc04
0
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
-0.9
-1.0
0.05
0.04
0.03
0.02
0.01
0
V
DCIN
I
V
= 0
LDO
10V/div
= 5.4V
LDO
V
BATT
500mV/div
-0.01
-0.02
-0.03
-0.04
-0.05
INDUCTOR
CURRENT
500mA/div
V
LDO
= 5.4V
10ms/div
0
1
2
3
4
5
6
7
8
9
10
8
10 12 14 16 18 20 22 24 26 28
(V)
ICTL = LDO
VCTL = LDO
ICHARGE = 3A
LDO CURRENT (mA)
V
IN
LINE STEP 18.5V TO 27.5V
REF VOLTAGE LOAD REGULATION
REF VOLTAGE ERROR vs. TEMPERATURE
EFFICIENCY vs. CHARGE CURRENT
0
-0.01
-0.02
-0.03
-0.04
-0.05
-0.06
-0.07
-0.08
-0.09
-0.10
0.10
0.08
0.06
0.04
0.02
0
100
90
80
V
BATT
= 16V
70
60
V
BATT
= 12V
50
40
V
BATT
= 8V
-0.02
-0.04
-0.06
-0.08
-0.10
30
20
10
0
0
100
200
300
400
500
-40
-15
10
35
60
85
0.01
0.1
1
10
REF CURRENT (µA)
TEMPERATURE (°C)
CHARGE CURRENT (A)
FREQUENCY vs. V - V
BATT VOLTAGE ERROR vs. VCTL
OUTPUT V/I CHARACTERISTICS
IN
BATT
0.5
0.4
0.08
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
500
450
400
350
300
250
200
150
100
50
2 CELLS
3 CELLS
3 CELLS
0.3
0.2
4 CELLS
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
4 CELLS
I
= 3A
CHARGE
4 CELLS
REFIN = 3.3V
NO LOAD
VCTL = ICTL = LDO
0
1.0
0
2
4
6
8
10 12 14 16 18 20 22
0
1
2
3
4
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
VCTL/REFIN (%)
(V - V ) (V)
BATT CURRENT (A)
IN
BATT
_______________________________________________________________________________________
9
Low-Cost Multichemistry Battery Chargers
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
= 20V, T = +25°C, unless otherwise noted.)
A
DCIN
ICHG ERROR vs. CHARGE CURRENT
CURRENT SETTING ERROR vs. ICTL
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
5
4
3
2
1
0
V = 3.3V
REFIN
V
REFIN
= 3.3V
V
BATT
= 16V
V
V
= 12V
= 8V
BATT
BATT
-1
0
0
0.5
1.0
1.5
(A)
2.0
2.5
3.0
0.5
1.0
(V)
1.5
2.0
I
V
BATT
ICTL
IINP ERROR vs. SYSTEM LOAD CURRENT
IINP ERROR vs. INPUT CURRENT
40
30
80
60
20
40
ERROR DUE TO SWITCHING NOISE
I
= 0
BATT
10
20
0
0
-10
-20
-30
-40
-20
-40
-60
-80
SYSTEM LOAD = 0
0
1
2
3
4
0
0.5
1.0
1.5
2.0
SYSTEM LOAD CURRENT (A)
INPUT CURRENT (A)
10 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Pin Description
PIN
1
NAME
DCIN
LDO
CLS
FUNCTION
Charging Voltage Input. Bypass DCIN with a 1µF capacitor to PGND.
2
Device Power Supply. Output of the 5.4V linear regulator supplied from DCIN. Bypass with a 1µF capacitor to GND.
Source Current-Limit Input. Voltage input for setting the current limit of the input source.
4.096V Voltage Reference. Bypass REF with a 1µF capacitor to GND.
3
4
REF
5
CCS
CCI
Input-Current Regulation Loop-Compensation Point. Connect a 0.01µF capacitor to GND.
Output-Current Regulation Loop-Compensation Point. Connect a 0.01µF capacitor to GND.
Voltage Regulation Loop-Compensation Point. Connect 1kΩ in series with 0.1µF capacitor to GND.
6
7
CCV
Shutdown Control Input. Drive SHDN logic low to shut down the MAX1908/MAX8724. Use with a thermistor to
detect a hot battery and suspend charging.
8
9
SHDN
Charge-Current Monitor Output. ICHG is a scaled-down replica of the charger output current. Use ICHG to
monitor the charging current and detect when the chip changes from constant-current mode to constant-
voltage mode. The transconductance of (CSIP - CSIN) to ICHG is 3µA/mV.
ICHG
ACIN
10
11
12
AC Detect Input. Input to an uncommitted comparator. ACIN can be used to detect AC-adapter presence.
ACOK AC Detect Output. High-voltage open-drain output is high impedance when V
is less than V
/ 2.
REF
ACIN
REFIN Reference Input. Allows the ICTL and VCTL inputs to have ratiometric ranges for increased accuracy.
Output Current-Limit Set Input. ICTL input voltage range is V
/ 32 to V
. The device shuts down if
REFIN
REFIN
13
14
15
ICTL
GND
VCTL
BATT
ICTL is forced below V
/ 100. When ICTL is equal to LDO, the set point for CSIP - CSIN is 45mV.
REFIN
Analog Ground
Output-Voltage Limit Set Input. VCTL input voltage range is 0 to V
point is (4.2 x CELLS) V.
. When VCTL is equal to LDO, the set
REFIN
16
17
18
19
20
21
22
23
24
25
26
27
Battery Voltage Input
CELLS Cell Count Input. Trilevel input for setting number of cells. GND = 2 cells, float = 3 cells, REFIN = 4 cells.
CSIN
CSIP
Output Current-Sense Negative Input
Output Current-Sense Positive Input. Connect a current-sense resistor from CSIP to CSIN.
PGND Power Ground
DLO
DLOV
LX
Low-Side Power MOSFET Driver Output. Connect to low-side NMOS gate.
Low-Side Driver Supply. Bypass DLOV with a 1µF capacitor to GND.
High-Side Power MOSFET Driver Power-Return Connection. Connect to the source of the high-side NMOS.
High-Side Power MOSFET Driver Power-Supply Connection. Connect a 0.1µF capacitor from LX to BST.
High-Side Power MOSFET Driver Output. Connect to high-side NMOS gate.
Input Current-Sense Negative Input
BST
DHI
CSSN
CSSP
Input Current-Sense Positive Input. Connect a current-sense resistor from CSSP to CSSN.
Input-Current Monitor Output. IINP is a scaled-down replica of the input current. IINP monitors the total
system current. The transconductance of (CSSP - CSSN) to IINP is 3µA/mV.
28
IINP
______________________________________________________________________________________ 11
Low-Cost Multichemistry Battery Chargers
Setting the Battery Regulation Voltage
Detailed Description
The MAX1908/MAX8724 use a high-accuracy voltage
The MAX1908/MAX8724 include all the functions neces-
regulator for charging voltage. The VCTL input adjusts
the charger output voltage. VCTL control voltage can
sary to charge Li+ batteries. A high-efficiency synchro-
nous-rectified step-down DC-DC converter controls
vary from 0 to V
, providing a 10% adjustment
REFIN
charging voltage and current. The device also includes
input source current limiting and analog inputs for set-
ting the charge current and charge voltage. Control
charge current and voltage using the ICTL and VCTL
inputs, respectively. Both ICTL and VCTL are ratiometric
with respect to REFIN, allowing compatibility with D/As
or microcontrollers (µCs). Ratiometric ICTL and VCTL
improve the accuracy of the charge current and voltage
range on the V
regulation voltage. By limiting the
BATT
adjust range to 10% of the regulation voltage, the exter-
nal resistor mismatch error is reduced from 1% to
0.05% of the regulation voltage. Therefore, an overall
voltage accuracy of better than 0.7% is maintained
while using 1% resistors. The per-cell battery termina-
tion voltage is a function of the battery chemistry.
Consult the battery manufacturer to determine this volt-
age. Connect VCTL to LDO to select the internal default
set point by matching V
to the reference of the
REFIN
host. For standard applications, internal set points for
ICTL and VCTL provide 3A charge current (with 0.015Ω
sense resistor), and 4.2V (per cell) charge voltage.
Connect ICTL and VCTL to LDO to select the internal set
points. The MAX1908 safely conditions overdischarged
cells with 300mA (with 0.015Ω sense resistor) until the
battery-pack voltage exceeds 3.1V × number of series-
connected cells. The SHDN input allows shutdown from
a microcontroller or thermistor.
setting V
= 4.2V × number of cells, or program the
BATT
battery voltage with the following equation:
V
VCTL
V
= CELLS × 4V + 0.4 ×
BATT
V
REFIN
CELLS is the programming input for selecting cell count.
Connect CELLS as shown in Table 1 to charge 2, 3, or 4
Li+ cells. When charging other cell chemistries, use
CELLS to select an output voltage range for the charger.
The DC-DC converter uses external N-channel
MOSFETs as the buck switch and synchronous rectifier
to convert the input voltage to the required charging
current and voltage. The Typical Application Circuit
shown in Figure 1 uses a µC to control charging cur-
rent, while Figure 2 shows a typical application with
charging voltage and current fixed to specific values
for the application. The voltage at ICTL and the value of
RS2 set the charging current. The DC-DC converter
generates the control signals for the external MOSFETs
to regulate the voltage and the current set by the VCTL,
ICTL, and CELLS inputs.
The internal error amplifier (GMV) maintains voltage
regulation (Figure 3). The voltage error amplifier is
compensated at CCV. The component values shown in
Figures 1 and 2 provide suitable performance for most
applications. Individual compensation of the voltage reg-
ulation and current-regulation loops allows for optimal
compensation (see the Compensation section).
Table 1. Cell-Count Programming
The MAX1908/MAX8724 feature a voltage-regulation
loop (CCV) and two current-regulation loops (CCI and
CCS). The CCV voltage-regulation loop monitors BATT
to ensure that its voltage does not exceed the voltage
set by VCTL. The CCI battery current-regulation loop
monitors current delivered to BATT to ensure that it
does not exceed the current limit set by ICTL. A third
loop (CCS) takes control and reduces the battery-
charging current when the sum of the system load and
the battery-charging input current exceeds the input
current limit set by CLS.
CELLS
CELL COUNT
GND
2
3
4
Float
V
REFIN
12 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Typical Application Circuits
RS1
0.01Ω
TO EXTERNAL
LOAD
AC ADAPTER INPUT
8.5V TO 28V
D1
C1
2 × 10µF
0.1µF
0.1µF
D2
CSSP
DCIN
CSSN
CELLS
R6
59kΩ
1%
(FLOAT-THREE CELLS SELECT)
R7
19.6kΩ
1%
C5
1µF
LDO
C13
R13
1µF
33Ω
LDO
VCTL
D3
BST
D/A OUTPUT
ICTL
DLOV
12.6V OUTPUT VOLTAGE
C15
0.1µF
C16
1µF
V
CC
REFIN
R8
1MΩ
ACIN
N1a
DHI
LX
ACOK
SHDN
ICHG
OUTPUT
N1b
DLO
A/D INPUT
MAX1908
MAX8724
L1
PGND
10µH
A/D INPUT
IINP
CCV
CSIP
C14
C20
R10
R9
R5
0.1µF
0.1µF
10kΩ
20kΩ
1kΩ
RS2
HOST
0.015Ω
C11
0.1µF
CSIN
BATT
GND
CCI
+
BATT
CCS
C9
0.01µF
C10
0.01µF
C4
22µF
REF
CLS
AVDD/REF
R19, R20, R21
10kΩ
7.5A INPUT
CURRENT LIMIT
C12
1µF
SMART
BATTERY
SCL
SDA
SCL
SDA
A/D INPUT
GND
TEMP
BATT-
PGND
GND
Figure 1. µC-Controlled Typical Application Circuit
______________________________________________________________________________________ 13
Low-Cost Multichemistry Battery Chargers
Typical Application Circuits (continued)
AC ADAPTER
INPUT
8.5V TO 28V
RS1
0.01Ω
TO EXTERNAL
LOAD
P1
R11
15kΩ
C1
2 × 10µF
0.01µF 0.01µF
R12
12kΩ
REFIN (4 CELLS SELECT)
CSSP
ACOK
CSSN
D2
R6
59kΩ
1%
CELLS
R7
19.6kΩ
1%
DCIN
LDO
C5
1µF
LDO
R14
10.5kΩ
1%
VCTL
LDO
C13
R13
1µF
33Ω
D3
REFIN
BST
R15
8.25kΩ
1%
DLOV
C15
C16
0.1µF
1µF
ICTL
N1a
16.8V OUTPUT VOLTAGE
2.5A CHARGE LIMIT
R16
8.25kΩ
1%
DHI
LX
ACIN
R19
C12
10kΩ
1%
1.5nF
N1b
FROM HOST µP
(SHUTDOWN)
N
DLO
MAX1908
MAX8724
L1
10µH
SHDN
PGND
R20
10kΩ
1%
ICHG
IINP
CSIP
CCV
R5
1kΩ
RS2
0.015Ω
C11
0.1µF
CSIN
BATT
GND
CCI
+
BATT
CCS
C9
0.01µF
C10
0.01µF
C4
22µF
BATTERY
THM
BATT-
REF
CLS
C12
1µF
R17
19.1kΩ
1%
PGND GND
R18
22kΩ
1%
4A INPUT CURRENT LIMIT
Figure 2. Typical Application Circuit with Fixed Charging Parameters
14 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Functional Diagram
MAX1908
MAX8724
DCIN
SHDN
GND
23.5%
REFIN
LDO
RDY
5.4V
LINEAR
REGULATOR
4.096V
REFERENCE
REF
LOGIC
BLOCK
GND
1/55
ICTL
REFIN
SRDY
ACIN
ACOK
DCIN
X
N
REF/2
CCS
CLS
75mV
REF
IINP
GM
GM
GMS
CSSP
CSSN
LEVEL
SHIFTER
ICHG
CSI
CSIP
CSIN
LEVEL
SHIFTER
BST
DHI
LX
GMI
75mV
REFIN
LEVEL
SHIFTER
ICTL
CCI
X
DRIVER
MAX1908 ONLY
3.1V/CELL
BATT
BAT_UV
LVC
DC-DC
LVC
CONVERTER
R1
REFIN
GMV
CELL
SELECT
LOGIC
CELLS
DLOV
DLO
DRIVER
CCV
PGND
400mV
REFIN
VCTL
4V
X
Figure 3. Functional Diagram
______________________________________________________________________________________ 15
Low-Cost Multichemistry Battery Chargers
AC adapter voltage. An internal amplifier compares the
voltage between CSSP and CSSN to the voltage at
Setting the Charging-Current Limit
The ICTL input sets the maximum charging current. The
current is set by current-sense resistor RS2, connected
between CSIP and CSIN. The full-scale differential
voltage between CSIP and CSIN is 75mV; thus, for a
0.015Ω sense resistor, the maximum charging current
is 5A. Battery-charging current is programmed with
ICTL using the equation:
CLS. V
can be set by a resistive divider between
CLS
REF and GND. Connect CLS to REF for the full-scale
input current limit.
The input current is the sum of the device current, the
charger input current, and the load current. The device
current is minimal (3.8mA) in comparison to the charge
and load currents. Determine the actual input current
required as follows:
V
0.075
RS2
ICTL
I
=
×
CHG
V
REFIN
I
× V
BATT
CHG
I
= I
+
INPUT
LOAD
The input voltage range for ICTL is V
/ 32 to
REFIN
V
× η
IN
V
V
. The device shuts down if ICTL is forced below
REFIN
REFIN
where η is the efficiency of the DC-DC converter.
determines the reference voltage of the GMS
/ 100 (min).
V
Connect ICTL to LDO to select the internal default full-
scale charge-current sense voltage of 45mV. The
charge current when ICTL = LDO is:
CLS
error amplifier. Sense resistor RS1 and V
determine
CLS
the maximum allowable input current. Calculate the
input current limit as follows:
0.045V
RS2
I
=
V
0.075
RS1
CHG
CLS
I
=
×
INPUT
V
REF
Once the input current limit is reached, the charging
current is reduced until the input current is at the
desired threshold.
where RS2 is 0.015Ω, providing a charge-current set
point of 3A.
The current at the ICHG output is a scaled-down replica
of the battery output current being sensed across CSIP
and CSIN (see the Current Measurement section).
When choosing the current-sense resistor, note that the
voltage drop across this resistor causes further power
loss, reducing efficiency. Choose the smallest value for
RS1 that achieves the accuracy requirement for the
input current-limit set point.
When choosing the current-sense resistor, note that the
voltage drop across this resistor causes further power
loss, reducing efficiency. However, adjusting ICTL to
reduce the voltage across the current-sense resistor
can degrade accuracy due to the smaller signal to the
input of the current-sense amplifier. The charging cur-
rent-error amplifier (GMI) is compensated at CCI (see
the Compensation section).
Conditioning Charge
The MAX1908 includes a battery voltage comparator
that allows a conditioning charge of overdischarged
Li+ battery packs. If the battery-pack voltage is less
than 3.1V × number of cells programmed by CELLS,
the MAX1908 charges the battery with 300mA current
when using sense resistor RS2 = 0.015Ω. After the
battery voltage exceeds the conditioning charge
threshold, the MAX1908 resumes full-charge mode,
charging to the programmed voltage and current limits.
The MAX8724 does not offer this feature.
Setting the Input Current Limit
The total input current (from an AC adapter or other DC
source) is a function of the system supply current and
the battery-charging current. The input current regulator
limits the input current by reducing the charging
current when the input current exceeds the input
current-limit set point. System current normally
fluctuates as portions of the system are powered up or
down. Without input current regulation, the source must
be able to supply the maximum system current and the
maximum charger input current simultaneously. By
using the input current limiter, the current capability of
the AC adapter can be lowered, reducing system cost.
AC Adapter Detection
Connect the AC adapter voltage through a resistive
divider to ACIN to detect when AC power is available,
as shown in Figure 1. ACIN voltage rising trip point is
V
REF
/ 2 with 20mV hysteresis. ACOK is an open-drain
output and is high impedance when ACIN is less than
/ 2. Since ACOK can withstand 30V (max), ACOK
V
REF
can drive a P-channel MOSFET directly at the charger
input, providing a lower dropout voltage than a
Schottky diode (Figure 2).
The MAX1908/MAX8724 limit the battery charge current
when the input current-limit threshold is exceeded,
ensuring the battery charger does not load down the
16 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
CCV, CCI, CCS, and LVC Control Blocks
The MAX1908/MAX8724 control input current (CCS
control loop), charge current (CCI control loop), or
charge voltage (CCV control loop), depending on the
operating condition.
Current Measurement
Use ICHG to monitor the battery charging current being
sensed across CSIP and CSIN. The ICHG voltage is
proportional to the output current by the equation:
V
= I
x RS2 x G
x R9
ICHG
CHG
ICHG
The three control loops, CCV, CCI, and CCS are brought
together internally at the LVC amplifier (lowest voltage
clamp). The output of the LVC amplifier is the feedback
control signal for the DC-DC controller. The output of the
where I
is the battery charging current, G
is
CHG
ICHG
the transconductance of ICHG (3µA/mV typ), and R9 is
the resistor connected between ICHG and ground.
Leave ICHG unconnected if not used.
G
amplifier that is the lowest sets the output of the LVC
M
Use IINP to monitor the system input current being
sensed across CSSP and CSSN. The voltage of IINP is
proportional to the input current by the equation:
amplifier and also clamps the other two control loops to
within 0.3V above the control point. Clamping the other
two control loops close to the lowest control loop ensures
fast transition with minimal overshoot when switching
between different control loops.
V
= I
x RS2 x G
x R10
IINP
INPUT
IINP
where I
is the DC current being supplied by the AC
INPUT
adapter power, G
is the transconductance of IINP
IINP
DC-DC Controller
The MAX1908/MAX8724 feature a variable off-time, cycle-
by-cycle current-mode control scheme. Depending upon
the conditions, the MAX1908/MAX8724 work in continu-
ous or discontinuous-conduction mode.
(3µA/mV typ), and R10 is the resistor connected between
IINP and ground. ICHG and IINP have a 0 to 3.5V output
voltage range. Leave IINP unconnected if not used.
LDO Regulator
LDO provides a 5.4V supply derived from DCIN and
can deliver up to 10mA of load current. The MOSFET
drivers are powered by DLOV and BST, which must be
connected to LDO as shown in Figure 1. LDO supplies
the 4.096V reference (REF) and most of the control cir-
cuitry. Bypass LDO with a 1µF capacitor to GND.
Continuous-Conduction Mode
With sufficient charger loading, the MAX1908/MAX8724
operate in continuous-conduction mode (inductor current
never reaches zero) switching at 400kHz if the BATT
voltage is within the following range:
3.1V x (number of cells) < V
< (0.88 x V
)
DCIN
BATT
Shutdown
The MAX1908/MAX8724 feature a low-power shutdown
mode. Driving SHDN low shuts down the MAX1908/
MAX8724. In shutdown, the DC-DC converter is dis-
abled and CCI, CCS, and CCV are pulled to ground.
The IINP and ACOK outputs continue to function.
The operation of the DC-DC controller is controlled by
the following four comparators as shown in Figure 4:
IMIN—Compares the control point (LVC) against 0.15V
(typ). If IMIN output is low, then a new cycle cannot
begin.
CCMP—Compares the control point (LVC) against the
charging current (CSI). The high-side MOSFET on-time
is terminated if the CCMP output is high.
SHDN can be driven by a thermistor to allow automatic
shutdown of the MAX1908/MAX8724 when the battery
pack is hot. The shutdown falling threshold is 23.5%
(typ) of V
with 1% V
hysteresis to provide
REFIN
REFIN
IMAX—Compares the charging current (CSI) to 6A
(RS2 = 0.015Ω). The high-side MOSFET on-time is ter-
minated if the IMAX output is high and a new cycle
cannot begin until IMAX goes low.
smooth shutdown when driven by a thermistor.
DC-DC Converter
The MAX1908/MAX8724 employ a buck regulator with
a bootstrapped NMOS high-side switch and a low-side
NMOS synchronous rectifier.
ZCMP—Compares the charging current (CSI) to 33mA
(RS2 = 0.015Ω). If ZCMP output is high, then both
MOSFETs are turned off.
______________________________________________________________________________________ 17
Low-Cost Multichemistry Battery Chargers
DC-DC Functional Diagram
5ms
S
R
CSSP
AC ADAPTER
RESET
1.8V
BST
CSS
X20
RS1
LDO
D3
IMAX
CCMP
IMIN
MAX1908
MAX8724
CSSN
BST
Q
N1a
DHI
LX
R
S
Q
C
BST
DHI
CHG
Q
L1
0.15V
0.1V
N1b
DLO
DLO
t
OFF
GENERATOR
CSIP
ZCMP
CSI
X20
RS2
CSIN
BATT
GMS
GMI
LVC
C
OUT
BATTERY
GMV
SETV
CONTROL SETI
CELL
SELECT
LOGIC
CLS
CELLS
CCS CCI
CCV
Figure 4. DC-DC Functional Diagram
18 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
In normal operation, the controller starts a new cycle by
turning on the high-side N-channel MOSFET and
turning off the low-side N-channel MOSFET. When the
charge current is greater than the control point (LVC),
CCMP goes high and the off-time is started. The
off-time turns off the high-side N-channel MOSFET and
turns on the low-side N-channel MOSFET. The opera-
tional frequency is governed by the off-time and is
Discontinuous Conduction
The MAX1908/MAX8724 enter discontinuous-conduction
mode when the output of the LVC control point falls below
0.15V. For RS2 = 0.015Ω, this corresponds to 0.5A:
0.15V
20×RS2
I
=
= 0.5A for RS2 = 0.015Ω
MIN
dependent upon V
and V
. The off-time is set
BATT
DCIN
In discontinuous mode, a new cycle is not started until
the LVC voltage rises above 0.15V. Discontinuous-
mode operation can occur during conditioning charge
of overdischarged battery packs, when the charge cur-
rent has been reduced sufficiently by the CCS control
loop, or when the battery pack is near full charge (con-
stant voltage charging mode).
by the following equations:
V
− V
DCIN
BATT
t
= 2.5µs ×
OFF
t
V
DCIN
L ×I
RIPPLE
− V
BATT
=
ON
MOSFET Drivers
The low-side driver output DLO switches between
PGND and DLOV. DLOV is usually connected through
a filter to LDO. The high-side driver output DHI is boot-
V
CSSN
where:
strapped off LX and switches between V and V
.
BST
LX
V
× t
OFF
L
BATT
I
=
When the low-side driver turns on, BST rises to one
diode voltage below DLOV.
RIPPLE
Filter DLOV with a lowpass filter whose cutoff frequency
is approximately 5kHz (Figure 1):
1
+ t
f =
t
ON
OFF
1
1
f =
=
= 4.8kHz
C
2πRC 2π × 33Ω ×1µF
These equations result in fixed-frequency operation
over the most common operating conditions.
Dropout Operation
At the end of the fixed off-time, another cycle begins if
the control point (LVC) is greater than 0.15V, IMIN =
high, and the peak charge current is less than 6A (RS2
= 0.015Ω), IMAX = high. If the charge current exceeds
The MAX1908/MAX8724 have 99% duty-cycle capability
with a 5ms (max) on-time and 0.3µs (min) off-time. This
allows the charger to achieve dropout performance limit-
ed only by resistive losses in the DC-DC converter com-
ponents (D1, N1, RS1, and RS2, Figure 1). Replacing
diode D1 with a P-channel MOSFET driven by ACOK
improves dropout performance (Figure 2). The dropout
voltage is set by the difference between DCIN and CSIN.
When the dropout voltage falls below 100mV, the charger
is disabled; 200mV hysteresis ensures that the charger
does not turn back on until the dropout voltage rises to
300mV.
I
, the on-time is terminated by the IMAX comparator.
MAX
IMAX governs the maximum cycle-by-cycle current limit
and is internally set to 6A (RS2 = 0.015Ω). IMAX pro-
tects against sudden overcurrent faults.
If during the off-time the inductor current goes to zero,
ZCMP = high, both the high- and low-side MOSFETs
are turned off until another cycle is ready to begin.
There is a minimum 0.3µs off-time when the (V
-
DCIN
≥ 0.88 ×
V
V
) differential becomes too small. If V
BATT
DCIN
BATT
Compensation
Each of the three regulation loops—input current limit,
charging current limit, and charging voltage limit—are
compensated separately using CCS, CCI, and CCV,
respectively.
, then the threshold for minimum off-time is
is fixed at 0.3µs. A maximum on-
reached and the t
OFF
time of 5ms allows the controller to achieve >99% duty
cycle in continuous-conduction mode. The switching
frequency in this mode varies according to the equation:
1
f =
L ×I
RIPPLE
+ 0.3µs
V
− V
CSSN
BATT
______________________________________________________________________________________ 19
Low-Cost Multichemistry Battery Chargers
where R varies with load according to R = V / I
BATT CHG.
L
L
Output zero due to output capacitor ESR:
BATT
1
f
=
GM
OUT
Z _ESR
2πR
× C
OUT
ESR
The loop transfer function is given by:
LTF = GM ×R ×GMV ×R ×
OGMV
R
R
L
ESR
CCV
OUT
L
GMV
C
OUT
1+sC
× R
1+sC × R
(
)(
)
)
OUT
ESR CV CV
1+sC × R
1+sC
)(
× R
L
(
CV
OGMV
OUT
R
CV
R
OGMV
REF
Assuming the compensation pole is a very low
frequency, and the output zero is a much higher fre-
quency, the crossover frequency is given by:
C
CV
GMV × R
× GM
OUT
CV
f
=
CO_CV
Figure 5. CCV Loop Diagram
2πC
OUT
CCV Loop Definitions
Compensation of the CCV loop depends on the para-
meters and components shown in Figure 5. C and
To calculate R and C values of the circuit of Figure 2:
Cells = 4
CV
CV
CV
C
OUT
= 22µF
R
are the CCV loop compensation capacitor and
CV
V
I
= 16.8V
= 2.5A
BATT
CHG
series resistor. R
(ESR) of the charger output capacitor (C
equivalent charger output load, where R = V
CHG
is the equivalent series resistance
ESR
). R is the
L
OUT
/
BATT
GMV = 0.125µA/mV
L
I
. The equivalent output impedance of the GMV
GM
= 3.33A/V
OUT
amplifier, R
≥ 10MΩ. The voltage amplifier
OGMV
R
OGMV
= 10MΩ
transconductance, GMV = 0.125µA/mV. The DC-DC
converter transconductance, GM = 3.33A/V:
f = 400kHz
OUT
Choose crossover frequency to be 1/5th the
MAX1908’s 400kHz switching frequency:
1
GM
=
OUT
A
× RS2
CSI
GMV × R
× GM
OUT
CV
f
=
= 80kHz
CO_CV
2πC
OUT
where A
= 20, and RS2 is the charging current-
CSI
sense resistor in the Typical Application Circuits.
Solving yields R = 26kΩ.
CV
The compensation pole is given by:
Conservatively set R = 1kΩ, which sets the crossover
CV
frequency at:
1
f
=
P _CV
f
= 3kHz
2πR
× C
CV
CO_CV
OGMV
Choose the output-capacitor ESR such that the output-
capacitor zero is 10 times the crossover frequency:
The compensation zero is given by:
1
1
f
=
R
=
= 0.24Ω
Z _CV
ESR
2πR
× C
CV
2π ×10× f
×C
OUT
CV
CO_CV
The output pole is given by:
1
f
=
= 2.412MHz
Z_ESR
2πR
×C
1
ESR
OUT
f
=
P _OUT
2πR × C
L
OUT
20 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
The 22µF ceramic capacitor has a typical ESR of
CCI Loop Definitions
0.003Ω, which sets the output zero at 2.412MHz.
Compensation of the CCI loop depends on the parame-
ters and components shown in Figure 7. C is the CCI
CI
The output pole is set at:
loop compensation capacitor. A
is the internal gain
CSI
of the current-sense amplifier. RS2 is the charge cur-
1
f
=
= 1.08kHz
P _OUT
rent-sense resistor, RS2 = 15mΩ. R
is the equiva-
OGMI
2πR × C
L
OUT
lent output impedance of the GMI amplifier ≥ 10MΩ.
GMI is the charge-current amplifier transconductance
where:
= 1µA/mV. GM
is the DC-DC converter transcon-
OUT
ductance = 3.3A/V. The CCI loop is a single-pole sys-
∆V
∆I
BATT
CHG
tem with a dominant pole compensation set by f
:
R
=
= Battery ESR
P_CI
L
1
f
=
P _CI
Set the compensation zero (f
) such that it is equiv-
Z_CV
2πR
× C
CI
OGMI
alent to the output pole (f
= 1.08kHz), effectively
P_OUT
producing a pole-zero cancellation and maintaining a
single-pole system response:
The loop transfer function is given by:
R
1
OGMI
LTF = GM
× A ×RS2×GMI
CSI
f
=
OUT
Z _CV
1+sR
×C
2πR
× C
OGMI
CI
CV
CV
Since:
1
C
=
=147nF
1
CV
2πR ×1.08kHz
GM
=
CV
OUT
A
× RS2
CSI
Choose C
= 100nF, which sets the compensation
CV
The loop transfer function simplifies to:
zero (f
) at 1.6kHz. This sets the compensation pole:
Z_CV
1
R
OGMI
f
=
= 0.16Hz
LTF = GMI ×
P _CV
2πR
× C
CV
1+sR
×C
OGMV
OGMI
CI
CCV LOOP PHASE
vs. FREQUENCY
CCV LOOP GAIN
vs. FREQUENCY
80
60
-45
-60
40
-75
20
-90
0
-105
-120
-135
-20
-40
-60
1
10
100
1k
10k
100k
1M
1
10
100
1k
10k
100k
1M
FREQUENCY (Hz)
FREQUENCY (Hz)
Figure 6. CCV Loop Gain/Phase vs. Frequency
______________________________________________________________________________________ 21
Low-Cost Multichemistry Battery Chargers
To calculate the CCI loop compensation pole, C :
CI
GMI = 1µA/mV
CSIP
CSIN
GM
= 3.33A/V
OUT
GM
OUT
R
= 10MΩ
OGMI
RS2
CSI
f = 400kHz
Choose crossover frequency f
to be 1/5th the
CI
CO_
MAX1908/MAX8724 switching frequency:
GMI
CCI
C
f
=
= 80kHz
CO_CI
2πC
GMI
CI
Solving for C , C = 2nF.
CI CI
R
OGMI
CI
ICTL
To be conservative, set C = 10nF, which sets the
CI
crossover frequency at:
GMI
2π10nF
f
=
= 16kHz
Figure 7. CCI Loop Diagram
CO_CI
The crossover frequency is given by:
GMI
The compensation pole, f
is set at:
P_CI
f
=
CO_CI
GMI
2πC
CI
f
=
= 0.0016Hz
P_CI
2πR
×C
CI
OGMI
The CCI loop dominant compensation pole:
1
CCS Loop Definitions
Compensation of the CCS loop depends on the parame-
f
=
P _CI
ters and components shown in Figure 9. C is the CCS
CS
2πR
× C
CI
OGMI
loop compensation capacitor. A
is the internal gain of
CSS
the current-sense amplifier. RS1 is the input current-
where the GMI amplifier output impedance, R
10MΩ.
=
OGMI
sense resistor, RS1 = 10mΩ. R
output impedance of the GMS amplifier ≥ 10MΩ. GMS is
is the equivalent
OGMS
CCI LOOP GAIN
vs. FREQUENCY
CCI LOOP PHASE
vs. FREQUENCY
100
0
80
60
-15
-30
40
-45
20
-60
0
-75
-20
-40
-60
-90
-105
0.1
1
10 100 1k
FREQUENCY (Hz)
10k 100k 1M
0.1
1
10 100 1k
FREQUENCY (Hz)
10k 100k 1M
Figure 8. CCI Loop Gain/Phase vs. Frequency
22 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
the charge-current amplifier transconductance = 1µA/mV.
GM is the DC-DC converter transconductance =
IN
3.3A/V. The CCS loop is a single-pole system with a dom-
CSSP
CSSN
inant pole compensation set by f
:
P_CS
GM
IN
RS1
CSS
1
f
=
P _CS
2πR
× C
CS
OGMS
The loop transfer function is given by:
CCS
C
R
OGMS
LTF = GM × A
×RS1×GMS×
CSS
GMS
IN
1+sR
×C
OGMS
CS
R
OGMS
Since:
CS
CLS
1
GM
=
IN
A
× RS1
CSS
Then, the loop transfer function simplifies to:
Figure 9. CCS Loop Diagram
R
OGMS
The CCS loop dominant compensation pole:
1
LTF = GMS×
1+sR
×C
OGMS
CS
f
=
P _CS
2πR
× C
CS
OGMS
The crossover frequency is given by:
GMS
where the GMS amplifier output impedance, R
10MΩ.
=
OGMS
f
=
CO_CS
2πC
CS
To calculate the CCI loop compensation pole, C
GMS = 1µA/mV
:
CS
GM = 3.33A/V
IN
R
OGMS
= 10MΩ
f = 400kHz
CCS LOOP GAIN
vs. FREQUENCY
CCS LOOP PHASE
vs. FREQUENCY
100
0
-15
-30
-45
-60
-75
-90
80
60
40
20
0
-20
-40
-60
-105
0.1
0.1
1
10 100 1k
FREQUENCY (Hz)
10k 100k 1M
1
10 100 1k
FREQUENCY (Hz)
10k 100k 1M
Figure 10. CCS Loop Gain/Phase vs. Frequency
______________________________________________________________________________________ 23
Low-Cost Multichemistry Battery Chargers
Choose crossover frequency f
to be 1/5th the
where:
CO_CS
MAX1908/MAX8724 switching frequency:
t
= 2.5µs × (V
– V ) / V
BATT DCIN
OFF
DCIN
V
< 0.88 × V
BATT
DCIN
GMS
f
=
= 80kHz
CO_CS
or:
2πC
CS
t
= 0.3µs
OFF
Solving for C , C = 2nF.
CS CS
V
> 0.88 × V
DCIN
BATT
To be conservative, set C
crossover frequency at:
= 10nF, which sets the
CS
Figure 11 illustrates the variation of ripple current vs.
battery voltage when charging at 3A with a fixed input
voltage of 19V.
GMS
2π10nF
f
=
= 16kHz
Higher inductor values decrease the ripple current.
Smaller inductor values require higher saturation cur-
rent capabilities and degrade efficiency. Designs for
ripple current, I
good balance between inductor size and efficiency.
CO_CS
The compensation pole, f
is set at:
P_CS
= 0.3 × I
usually result in a
RIPPLE
CHG
1
f
=
= 0.0016Hz
P_CS
Input Capacitor
Input capacitor C1 must be able to handle the input
ripple current. At high charging currents, the DC-DC
converter operates in continuous conduction. In this
case, the ripple current of the input capacitor can be
approximated by the following equation:
2πR
×C
CS
OGMS
Component Selection
Table 2 lists the recommended components and refers
to the circuit of Figure 2. The following sections
describe how to select these components.
Inductor Selection
Inductor L1 provides power to the battery while it is
being charged. It must have a saturation current of at
2
I
= I
D − D
C1 CHG
where:
= input capacitor ripple current.
least the charge current (I
), plus 1/2 the current rip-
CHG
I
ple I
:
C1
RIPPLE
D = DC-DC converter duty ratio.
= battery-charging current.
I
= I
+ (1/2) I
CHG RIPPLE
SAT
I
Ripple current varies according to the equation:
CHG
Input capacitor C1 must be sized to handle the maxi-
mum ripple current that occurs during continuous con-
duction. The maximum input ripple current occurs at
50% duty cycle; thus, the worst-case input ripple cur-
I
= (V
) × t
/ L
RIPPLE
BATT
OFF
RIPPLE CURRENT vs. V
BATT
rent is 0.5 × I
. If the input-to-output voltage ratio is
CHG
1.5
1.0
0.5
0
such that the DC-DC converter does not operate at a
50% duty cycle, then the worst-case capacitor current
occurs where the duty cycle is nearest 50%.
3 CELLS
4 CELLS
The input capacitor ESR times the input ripple current
sets the ripple voltage at the input, and should not
exceed 0.5V ripple. Choose the ESR of C1 according to:
0.5V
ESR
<
C1
I
V
DCIN
= 19V
C1
VCTL = ICTL = LDO
The input capacitor size should allow minimal output
voltage sag at the highest switching frequency:
8
9
10 11 12 13 14 15 16 17 18
(V)
V
BATT
I
dV
dt
C1
2
= C1
Figure 11. MAX1908 Ripple Current vs. Battery Voltage
24 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
where dV is the maximum voltage sag of 0.5V while
delivering energy to the inductor during the high-side
MOSFET on-time, and dt is the period at highest oper-
ating frequency (400kHz):
the MOSFET. Choose N1b with either an internal
Schottky diode or body diode capable of carrying the
maximum charging current during the dead time. The
Schottky diode D3 provides the supply current to the
high-side MOSFET driver.
I
2.5µs
C1
C1>
×
Layout and Bypassing
2
0.5V
Bypass DCIN with a 1µF capacitor to power ground
(Figure 1). D2 protects the MAX1908/MAX8724 when
the DC power source input is reversed. A signal diode
for D2 is adequate because DCIN only powers the
MAX1908 internal circuitry. Bypass LDO, REF, CCV,
CCI, CCS, ICHG, and IINP to analog ground. Bypass
DLOV to power ground.
Both tantalum and ceramic capacitors are suitable in
most applications. For equivalent size and voltage
rating, tantalum capacitors have higher capacitance,
but also higher ESR than ceramic capacitors. This
makes it more critical to consider ripple current and
power-dissipation ratings when using tantalum capaci-
tors. A single ceramic capacitor often can replace two
tantalum capacitors in parallel.
Good PC board layout is required to achieve specified
noise, efficiency, and stable performance. The PC
board layout artist must be given explicit instructions—
preferably, a pencil sketch showing the placement of
the power-switching components and high-current rout-
ing. Refer to the PC board layout in the MAX1908 eval-
uation kit for examples. Separate analog and power
grounds are essential for optimum performance.
Output Capacitor
The output capacitor absorbs the inductor ripple cur-
rent. The output capacitor impedance must be signifi-
cantly less than that of the battery to ensure that it
absorbs the ripple current. Both the capacitance and
ESR rating of the capacitor are important for its effec-
tiveness as a filter and to ensure stability of the DC-DC
converter (see the Compensation section). Either tanta-
lum or ceramic capacitors can be used for the output
filter capacitor.
Use the following step-by-step guide:
1) Place the high-power connections first, with their
grounds adjacent:
MOSFETs and Diodes
Schottky diode D1 provides power to the load when the
AC adapter is inserted. This diode must be able to
deliver the maximum current as set by RS1. For
reduced power dissipation and improved dropout per-
formance, replace D1 with a P-channel MOSFET (P1)
as shown in Figure 2. Take caution not to exceed the
a) Minimize the current-sense resistor trace lengths,
and ensure accurate current sensing with Kelvin
connections.
b) Minimize ground trace lengths in the high-current
paths.
c) Minimize other trace lengths in the high-current
paths.
maximum V
limit the V
of P1. Choose resistors R11 and R12 to
GS
.
d) Use > 5mm wide traces.
GS
The N-channel MOSFETs (N1a, N1b) are the switching
devices for the buck controller. High-side switch N1a
should have a current rating of at least the maximum
charge current plus one-half the ripple current and
e) Connect C1 to high-side MOSFET (10mm max
length).
f) LX node (MOSFETs, inductor (15mm max
length)).
have an on-resistance (R
) that meets the power
DS(ON)
Ideally, surface-mount power components are flush
against one another with their ground terminals
almost touching. These high-current grounds are
then connected to each other with a wide, filled zone
of top-layer copper, so they do not go through vias.
dissipation requirements of the MOSFET. The driver for
N1a is powered by BST. The gate-drive requirement for
N1a should be less than 10mA. Select a MOSFET with a
low total gate charge (Q
) and determine the
GATE
required drive current by I
= Q
× f (where f is
GATE
GATE
the DC-DC converter’s maximum switching frequency).
The resulting top-layer power ground plane is
connected to the normal ground plane at the
MAX1908/MAX8724s’ backside exposed pad.
Other high-current paths should also be minimized,
but focusing primarily on short ground and current-
sense connections eliminates most PC board lay-
out problems.
The low-side switch (N1b) has the same current rating
and power dissipation requirements as N1a, and
should have a total gate charge less than 10nC. N2 is
used to provide the starting charge to the BST capacitor
(C15). During the dead time (50ns, typ) between N1a
and N1b, the current is carried by the body diode of
______________________________________________________________________________________ 25
Low-Cost Multichemistry Battery Chargers
2) Place the IC and signal components. Keep the
main switching node (LX node) away from sensitive
analog components (current-sense traces and REF
capacitor). Important: The IC must be no further
than 10mm from the current-sense resistors.
current-sense lines and REF. Place ceramic
bypass capacitors close to the IC. The bulk capac-
itors can be placed further away.
3) Use a single-point star ground placed directly
below the part at the backside exposed pad of the
MAX1908/MAX8724. Connect the power ground
and normal ground to this node.
Keep the gate-drive traces (DHI, DLO, and BST)
shorter than 20mm, and route them away from the
Table 2. Component List for Circuit of Figure 2
DESIGNATION QTY
DESCRIPTION
Schottky diode
DESIGNATION QTY
DESCRIPTION
10µF, 50V 2220-size ceramic
capacitors
TDK C5750X7R1H106M
D3
1
Central Semiconductor CMPSH1-4
C1
C4
2
1
10µH, 4.4A inductor
Sumida CDRH104R-100NC
TOKO 919AS-100M
L1
1
22µF, 25V 2220-size ceramic
capacitor
TDK C5750X7R1E226M
Dual, N-channel, 8-pin SO MOSFET
Fairchild FDS6990A or FDS6990S
N1
P1
1
1
1µF, 25V X7R ceramic capacitor
(1206)
Murata GRM31MR71E105K
Taiyo Yuden TMK316BJ105KL
TDK C3216X7R1E105K
Single, P-channel, 8-pin SO MOSFET
Fairchild FDS6675
C5
1
2
4
R5
R6
1
1
1
1
1
1
1
2
1
1
2
1kΩ 5% resistor (0603)
59kΩ 1% resistor (0603)
19.6kΩ 1% resistor (0603)
12kΩ 5% resistor (0603)
15kΩ 5% resistor (0603)
33Ω 5% resistor (0603)
10.5kΩ 1% resistor (0603)
8.25kΩ 1% resistors (0603)
19.1kΩ 1% resistor (0603)
22kΩ 1% resistor (0603)
10kΩ 1% resistors (0603)
0.01µF, 16V ceramic capacitors (0402)
Murata GRP155R71E103K
Taiyo Yuden EMK105BJ103KV
TDK C1005X7R1E103K
R7
C9, C10
R11
R12
R13
0.1µF, 25V X7R ceramic capacitors
(0603)
Murata GRM188R71E104K
TDK C1608X7R1E104K
R14
C11, C14,
C15, C20
R15, R16
R17
1µF, 6.3V X5R ceramic capacitors
(0603)
Murata GRM188R60J105K
Taiyo Yuden JMK107BJ105KA
TDK C1608X5R1A105K
R18
R19, R20
C12, C13, C16
3
0.01Ω 1%, 0.5W 2010 sense resistor
Vishay Dale WSL2010 0.010 1.0%
IRC LRC-LR2010-01-R010-F
RS1
1
10A Schottky diode (D-PAK)
Diodes, Inc. MBRD1035CTL
ON Semiconductor MBRD1035CTL
D1 (optional)
D2
1
1
0.015Ω 1%, 0.5W 2010 sense
resistor
Vishay Dale WSL2010 0.015 1.0%
IRC LRC-LR2010-01-R015-F
RS2
U1
1
1
Schottky diode
Central Semiconductor
CMPSH1–4
MAX1908ETI or MAX8724ETI
Chip Information
TRANSISTOR COUNT: 3772
PROCESS: BiCMOS
26 ______________________________________________________________________________________
Low-Cost Multichemistry Battery Chargers
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
D2
0.15
C A
D
b
0.10 M
C A B
C
L
D2/2
D/2
k
PIN # 1
I.D.
0.15
C
B
PIN # 1 I.D.
0.35x45∞
E/2
E2/2
C
(NE-1) X
e
L
E2
E
k
L
DETAIL A
e
(ND-1) X
e
C
C
L
L
L
L
e
e
0.10
C
A
0.08
C
C
A3
A1
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE
16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0140
C
2
COMMON DIMENSIONS
EXPOSED PAD VARIATIONS
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1
SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE
ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220.
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
16, 20, 28, 32L, QFN THIN, 5x5x0.8 mm
APPROVAL
DOCUMENT CONTROL NO.
REV.
2
21-0140
C
2
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 ____________________ 27
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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