AAT2554 [ANALOGICTECH]
Total Power Solution for Portable Applications; 用于便携式应用的总电源解决方案型号: | AAT2554 |
厂家: | ADVANCED ANALOGIC TECHNOLOGIES |
描述: | Total Power Solution for Portable Applications |
文件: | 总33页 (文件大小:880K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
AAT2554
Total Power Solution for Portable Applications
™
SystemPower
General Description
Features
The AAT2554 is a fully integrated 500mA battery
charger, a 250mA step-down converter, and a
300mA low dropout (LDO) linear regulator. The
input voltage range is 4V to 6.5V for the battery
charger and 2.7V to 5.5V for the step-down con-
verter and linear regulator, making it ideal for
applications operating with single-cell lithium-
ion/polymer batteries.
•
Battery Charger:
— Input Voltage Range: 4V to 6.5V
— Programmable Charging Current up to
500mA
— Highly Integrated Battery Charger
•
•
Charging Device
Reverse Blocking Diode
•
Step-Down Converter:
— Input Voltage Range: 2.7V to 5.5V
— Output Voltage Range: 0.6V to VIN
— 250mA Output Current
The battery charger is a complete constant cur-
rent/constant voltage linear charger. It offers an
integrated pass device, reverse blocking protec-
tion, high accuracy current and voltage regulation,
charge status, and charge termination. The charg-
ing current is programmable via external resistor
from 15mA to 500mA. In addition to these stan-
dard features, the device offers over-voltage, cur-
rent limit, and thermal protection.
— Up to 96% Efficiency
— 30µA Quiescent Current
— 1.5MHz Switching Frequency
— 100µs Start-Up Time
Linear Regulator:
— 300mA Output Current
— Low Dropout: 400mV at 300mA
— Fast Line and Load Transient Response
— High Accuracy: ±1.5%
— 70µA Quiescent Current
Short-Circuit, Over-Temperature, and Current
Limit Protection
•
•
The step-down converter is a highly integrated
converter operating at a 1.5MHz switching fre-
quency, minimizing the size of external compo-
nents while keeping switching losses low. It has
independent input and enable pins. The output
voltage ranges from 0.6V to the input voltage.
•
•
TDFN34-16 Package
-40°C to +85°C Temperature Range
The AAT2554 linear regulator is designed for fast
transient response and good power supply ripple
rejection. Designed for 300mA of load current,
it includes short-circuit protection and thermal
shutdown.
Applications
The AAT2554 is available in a Pb-free, thermally-
enhanced TDFN34-16 package and is rated over
the -40°C to +85°C temperature range.
•
•
•
•
•
•
Bluetooth® Headsets
Cellular Phones
Handheld Instruments
MP3 and Portable Music Players
PDAs and Handheld Computers
Portable Media Players
Typical Application
Adapter/USB Input
VINB
ADP
ENB
STAT
VINA
EN_BAT
Enable
ENA
VOUTB
L= 3.0µH
AAT2554
BATT+
BATT-
LX
FB
BAT
RFB1
RFB2
COUTB
COUT
VOUTA
OUTA
ISET
RSET
COUTA
GND
Battery
Pack
2554.2007.01.1.2
1
AAT2554
Total Power Solution for Portable Applications
Pin Descriptions
Pin #
Symbol
Function
1
FB
Feedback input. This pin must be connected directly to an external resistor divider.
Nominal voltage is 0.6V.
2, 10, 12, 14
3
GND
ENB
Ground.
Enable pin for the step-down converter. When connected to logic low, the step-down
converter is disabled and consumes less than 1µA of current. When connected to
logic high, the converter resumes normal operation.
4
VINA
Linear regulator input voltage. Connect a 1µF or greater capacitor from this pin to
ground.
5
6
OUTA
Linear regulator output. Connect a 2.2µF capacitor from this pin to ground.
Enable pin for the battery charger. When connected to logic low, the battery charger
is disabled and consumes less than 1µA of current. When connected to logic high, the
charger resumes normal operation.
EN_BAT
7
ISET
Charge current set point. Connect a resistor from this pin to ground. Refer to typical
characteristics curves for resistor selection.
8
9
BAT
STAT
ADP
ENA
Battery charging and sensing.
Charge status input. Open drain status output.
11
13
Input for USB/adapter charger.
Enable pin for the linear regulator. When connected to logic low, the regulator is dis-
abled and consumes less than 1µA of current. When connected to logic high, it
resumes normal operation.
15
LX
Output of the step-down converter. Connect the inductor to this pin. Internally, it is
connected to the drain of both high- and low-side MOSFETs.
Input voltage for the step-down converter.
16
VINB
EP
Exposed paddle (bottom): connect to ground directly beneath the package.
Pin Configuration
TDFN34-16
(Top View)
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
VINB
LX
FB
GND
ENB
GND
ENA
GND
ADP
GND
STAT
VINA
OUTA
EN_BAT
ISET
BAT
2
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Absolute Maximum Ratings1
Symbol
Description
Value
Units
VINA, VINB
VADP
VLX
Input Voltage to GND
6.0
V
V
Adapter Voltage to GND
LX to GND
-0.3 to 7.5
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to 6.0
V
VFB
FB to GND
V
VEN
ENA, ENB, EN_BAT to GND
BAT, ISET, STAT
V
VX
-0.3 to VADP + 0.3
-40 to 150
V
TJ
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
°C
°C
TLEAD
300
Thermal Information
Symbol
Description
Value
Units
PD
Maximum Power Dissipation
Thermal Resistance2
2.0
50
W
θJA
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
2554.2007.01.1.2
3
AAT2554
Total Power Solution for Portable Applications
Electrical Characteristics1
VINB = 3.6V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
Conditions
Min
Typ
Max Units
Step-Down Converter
VIN
Input Voltage
2.7
5.5
2.7
V
V
VINB Rising
VUVLO
UVLO Threshold
Hysteresis
200
mV
V
VINB Falling
1.8
IOUTB = 0 to 250mA,
VINB = 2.7V to 5.5V
-3.0
3.0
VINB
1.0
%
VOUT
Output Voltage Tolerance2
VOUT
IQ
Output Voltage Range
Quiescent Current
0.6
V
µA
µA
mA
Ω
No Load
30
ISHDN
Shutdown Current
ENB = GND
ILIM
P-Channel Current Limit
High-Side Switch On Resistance
Low-Side Switch On Resistance
LX Leakage Current
600
0.59
0.42
RDS(ON)H
RDS(ON)L
ILXLEAK
Ω
VINB = 5.5V, VLX = 0 to VINB
VINB = 2.7V to 5.5V
1.0
µA
%/V
V
ΔVLinereg/ΔVIN Line Regulation
0.2
0.6
VFB
Feedback Threshold Voltage Accuracy VINB = 3.6V
0.591
0.609
0.2
IFB
FB Leakage Current
Oscillator Frequency
VOUTB = 1.0V
µA
MHz
FOSC
1.5
From Enable to Output
Regulation
TS
Startup Time
100
µs
TSD
THYS
VEN(L)
VEN(H)
IEN
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Enable Threshold Low
140
15
°C
°C
V
0.6
1.0
Enable Threshold High
1.4
V
Input Low Current
VINB = VENB = 5.5V
-1.0
µA
1. The AAT2554 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. Output voltage tolerance is independent of feedback resistor network accuracy.
4
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Electrical Characteristics1
VINA = VOUT(NOM) + 1V for VOUT options greater than 1.5V. IOUT = 1mA, COUT = 2.2µF, CIN = 1µF, TA = -40°C to
+85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
Conditions
Min Typ Max Units
Linear Regulator
I
OUTA = 1mA
TA = 25°C
-1.5
-2.5
1.5
2.5
VOUT Output Voltage Tolerance
%
to 300mA
TA = -40°C to +85°C
VOUT
VDO
+
2
VIN
Input Voltage
5.5
V
VDO
Dropout Voltage3
Line Regulation
IOUTA = 300mA
400
600
mV
%/V
ΔVOUT
VOUT*ΔVIN
/
VINA = VOUTA + 1 to 5.0V
OUTA = 300mA, VINA = VOUTA + 1
0.09
I
ΔVOUT(Line) Dynamic Line Regulation
2.5
60
mV
to VOUTA + 2, TR/TF = 2µs
IOUTA = 1mA to 300mA, TR <5µs
VOUTA > 1.2V
ΔVOUT(Load) Dynamic Load Regulation
mV
mA
mA
µA
IOUT
ISC
Output Current
300
Short-Circuit Current
Quiescent Current
Shutdown Current
VOUTA < 0.4V
600
70
IQ
VINA = 5V; ENA = VIN
VINA = 5V; ENA = 0V
1kHz
125
1.0
ISHDN
µA
65
45
43
Power Supply Rejection
Ratio
PSRR
TSD
IOUTA =10mA
10kHz
1MHz
dB
°C
Over-Temperature
Shutdown Threshold
Over-Temperature
Shutdown Hysteresis
Output Noise
145
THYS
eN
12
250
22
°C
µVRMS
ppm/°C
Output Voltage
TC
Temperature Coefficient
Enable Time Delay
Enable Threshold Low
Enable Threshold High
Enable Input Current
TEN DLY
15
µs
V
_
VEN(L)
VEN(H)
IEN
0.6
1.0
1.5
V
VENA = 5.5V
µA
1. The AAT2554 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
2. VDO is defined as VIN - VOUT when VOUT is 98% of nominal.
3. For VOUT <2.3V, VDO = 2.5V - VOUT
.
2554.2007.01.1.2
5
AAT2554
Total Power Solution for Portable Applications
Electrical Characteristics1
VADP = 5V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
Conditions
Min Typ Max Units
Battery Charger
Operation
VADP
Adapter Voltage Range
4.0
3
6.5
4
V
Under-Voltage Lockout (UVLO)
UVLO Hysteresis
Rising Edge
V
VUVLO
150
0.5
0.3
0.4
mV
mA
µA
µA
IOP
Operating Current
Charge Current = 200mA
1
1
2
ISHUTDOWN
ILEAKAGE
Voltage Regulation
Shutdown Current
VBAT = 4.25V, EN_BAT = GND
Reverse Leakage Current from BAT Pin VBAT = 4V, ADP Pin Open
VBAT EOC
End of Charge Accuracy
4.158 4.20 4.242
0.5
V
%
V
_
ΔVCH/VCH
VMIN
Output Charge Voltage Tolerance
Preconditioning Voltage Threshold
Battery Recharge Voltage Threshold
2.85
3.0
3.15
VRCH
Measured from VBAT EOC
-0.1
V
_
Current Regulation
ICH
ΔICH/ICH
VSET
Charge Current Programmable Range
15
500
mA
%
Charge Current Regulation Tolerance
ISET Pin Voltage
10
2
V
KI_A
Current Set Factor: ICH/ISET
800
Charging Devices
RDS(ON)
Charging Transistor On Resistance
VADP = 5.5V
0.9
1.1
Ω
Logic Control/Protection
VEN(H)
VEN(L)
Enable Threshold High
1.6
V
V
Enable Threshold Low
0.4
0.4
8
VSTAT
Output Low Voltage
STAT Pin Sinks 4mA
ICH = 100mA
V
ISTAT
STAT Pin Current Sink Capability
Over-Voltage Protection Threshold
Pre-Charge Current
mA
V
VOVP
4.4
10
10
ITK/ICHG
TERM/ICHG
%
%
I
Charge Termination Threshold Current
1. The AAT2554 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured
by design, characterization, and correlation with statistical process controls.
6
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Step-Down Converter
Efficiency vs. Load
(VOUT = 1.8V; L = 3.3µH)
DC Load Regulation
(VOUT = 1.8V; L = 3.3µH)
100
90
80
70
60
50
40
1.0
0.5
VIN = 5.0V
VIN = 2.7V
VIN = 3.6V
VIN = 3.6V
VIN = 5.5V
VIN = 5.5V
0.0
VIN = 2.7V
VIN = 4.2V
VIN = 5.0V
VIN = 4.2V
-0.5
-1.0
0.1
1
10
100
1000
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(VOUT = 1.2V; L = 1.5µH)
DC Load Regulation
(VOUT = 1.2V; L = 1.5µH)
100
90
80
70
60
50
40
30
1.0
0.5
VIN = 2.7V
VIN = 5.0V
VIN = 3.6V
VIN = 5.5V
0.0
VIN = 5.5V
VIN = 5.0V
VIN = 4.2V
VIN = 3.6V
VIN = 4.2V
-0.5
-1.0
VIN = 2.7V
0.1
1
10
100
1000
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Soft Start
(VIN = 3.6V; VOUT = 1.8V;
OUT = 250mA; CFF = 100pF)
Line Regulation
(VOUT = 1.8V)
I
0.6
5.0
4.0
3.0
2.0
1.0
0.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
0.5
0.4
VEN
IOUT = 0mA
IOUT = 50mA
0.3
0.2
IOUT = 150mA
0.1
-1.0
-2.0
-3.0
-4.0
-5.0
VO
0.0
-0.1
-0.2
-0.3
IOUT = 10mA
IOUT = 250mA
IL
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Time (100µs/div)
Input Voltage (V)
2554.2007.01.1.2
7
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Step-Down Converter
Output Voltage Error vs. Temperature
(VINB = 3.6V; VOUT = 1.8V; IOUT = 250mA)
Switching Frequency Variation
vs. Temperature
(VIN = 3.6V; VOUT = 1.8V)
3.0
2.0
10.0
8.0
6.0
1.0
4.0
2.0
0.0
0.0
-2.0
-4.0
-6.0
-8.0
-10.0
-1.0
-2.0
-3.0
-40
-20
0
20
40
60
80
100
5.5
6.0
-40
-20
0
20
40
60
80
100
Temperature (°C)
Temperature (°C)
Frequency Variation vs. Input Voltage
(VOUT = 1.8V)
No Load Quiescent Current vs. Input Voltage
50
45
40
2.0
1.0
0.0
85°C
35
-1.0
-2.0
-3.0
-4.0
30
25°C
25
-40°C
20
15
10
2.7
3.1
3.5
3.9
4.3
4.7
5.1
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
P-Channel RDS(ON) vs. Input Voltage
N-Channel RDS(ON) vs. Input Voltage
750
1000
900
800
700
600
500
400
300
700
650
600
550
500
450
400
350
300
120°C 100°C
85°C
120°C
100°C
85°C
25°C
25°C
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
Input Voltage (V)
8
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Step-Down Converter
Load Transient Response
(10mA to 250mA; VIN = 3.6V; VOUT = 1.8V;
Load Transient Response
(10mA to 250mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF)
C
OUT = 4.7µF; CFF = 100pF)
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
VO
VO
IO
IO
ILX
ILX
Time (25µs/div)
Time (25µs/div)
Line Response
(VOUT = 1.8V @ 250mA; CFF = 100pF)
Output Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA)
40
20
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0.00
-0.01
1.90
1.85
1.80
1.75
1.70
1.65
1.60
1.55
1.50
7.0
6.5
6.0
5.5
5.0
4.5
4.0
3.5
3.0
VO
VO
0
-20
-40
-60
-80
-100
-120
VIN
IL
Time (25µs/div)
Time (2µs/div)
Output Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 250mA)
40
20
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
VO
0
-20
-40
-60
-80
-100
-120
IL
Time (200ns/div)
2554.2007.01.1.2
9
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Battery Charger
Constant Charging Current
vs. Set Resistor Values
Charging Current vs. Battery Voltage
(VADP = 5V)
600
500
400
300
200
100
0
1000
100
10
RSET = 3.24kΩ
RSET = 5.36kΩ
RSET = 8.06kΩ
RSET = 31.6kΩ
RSET = 16.2kΩ
1
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
1
10
100
1000
VBAT (V)
RSET (kΩ)
End of Charge Battery Voltage
vs. Supply Voltage
End of Charge Voltage Regulation
vs. Temperature
(RSET = 8.06kΩ)
4.206
4.204
4.202
4.200
4.198
4.196
4.194
4.23
4.22
4.21
4.20
4.19
4.18
4.17
RSET = 8.06kΩ
RSET = 31.6kΩ
4.5
4.75
5
5.25
5.5
5.75
6
6.25
6.5
-50
-25
0
25
50
75
100
VADP (V)
Temperature (°C)
Constant Charging Current vs.
Supply Voltage
Constant Charging Current vs. Temperature
(RSET = 8.06kΩ)
(RSET = 8.06kΩ)
210
208
205
203
200
198
195
193
190
220
210
200
190
180
VBAT = 3.3V
VBAT = 4V
VBAT = 3.6V
170
4
-50
-25
0
25
50
75
100
4.25 4.5 4.75
5
5.25 5.5 5.75
6
6.25 6.5
VADP
(V)
Temperature (°C)
10
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Battery Charger
Operating Current vs. Temperature
(RSET = 8.06kΩΩ)
Preconditioning Threshold Voltage
vs. Temperature
(RSET = 8.06kΩ)
550
500
450
400
350
300
3.03
3.02
3.01
3
2.99
2.98
2.97
-50
-25
0
25
50
75
100
-50
-25
0
25
50
75
100
Temperature (°C)
Temperature (°C)
Preconditioning Charge Current
vs. Temperature
Preconditioning Charge Current
vs. Supply Voltage
(RSET = 8.06kΩΩ)
60
20.8
20.6
20.4
20.2
20.0
19.8
19.6
19.4
19.2
RSET = 3.24kΩ
50
40
30
20
10
0
RSET = 5.36kΩ
RSET = 8.06kΩ
RSET = 31.6kΩ
RSET = 16.2kΩ
4
4.2 4.4 4.6 4.8
5
5.2 5.4 5.6 5.8
6
6.2 6.4
-50
-25
0
25
50
75
100
Temperature (°C)
VADP (V)
Recharging Threshold Voltage
vs. Temperature
Sleep Mode Current vs. Supply Voltage
(RSET = 8.06kΩ)
(RSET = 8.06kΩΩ)
800
700
600
500
400
300
200
100
0
4.18
4.16
4.14
4.12
4.10
4.08
4.06
4.04
4.02
85°C
25°C
-40°C
-50
-25
0
25
50
75
100
4
4.25 4.5 4.75
5
5.25 5.5 5.75
6
6.25 6.5
Temperature (°C)
VADP (V)
2554.2007.01.1.2
11
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – Battery Charger
VEN(H) vs. Supply Voltage
(RSET = 8.06kΩΩ)
VEN(L) vs. Supply Voltage
(RSET = 8.06kΩ)
1.2
1.1
1
1.1
1
-40°C
-40°C
0.9
0.8
0.7
0.6
0.9
0.8
0.7
25°C
85°C
25°C
85°C
4
4.25 4.5 4.75
5
5.25 5.5 5.75
6
6.25 6.5
4
4.25 4.5
4.75
5
5.25 5.5
5.75
6
6.25 6.5
VADP (V)
VADP (V)
12
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – LDO Regulator
Dropout Voltage vs. Temperature
Dropout Characteristics
3.2
3.0
2.8
2.6
2.4
2.2
2.0
540
480
420
360
300
240
180
120
60
IL = 300mA
IOUT = 0mA
IOUT = 300mA
IL = 100mA
IL = 150mA
IOUT = 150mA
IOUT = 100mA
IOUT = 50mA
IOUT = 10mA
IL = 50mA
0
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90 100 110 120
2.7
2.8
2.9
3.0
3.1
3.2
3.3
Temperature (°C)
Input Voltage (V)
Ground Current vs. Input Voltage
Dropout Voltage vs. Output Current
90
500
450
400
350
300
250
200
150
100
50
80
70
60
50
40
30
20
10
0
IOUT = 300mA
85°C
IOUT = 150mA
IOUT = 50mA
25°C
IOUT = 0mA
IOUT = 10mA
-40°C
0
0
50
100
150
200
250
300
2
2.5
3
3.5
4
4.5
5
Input Voltage (V)
Output Current (mA)
Quiescent Current vs. Temperature
Output Voltage vs. Temperature
100
90
80
70
60
50
40
30
20
10
0
1.203
1.202
1.201
1.200
1.199
1.198
1.197
1.196
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90 100 110 120
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90 100
Temperature (°C)
Temperature (°C)
2554.2007.01.1.2
13
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – LDO Regulator
LDO Turn-On Time from Enable
(VIN Present)
LDO Initial Power-Up Response Time
6
5
4
3
2
1
0
4
3
2
1
0
7
6
5
4
3
2
1
0
6
5
4
3
2
1
0
Time (5µs/div)
Time (50µs/div)
Turn-Off Response Time
(I = 100mA)
Line Transient Response
6
5
4
3
2
1
0
3.04
3.03
3.02
3.01
3.00
2.99
2.98
VEN (5V/div)
VIN
VOUT
VOUT (1V/div)
Time (50µs/div)
Time (100µs/div)
Load Transient Response 300mA
Load Transient Response
2.90
2.85
2.80
2.75
2.70
2.65
2.60
500
400
300
200
100
0
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
800
700
600
500
400
300
200
100
0
VOUT
VOUT
IOUT
IOUT
-100
-100
Time (100µs/div)
Time (10µs/div)
14
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Typical Characteristics – LDO Regulator
Over-Current Protection
(EN = GND; ENLDO = VIN)
VEN(L) and VEN(H) vs. VIN
1200
1000
800
600
400
200
0
1.250
1.225
1.200
1.175
1.150
1.125
1.100
1.075
1.050
VEN(H)
VEN(L)
-200
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Time (50ms/div)
Input Voltage (V)
2554.2007.01.1.2
15
AAT2554
Total Power Solution for Portable Applications
Functional Block Diagram
Reverse Blocking
BAT
ADP
-
-
+
Constant
Current
Charge
Control
ISET
VREF
STAT
Over-
Temperature
Protection
UVLO
EN_BAT
VINB
DH
VINA
LX
Err.
Amp.
Logic
VREF
DL
Over-
Current
Protection
ENB
FB
-
+
VREF
OUTA
ENA
GND
Battery Charger
Functional Description
The battery charger is designed for single-cell lithi-
um-ion/polymer batteries using a constant current
and constant voltage algorithm. The battery charg-
er operates from the adapter/USB input voltage
range from 4V to 6.5V. The adapter/USB charging
current level can be programmed up to 500mA for
rapid charging applications. A status monitor out-
put pin is provided to indicate the battery charge
state by directly driving one external LED. Internal
device temperature and charging state are fully
monitored for fault conditions. In the event of an
over-voltage or over-temperature failure, the
device will automatically shut down, protecting the
charging device, control system, and the battery
under charge. Other features include an integrat-
ed reverse blocking diode and sense resistor.
The AAT2554 is a high performance power man-
agement IC comprised of a lithium-ion/polymer
battery charger, a step-down converter, and a lin-
ear regulator. The linear regulator is designed for
high-speed turn-on and fast transient response,
and good power supply ripple rejection. The step-
down converter operates in both fixed and variable
frequency modes for high efficiency performance.
The switching frequency is 1.5MHz, minimizing
the size of the inductor. In light load conditions,
the device enters power-saving mode; the switch-
ing frequency is reduced and the converter con-
sumes 30µA of current, making it ideal for battery-
operated applications.
16
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Switch-Mode Step-Down Converter
Under-Voltage Lockout
The step-down converter operates with an input
voltage of 2.7V to 5.5V. The switching frequency is
1.5MHz, minimizing the size of the inductor. Under
light load conditions, the device enters power-sav-
ing mode; the switching frequency is reduced, and
the converter consumes 30µA of current, making it
ideal for battery-operated applications. The output
voltage is programmable from VIN to as low as
0.6V. Power devices are sized for 250mA current
capability while maintaining over 90% efficiency at
full load. Light load efficiency is maintained at
greater than 80% down to 1mA of load current. A
high-DC gain error amplifier with internal compen-
sation controls the output. It provides excellent
transient response and load/line regulation.
The AAT2554 has internal circuits for UVLO and
power on reset features. If the ADP supply voltage
drops below the UVLO threshold, the battery
charger will suspend charging and shut down.
When power is reapplied to the ADP pin or the
UVLO condition recovers, the system charge con-
trol will automatically resume charging in the
appropriate mode for the condition of the battery. If
the input voltage of the step-down converter drops
below UVLO, the internal circuit will shut down.
Protection Circuitry
Over-Voltage Protection
An over-voltage protection event is defined as a
condition where the voltage on the BAT pin
exceeds the over-voltage protection threshold
(VOVP). If this over-voltage condition occurs, the
charger control circuitry will shut down the device.
The charger will resume normal charging operation
after the over-voltage condition is removed.
Linear Regulator
The advanced circuit design of the linear regulator
has been specifically optimized for very fast start-
up. This proprietary CMOS LDO has also been tai-
lored for superior transient response characteris-
tics. These traits are particularly important for appli-
cations that require fast power supply timing.
Current Limit, Over-Temperature Protection
For overload conditions, the peak input current is lim-
ited at the step-down converter. As load impedance
decreases and the output voltage falls closer to zero,
more power is dissipated internally, which causes the
internal die temperature to rise. In this case, the ther-
mal protection circuit completely disables switching,
which protects the device from damage.
The high-speed turn-on capability is enabled
through implementation of a fast-start control cir-
cuit which accelerates the power-up behavior of
fundamental control and feedback circuits within
the LDO regulator. The LDO regulator output has
been specifically optimized to function with low-
cost, low-ESR ceramic capacitors; however, the
design will allow for operation over a wide range
of capacitor types.
The battery charger has a thermal protection circuit
which will shut down charging functions when the
internal die temperature exceeds the preset ther-
mal limit threshold. Once the internal die tempera-
ture falls below the thermal limit, normal charging
operation will resume.
The regulator comes with complete short-circuit
and thermal protection. The combination of these
two internal protection circuits gives a comprehen-
sive safety system to guard against extreme
adverse operating conditions.
Control Loop
The AAT2554 contains a compact, current mode
step-down DC/DC controller. The current through
the P-channel MOSFET (high side) is sensed for
current loop control, as well as short-circuit and
overload protection. A fixed slope compensation
signal is added to the sensed current to maintain
stability for duty cycles greater than 50%. The peak
current mode loop appears as a voltage-pro-
grammed current source in parallel with the output
capacitor. The output of the voltage error amplifier
The regulator features an enable/disable function.
This pin (ENA) is active high and is compatible with
CMOS logic. To assure the LDO regulator will switch
on, the ENA turn-on control level must be greater
than 1.5V. The LDO regulator will go into the disable
shutdown mode when the voltage on the ENA pin
falls below 0.6V. If the enable function is not needed
in a specific application, it may be tied to VINA to
keep the LDO regulator in a continuously on state.
2554.2007.01.1.2
17
AAT2554
Total Power Solution for Portable Applications
programs the current mode loop for the necessary
charger begins constant-current charging. The cur-
rent level for this mode is programmed using a sin-
gle resistor from the ISET pin to ground.
Programmed current can be set from a minimum
15mA up to a maximum of 500mA. Constant cur-
rent charging will continue until the battery voltage
reaches the voltage regulation point, VBAT. When
the battery voltage reaches VBAT, the battery charg-
er begins constant voltage mode. The regulation
voltage is factory programmed to a nominal 4.2V
(±0.5%) and will continue charging until the charg-
ing current has reduced to 10% of the programmed
current.
peak switch current to force a constant output volt-
age for all load and line conditions. Internal loop
compensation terminates the transconductance
voltage error amplifier output. The error amplifier
reference is fixed at 0.6V.
Battery Charging Operation
Battery charging commences only after checking
several conditions in order to maintain a safe charg-
ing environment. The input supply (ADP) must be
above the minimum operating voltage (UVLO) and
the enable pin must be high (internally pulled down).
When the battery is connected to the BAT pin, the
charger checks the condition of the battery and
determines which charging mode to apply. If the bat-
tery voltage is below VMIN, the charger begins bat-
tery pre-conditioning by charging at 10% of the pro-
grammed constant current; e.g., if the programmed
current is 150mA, then the pre-conditioning current
(trickle charge) is 15mA. Pre-conditioning is purely a
safety precaution for a deeply discharged cell and
will also reduce the power dissipation in the internal
series pass MOSFET when the input-output voltage
differential is at its highest.
After the charge cycle is complete, the pass device
turns off and the device automatically goes into a
power-saving sleep mode. During this time, the
series pass device will block current in both direc-
tions, preventing the battery from discharging
through the IC.
The battery charger will remain in sleep mode,
even if the charger source is disconnected, until
one of the following events occurs: the battery ter-
minal voltage drops below the VRCH threshold; the
charger EN pin is recycled; or the charging source
is reconnected. In all cases, the charger will mon-
itor all parameters and resume charging in the
most appropriate mode.
Pre-conditioning continues until the battery voltage
reaches VMIN (see Figure 1). At this point, the
Preconditioning
Trickle Charge
Constant Current
Charge Phase
Constant Voltage
Charge Phase
Phase
Charge Complete Voltage
I = Max CC
Regulated Current
Constant Current Mode
Voltage Threshold
Trickle Charge and
I = CC / 10
Termination Threshold
Figure 1: Current vs. Voltage Profile During Charging Phases.
18
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Battery Charging System Operation Flow Chart
Enable
Power On Reset
No
Yes
Power Input
Voltage
VADP > VUVLO
Yes
Fault Conditions
Monitoring
OV, OT
Charge
Control
Shut Down
Yes
No
Preconditioning
Test
VMIN > VBAT
Preconditioning
(Trickle Charge)
Yes
No
No
Constant
Current Charge
Mode
Recharge Test
VRCH > VBAT
Current Phase Test
Yes
Yes
V
ADP > VBAT
No
Constant
Voltage Charge
Mode
Voltage Phase Test
IBAT > ITERM
Yes
No
Charge Completed
2554.2007.01.1.2
19
AAT2554
Total Power Solution for Portable Applications
le charge current, is dominated by the tolerance of
the set resistor used. For this reason, a 1% toler-
ance metal film resistor is recommended for the set
resistor function. Fast charge constant current lev-
els from 15mA to 500mA may be set by selecting
the appropriate resistor value from Table 1.
Application Information
Soft Start / Enable
The EN_BAT pin is internally pulled down. When
pulled to a logic high level, the battery charger is
enabled. When left open or pulled to a logic low level,
the battery charger is shut down and forced into the
sleep state. Charging will be halted regardless of the
battery voltage or charging state. When it is re-
enabled, the charge control circuit will automatically
reset and resume charging functions with the appro-
priate charging mode based on the battery charge
state and measured cell voltage from the BAT pin.
Normal
ICHARGE (mA)
Set Resistor
Ω
Value R1 (k )
500
400
300
250
200
150
100
50
3.24
4.12
5.36
6.49
8.06
10.7
16.2
31.6
38.3
53.6
78.7
105
Separate ENA and ENB inputs are provided to
independently enable and disable the LDO and
step-down converter, respectively. This allows
sequencing of the LDO and step-down outputs dur-
ing startup.
40
30
The LDO is enabled when the ENA pin is pulled
high. The control and feedback circuits have been
optimized for high-speed, monotonic turn-on char-
acteristics.
20
15
Table 1: RSET Values.
The step-down converter is enabled when the ENB
pin is pulled high. Soft start increases the inductor
current limit point in discrete steps when the input
voltage or ENB input is applied. It limits the current
surge seen at the input and eliminates output voltage
overshoot. When pulled low, the ENB input forces the
AAT2554 into a low-power, non-switching state. The
total input current during shutdown is less than 1µA.
1000
100
10
1
Adapter or USB Power Input
1
10
100
1000
Constant current charge levels up to 500mA may
be programmed by the user when powered from a
sufficient input power source. The battery charger
will operate from the adapter input over a 4.0V to
6.5V range. The constant current fast charge cur-
rent for the adapter input is set by the RSET resistor
connected between ISET and ground. Refer to
Table 1 for recommended RSET values for a desired
constant current charge level.
RSET (kΩ)
Figure 2: Constant Charging Current
vs. Set Resistor Values.
Charge Status Output
The AAT2554 provides battery charge status via a
status pin. This pin is internally connected to an N-
channel open drain MOSFET, which can be used to
drive an external LED. The status pin can indicate
several conditions, as shown in Table 2.
Programming Charge Current
The fast charge constant current charge level is
user programmed with a set resistor placed
between the ISET pin and ground. The accuracy of
the fast charge, as well as the preconditioning trick-
20
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
First, the maximum power dissipation for a given
situation should be calculated:
Event Description
Status
No battery charging activity
Battery charging via adapter
or USB port
OFF
ON
(TJ(MAX)
-
TA)
PD(MAX)
=
θJA
Charging completed
OFF
Where:
PD(MAX) = Maximum Power Dissipation (W)
θJA = Package Thermal Resistance (°C/W)
Table 2: LED Status Indicator.
The LED should be biased with as little current as
necessary to create reasonable illumination; there-
fore, a ballast resistor should be placed between
the LED cathode and the STAT pin. LED current
consumption will add to the overall thermal power
budget for the device package, hence it is good to
keep the LED drive current to a minimum. 2mA
should be sufficient to drive most low-cost green or
red LEDs. It is not recommended to exceed 8mA
for driving an individual status LED.
TJ(MAX) = Maximum Device Junction Temperature
(°C) [135°C]
TA
= Ambient Temperature (°C)
Figure 3 shows the relationship of maximum
power dissipation and ambient temperature of the
AAT2554.
The required ballast resistor values can be esti-
mated using the following formulas:
3000
2500
2000
1500
1000
500
(VADP
- VF(LED)
ILED
)
R1=
Example:
0
0
20
40
60
80
100
120
TA (°C)
(5.5V - 2.0V)
2mA
R1 =
= 1.75kΩ
Figure 3: Maximum Power Dissipation.
Next, the power dissipation of the battery charger
can be calculated by the following equation:
Note: Red LED forward voltage (VF) is typically
2.0V @ 2mA.
Thermal Considerations
PD = [(VADP - VBAT) · ICH + (VADP · IOP)]
The AAT2554 is offered in a TDFN34-16 package
which can provide up to 2W of power dissipation
when it is properly bonded to a printed circuit board
and has a maximum thermal resistance of 50°C/W.
Many considerations should be taken into account
when designing the printed circuit board layout, as
well as the placement of the charger IC package in
proximity to other heat generating devices in a given
application design. The ambient temperature around
the IC will also have an effect on the thermal limits of
a battery charging application. The maximum limits
that can be expected for a given ambient condition
can be estimated by the following discussion.
Where:
PD = Total Power Dissipation by the Device
VADP = ADP/USB Voltage
VBAT = Battery Voltage as Seen at the BAT Pin
ICH = Constant Charge Current Programmed for
the Application
IOP = Quiescent Current Consumed by the
Charger IC for Normal Operation [0.5mA]
2554.2007.01.1.2
21
AAT2554
Total Power Solution for Portable Applications
By substitution, we can derive the maximum
IQ is the step-down converter quiescent current.
The term tsw is used to estimate the full load step-
down converter switching losses.
charge current before reaching the thermal limit
condition (thermal cycling). The maximum charge
current is the key factor when designing battery
charger applications.
For the condition where the step-down converter is
in dropout at 100% duty cycle, the total device dis-
sipation reduces to:
(PD(MAX)
-
VIN
VIN - VBAT
· IOP)
ICH(MAX)
=
PTOTAL = IO2 · RDSON(H) + IQ · VIN
(TJ(MAX)
θJA
VIN - VBAT
- TA)
-
VIN · IOP
Since RDS(ON), quiescent current, and switching
losses all vary with input voltage, the total losses
should be investigated over the complete input
voltage range.
ICH(MAX)
=
In general, the worst condition is the greatest volt-
age drop across the IC, when battery voltage is
charged up to the preconditioning voltage thresh-
old. Figure 4 shows the maximum charge current in
different ambient temperatures.
Given the total losses, the maximum junction tem-
perature can be derived from the θJA for the
TDFN34-16 package which is 50°C/W.
TJ(MAX)
=
PTOTAL
·
Θ
JA + TAMB
500
400
TA = 60°C
300
Capacitor Selection
Linear Regulator Input Capacitor (C7)
TA = 85°C
200
An input capacitor greater than 1µF will offer supe-
rior input line transient response and maximize
power supply ripple rejection. Ceramic, tantalum,
or aluminum electrolytic capacitors may be select-
ed for CIN. There is no specific capacitor ESR
requirement for CIN. However, for 300mA LDO reg-
ulator output operation, ceramic capacitors are rec-
ommended for CIN due to their inherent capability
over tantalum capacitors to withstand input current
surges from low impedance sources such as bat-
teries in portable devices.
100
0
4.25 4.5 4.75
5
5.25 5.5 5.75
6
6.25 6.5 6.75
VIN (V)
Figure 4: Maximum Charging Current Before
Thermal Cycling Becomes Active.
There are three types of losses associated with the
step-down converter: switching losses, conduction
losses, and quiescent current losses. Conduction
losses are associated with the RDS(ON) characteris-
tics of the power output switching devices.
Switching losses are dominated by the gate charge
of the power output switching devices. At full load,
assuming continuous conduction mode (CCM), a
simplified form of the losses is given by:
Battery Charger Input Capacitor (C3)
In general, it is good design practice to place a
decoupling capacitor between the ADP pin and
GND. An input capacitor in the range of 1µF to
22µF is recommended. If the source supply is
unregulated, it may be necessary to increase the
capacitance to keep the input voltage above the
under-voltage lockout threshold during device
enable and when battery charging is initiated. If the
adapter input is to be used in a system with an
external power supply source, such as a typical
AC-to-DC wall adapter, then a CIN capacitor in the
range of 10µF should be used. A larger input
IO2 · (RDSON(H) · VO + RDSON(L) · [VIN - VO])
PTOTAL
=
VIN
+ (tsw · FS · IO + IQ) · VIN
22
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
capacitor in this application will minimize switching
or power transient effects when the power supply is
"hot plugged" in.
IO
2
IRMS(MAX)
=
VO
VIN
⎛
⎝
VO
VIN
⎞
⎠
·
1 -
Step-Down Converter Input Capacitor (C1)
Select a 4.7µF to 10µF X7R or X5R ceramic capac-
itor for the input. To estimate the required input
capacitor size, determine the acceptable input rip-
ple level (VPP) and solve for CIN. The calculated
value varies with input voltage and is a maximum
when VIN is double the output voltage.
The term
appears in both the input
voltage ripple and input capacitor RMS current
equations and is a maximum when VO is twice VIN.
This is why the input voltage ripple and the input
capacitor RMS current ripple are a maximum at
50% duty cycle.
The input capacitor provides a low impedance loop
for the edges of pulsed current drawn by the step-
down converter. Low ESR/ESL X7R and X5R
ceramic capacitors are ideal for this function. To
minimize stray inductance, the capacitor should be
placed as closely as possible to the IC. This keeps
the high frequency content of the input current
localized, minimizing EMI and input voltage ripple.
VO
VIN
⎛
· 1
⎝
VO
VIN
⎞
⎠
-
CIN =
⎛
⎝
VPP
IO
⎞
⎠
- ESR
·
FS
VO
VIN
⎛
VO
VIN
⎞
⎠
1
4
· 1
-
=
for VIN = 2 · VO
⎝
The proper placement of the input capacitor (C1)
can be seen in the evaluation board layout in
Figure 6.
1
CIN(MIN)
=
⎛
⎝
VPP
IO
⎞
⎠
A laboratory test set-up typically consists of two
long wires running from the bench power supply to
the evaluation board input voltage pins. The induc-
tance of these wires, along with the low-ESR
ceramic input capacitor, can create a high Q net-
work that may affect converter performance. This
problem often becomes apparent in the form of
excessive ringing in the output voltage during load
transients. Errors in the loop phase and gain meas-
urements can also result.
- ESR
·
4
·
FS
Always examine the ceramic capacitor DC voltage
coefficient characteristics when selecting the prop-
er value. For example, the capacitance of a 10µF,
6.3V, X5R ceramic capacitor with 5.0V DC applied
is actually about 6µF.
The maximum input capacitor RMS current is:
Since the inductance of a short PCB trace feeding
the input voltage is significantly lower than the
power leads from the bench power supply, most
applications do not exhibit this problem.
VO
VIN
⎛
· 1
⎝
VO
VIN
⎞
⎠
IRMS = IO
·
-
The input capacitor RMS ripple current varies with
the input and output voltage and will always be less
than or equal to half of the total DC load current.
In applications where the input power source lead
inductance cannot be reduced to a level that does
not affect the converter performance, a high ESR
tantalum or aluminum electrolytic capacitor should
be placed in parallel with the low ESR, ESL bypass
ceramic capacitor. This dampens the high Q net-
work and stabilizes the system.
VO
VIN
⎛
· 1
⎝
VO
VIN
⎞
⎠
1
2
-
=
D
· (1 - D) = 0.52 =
Linear Regulator Output Capacitor (C6)
for VIN = 2 · VO
For proper load voltage regulation and operational
stability, a capacitor is required between OUT and
GND. The COUT capacitor connection to the LDO
2554.2007.01.1.2
23
AAT2554
Total Power Solution for Portable Applications
regulator ground pin should be made as directly as
Once the average inductor current increases to the
DC load level, the output voltage recovers. The
above equation establishes a limit on the minimum
value for the output capacitor with respect to load
transients.
practically possible for maximum device perform-
ance. Since the regulator has been designed to
function with very low ESR capacitors, ceramic
capacitors in the 1.0µF to 10µF range are recom-
mended for best performance. Applications utilizing
the exceptionally low output noise and optimum
power supply ripple rejection should use 2.2µF or
greater for COUT. In low output current applications,
where output load is less than 10mA, the minimum
value for COUT can be as low as 0.47µF.
The internal voltage loop compensation also limits
the minimum output capacitor value to 4.7µF. This
is due to its effect on the loop crossover frequency
(bandwidth), phase margin, and gain margin.
Increased output capacitance will reduce the
crossover frequency with greater phase margin.
Battery Charger Output Capacitor (C5)
The maximum output capacitor RMS ripple current
is given by:
The AAT2554 only requires a 1µF ceramic capaci-
tor on the BAT pin to maintain circuit stability. This
value should be increased to 10µF or more if the
battery connection is made any distance from the
charger output. If the AAT2554 is to be used in
applications where the battery can be removed
from the charger, such as with desktop charging
cradles, an output capacitor greater than 10µF may
be required to prevent the device from cycling on
and off when no battery is present.
1
VOUT · (VIN(MAX) - VOUT)
IRMS(MAX)
=
·
L · FS · VIN(MAX)
2 · 3
Dissipation due to the RMS current in the ceram-
ic output capacitor ESR is typically minimal,
resulting in less than a few degrees rise in hot-
spot temperature.
Step-Down Converter Output Capacitor (C4)
The output capacitor limits the output ripple and
provides holdup during large load transitions. A
4.7µF to 10µF X5R or X7R ceramic capacitor typi-
cally provides sufficient bulk capacitance to stabi-
lize the output during large load transitions and has
the ESR and ESL characteristics necessary for low
output ripple. For enhanced transient response and
low temperature operation applications, a 10µF
(X5R, X7R) ceramic capacitor is recommended to
stabilize extreme pulsed load conditions.
Inductor Selection
The step-down converter uses peak current mode
control with slope compensation to maintain stabil-
ity for duty cycles greater than 50%. The output
inductor value must be selected so the inductor
current down slope meets the internal slope com-
pensation requirements. The internal slope com-
pensation for the AAT2554 is 0.45A/µsec. This
equates to a slope compensation that is 75% of the
inductor current down slope for a 1.8V output and
3.0µH inductor.
The output voltage droop due to a load transient is
dominated by the capacitance of the ceramic out-
put capacitor. During a step increase in load cur-
rent, the ceramic output capacitor alone supplies
the load current until the loop responds. Within two
or three switching cycles, the loop responds and
the inductor current increases to match the load
current demand. The relationship of the output volt-
age droop during the three switching cycles to the
output capacitance can be estimated by:
0.75 ⋅ VO 0.75 ⋅ 1.8V
= 0.45
A
µsec
m =
=
L
3.0µH
0.75 ⋅ VO
0.75
⋅
VO
A
µsec
⋅ VO
A
L =
=
≈
1.67
m
0.45A
µsec
3
·
VDROOP FS
ΔILOAD
COUT
=
·
24
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
For most designs, the step-down converter operates
Adjustable Output Resistor Selection
with inductor values from 1µH to 4.7µH. Table 3 dis-
plays inductor values for the AAT2554 for various
output voltages.
Resistors R2 and R3 of Figure 5 program the out-
put to regulate at a voltage higher than 0.6V. To
limit the bias current required for the external feed-
back resistor string while maintaining good noise
immunity, the suggested value for R3 is 59kΩ.
Decreased resistor values are necessary to main-
tain noise immunity on the FB pin, resulting in
increased quiescent current. Table 4 summarizes
the resistor values for various output voltages.
Manufacturer's specifications list both the inductor
DC current rating, which is a thermal limitation, and
the peak current rating, which is determined by the
saturation characteristics. The inductor should not
show any appreciable saturation under normal load
conditions. Some inductors may meet the peak and
average current ratings yet result in excessive loss-
es due to a high DCR. Always consider the losses
associated with the DCR and its effect on the total
converter efficiency when selecting an inductor.
V
V
3.3V
0.6V
⎛
⎝
⎞
⎛
⎝
⎞
- 1 ·
R2 =
OUT -1
·
R3 =
59kΩ = 267kΩ
⎠
⎠
REF
The 3.0µH CDRH2D09 series inductor selected
from Sumida has a 150mΩ DCR and a 470mA DC
current rating. At full load, the inductor DC loss is
9.375mW which gives a 2.08% loss in efficiency for
a 250mA, 1.8V output.
With enhanced transient response for extreme
pulsed load application, an external feed-forward
capacitor (C8 in Figure 5) can be added.
R3 = 59kΩ
R2 (kΩ)
R3 = 221kΩ
R2 (kΩ)
Output Voltage (V)
L1 (µH)
VOUT (V)
1.0
1.2
1.5
1.8
2.5
3.0
3.3
1.5
2.2
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
1.85
2.0
2.5
3.3
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
75
113
150
187
221
261
301
332
442
464
523
715
1000
2.7
3.0/3.3
3.9/4.2
4.7
5.6
Table 3: Step-Down Converter
Inductor Values.
124
137
187
267
Table 4: Adjustable Resistor Values For
Step-Down Converter.
2554.2007.01.1.2
25
AAT2554
Total Power Solution for Portable Applications
VINB
VINB
ADP
C1
4.7µF
U1
VBAT
ADP
16
11
9
8
1
2
VINB
BAT
OUTA
LX
5
VOUTA
L1
R4
1K
ADP
STAT
VINA
ENA
ENB
C3
4.7µF
VOUTA
VOUTB
C8
15
1
VOUTB
D1
4
FB
R2
118K
ENA
13
3
14
12
10
2
R5
100K
C4
4.7µF
GND
GND
VINB
VINA
100pF
C7
2.2µF
FB
JP2
6
C6
2.2µF
C5
2.2µF
R3
59K
R6
100K
JP3
C8 optional for
enhanced step-
down converter
transient
3
2
1
EN_BAT GND
ADP
7
ISET
GND
response
ENA
R7
100K
JP1
3
2
1
AAT2554
ENB
R1
8.06K
ENB
3
2
1
EN_BAT
GND
EN_BAT
Figure 5: AAT2554 Evaluation Board Schematic.
3. The feedback pin (Pin 1) should be separate
from any power trace and connect as closely as
possible to the load point. Sensing along a high-
current load trace will degrade DC load regula-
tion. Feedback resistors should be placed as
closely as possible to the FB pin (Pin 1) to mini-
mize the length of the high impedance feedback
trace. If possible, they should also be placed
away from the LX (switching node) and inductor
to improve noise immunity.
4. The resistance of the trace from the load return
GND (Pins 2, 10, 12, and 14) should be kept to
a minimum. This will help to minimize any error
in DC regulation due to differences in the poten-
tial of the internal signal ground and the power
ground.
Printed Circuit Board Layout
Considerations
For the best results, it is recommended to physi-
cally place the battery pack as close as possible to
the AAT2554 BAT pin. To minimize voltage drops
on the PCB, keep the high current carrying traces
adequately wide. Refer to the AAT2554 evaluation
board for a good layout example (see Figures 6
and 7). The following guidelines should be used to
help ensure a proper layout.
1. The input capacitors (C1, C3, C7) should con-
nect as closely as possible to ADP (Pin 11),
VINA (Pin 4), and VINB (Pin 16).
2. C4 and L1 should be connected as closely as
possible. The connection of L1 to the LX pin
should be as short as possible. Do not make the
node small by using narrow trace. The trace
should be kept wide, direct, and short.
5. A high density, small footprint layout can be
achieved using an inexpensive, miniature, non-
shielded, high DCR inductor.
26
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Figure 6: AAT2554 Evaluation Board
Top Side Layout.
Figure 7: AAT2554 Evaluation Board
Bottom Side Layout.
Component Part Number
Description
Manufacturer
U1
AAT2554IRN-T1
Total Power Solution for Portable Applications AnalogicTech
C1, C3, C4
GRM188R60J475KE19
GRM188R61A225KE34
CER 4.7µF 6.3V X5R 0603
CER 2.2µF 10V X5R 0603
Murata
C5, C6, C7
Murata
C8
GRM1886R1H101JZ01J CER 100pF 50V 5% R2H 0603
Murata
L1
R4
CDRH2D09-3R0
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
Shielded SMD, 3.0µH, 150mΩ, 3x3x1mm
1kΩ, 5%, 1/4W; 0603
8.06kΩ, 1%, 1/4W; 0603
118kΩ, 1%, 1/4W; 0603
59kΩ, 1%, 1/4W; 0603
100kΩ, 5%, 1/8W; 0402
Connecting Header, 2mm zip
Red LED; 1206
Sumida
Vishay
R1
Vishay
R2
Vishay
R3
Vishay
R5, R6, R7
Vishay
JP1, JP2, JP3 PRPN401PAEN
Sullins Electronics
Chicago Miniature Lamp
D1
CMD15-21SRC/TR8
Table 5: AAT2554 Evaluation Board Component Listing.
2554.2007.01.1.2
27
AAT2554
Total Power Solution for Portable Applications
Step-Down Converter Design Example
Specifications
VO
VIN
FS
= 1.8V @ 250mA, Pulsed Load ΔILOAD = 200mA
= 2.7V to 4.2V (3.6V nominal)
= 1.5MHz
TAMB = 85°C
1.8V Output Inductor
µsec
µsec
⋅ 1.8V = 3µH
A
L1 = 1.67
⋅ VO2 = 1.67
(use 3.0µH; see Table 3)
A
For Sumida inductor CDRH2D09-3R0, 3.0µH, DCR = 150mΩ.
⎛
⎞
⎠
VO
L1 ⋅ FS
VO
VIN
1.8
V
1.8V
4.2V
⎛
⎞
⎠
ΔIL1 =
⋅ 1 -
⎝
=
⋅ 1 -
= 228mA
⎝
3.0µH ⋅ 1.5MHz
ΔIL1
2
IPKL1 = IO +
= 250mA + 114mA = 364mA
2
PL1 = IO ⋅ DCR = 250mA2 ⋅ 150mΩ = 9.375mW
1.8V Output Capacitor
VDROOP = 0.1V
3 · ΔILOAD
VDROOP · FS
3 · 0.2A
COUT
=
=
= 4µF (use 4.7µF)
0.1V · 1.5MHz
(VO) · (VIN(MAX) - VO)
L1 · FS · VIN(MAX)
1
1.8V · (4.2V - 1.8V)
1
·
= 66mArms
IRMS
=
·
=
3.0µH · 1.5MHz · 4.2V
2· 3
2· 3
Pesr = esr · IRMS2 = 5mΩ · (66mA)2 = 21.8µW
28
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Input Capacitor
Input Ripple VPP = 25mV
1
1
CIN =
=
= 1.38µF (use 4.7µF)
⎛
⎝
VPP
IO
⎞
⎠
⎛
⎝
25mV
0.2A
⎞
- ESR
·
4
·
FS
- 5mΩ
· 4 · 1.5MHz
⎠
IO
IRMS
=
= 0.1Arms
2
P = esr
·
IRMS2 = 5mΩ
·
(0.1A)2 = 0.05mW
AAT2554 Losses
IO2 · (RDSON(H) · VO + RDSON(L) · [VIN -VO
]
)
PTOTAL
=
VIN
+ (tsw · FS · IO + IQ) · VIN
0.22 · (0.59
Ω
·
1.8V + 0.42Ω
4.2V
· [4.2V - 1.8V])
=
+ (5ns · 1.5MHz · 0.2A + 30µA) · 4.2V = 26.14mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 26.14mW = 86.3°C
2554.2007.01.1.2
29
AAT2554
Total Power Solution for Portable Applications
1
Ω
Ω
Output Voltage
VOUT (V)
R3 = 59k
R3 = 221k
Ω
Ω
R2 (k )
R2 (k )
L1 (µH)
0.6
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
1.85
2.0
2.5
3.3
0
0
1.5
1.5
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
75
113
150
187
221
261
301
332
442
464
523
715
1000
1.5
1.5
1.5
1.5
1.5
2.2
2.7
3.0/3.3
3.0/3.3
3.0/3.3
3.9/4.2
5.6
124
137
187
267
Table 6: Step-Down Converter Component Values.
Inductance
(µH)
Max DC
Current (mA)
DCR
(mΩ)
Size (mm)
LxWxH
Manufacturer
Part Number
Type
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Sumida
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
Taiyo Yuden
FDK
CDRH2D09-1R5
CDRH2D09-2R2
CDRH2D09-2R5
CDRH2D09-3R0
CDRH2D09-3R9
CDRH2D09-4R7
CDRH2D09-5R6
CDRH2D11-1R5
CDRH2D11-2R2
CDRH2D11-3R3
CDRH2D11-4R7
NR3010T1R5N
1.5
2.2
2.5
3.0
3.9
4.7
5.6
1.5
2.2
3.3
4.7
1.5
2.2
3.3
4.7
1.5
2.2
3.0
4.2
730
600
530
470
450
410
370
900
780
600
500
1200
1100
870
750
1200
1100
1000
900
110
144
150
194
225
287
325
68
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.2x3.2x1.2
3.2x3.2x1.2
3.2x3.2x1.2
3.2x3.2x1.2
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.0x3.0x1.0
3.2x2.6x0.8
3.2x2.6x0.8
3.2x2.6x0.8
3.2x2.6x0.8
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
98
Shielded
123
170
80
Shielded
Shielded
Shielded
NR3010T2R2M
NR3010T3R3M
NR3010T4R7M
MIPWT3226D-1R5
MIPWT3226D-2R2
MIPWT3226D-3R0
MIPWT3226D-4R2
95
Shielded
140
190
90
Shielded
Shielded
Chip shielded
Chip shielded
Chip shielded
Chip shielded
FDK
100
120
140
FDK
FDK
Table 7: Suggested Inductors and Suppliers.
1. For reduced quiescent current, R3 = 221kΩ.
30
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Value
(µF)
Voltage
Rating
Temp.
Co.
Case
Size
Manufacturer
Part Number
Murata
Murata
Murata
Murata
Murata
Murata
GRM21BR61A106KE19
GRM188R60J475KE19
GRM188R61A225KE34
GRM188R60J225KE19
GRM188R61A105KA61
GRM185R60J105KE26
10
4.7
2.2
2.2
1.0
1.0
10
6.3
10
X5R
X5R
X5R
X5R
X5R
X5R
0805
0603
0603
0603
0603
0603
6.3
10
6.3
Table 8: Surface Mount Capacitors.
2554.2007.01.1.2
31
AAT2554
Total Power Solution for Portable Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN34-16
TDFN34-16
TDFN34-16
TDFN34-16
RZXYY
VHXYY
SAXYY
TOXYY
AAT2554IRN-CAP-T1
AAT2554IRN-CAQ-T1
AAT2554IRN-CAT-T1
AAT2554IRN-CAW-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Legend
Voltage
Code
Adjustable
(0.6V)
0.9
A
B
E
G
I
1.2
1.5
1.8
1.9
Y
N
O
P
Q
R
S
T
2.5
2.6
2.7
2.8
2.85
2.9
3.0
3.3
W
C
4.2
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
32
2554.2007.01.1.2
AAT2554
Total Power Solution for Portable Applications
Package Information1
TDFN34-16
3.00 0.05
Detail "A"
Index Area
0.35 0.10
Top View
Bottom View
(4x)
Pin 1 Indicator
(optional)
0.05
0.229 0.051
0.05
Side View
Detail "A"
All dimensions in millimeters.
1. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the
lead terminals due to the manufacturing process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required
to ensure a proper bottom solder connection.
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights,
or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold sub-
ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. Testing and other quality con-
trol techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed.
AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are regis-
tered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
2554.2007.01.1.2
33
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