AAT2552_08 [ANALOGICTECH]
Total Power Solution for Portable Applications; 用于便携式应用的总电源解决方案
| 型号： | AAT2552_08 |
| 厂家： | 
ADVANCED ANALOGIC TECHNOLOGIES |
| 描述： | Total Power Solution for Portable Applications |
| 文件： | 总31页 (文件大小：824K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
General Description
Features
The AAT2552 is a fully integrated 500mA battery char-
ger, a 300mA step-down converter, and a 300mA low
dropout (LDO) linear regulator. The input voltage range
is 4V to 7.5V for the battery charger and 2.7V to 5.5V
for the step-down converter and linear regulator, making
it ideal for applications operating with single-cell lithium-
ion/polymer batteries.
• Battery Charger:
Input Voltage Range: 4V to 7.5V
Programmable Charging Current up to 500mA
Highly Integrated Battery Charger
▪
▪
▪
• Charging Device
• Reverse Blocking Diode
• Current Sensing
• Step-Down Converter:
The battery charger is a complete constant current/con-
stant voltage linear charger. It offers an integrated pass
device, reverse blocking protection, high accuracy cur-
rent and voltage regulation, charge status, and charge
termination. The charging current is programmable via
external resistor from 30mA to 500mA. In addition to
these standard features, the device offers over-voltage,
current limit, and thermal protection.
Input Voltage Range: 2.7V to 5.5V
Output Voltage Range: 0.6V to VIN
300mA Output Current
Up to 96% Efficiency
45μA Quiescent Current
1.5MHz Switching Frequency
120μs Start-Up Time
▪
▪
▪
▪
▪
▪
▪
• Linear Regulator:
The step-down converter is a highly integrated converter
operating at a 1.5MHz switching frequency, minimizing
the size of external components while keeping switching
losses low. The output voltage ranges from 0.6V to the
input voltage.
300mA Output Current
Low Dropout: 400mV at 300mA
Fast Line and Load Transient Response
High Accuracy: ±1.5%
▪
▪
▪
▪
85μA Quiescent Current
▪
• Short-Circuit, Over-Temperature, and Current Limit
Protection
• TDFN34-16 Package
The AAT2552 linear regulator is designed for high speed
turn-onandturn-offperformance,fasttransientresponse,
and good power supply ripple rejection. Delivering up to
300mA of load current, it includes short-circuit protec-
tion and thermal shutdown.
• -40°C to +85°C Temperature Range
Applications
• Bluetooth™ Headsets
• Cellular Phones
The AAT2552 is available in a Pb-free, thermally-
enhanced TDFN34-16 package and is rated over the
-40°C to +85°C temperature range.
• GPS
• Handheld Instruments
• MP3 and Portable Music Players
• PDAs and Handheld Computers
• Portable Media Players
Typical Application
Adapter/USB Input
Enable
INB
ENB
INA
ADP
STAT
EN_BAT
ENA
VOUTB
L1
LX
AAT2552
RFBB1
RFBB2
MODE
BAT
BATT+
BATT-
FBB
OUTA
COUTB
4.7μF
VOUTA
COUTA
RFBA1
RFBA2
COUT
ISET
FBA
GND
RSET
Battery
Pack
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2552.2008.02.1.2
1
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Pin Descriptions
Pin #
Symbol
Function
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 operates normally (pulled
down internally).
1
EN_BAT
Charge current set point. Connect a resistor from this pin to ground. Refer to typical characteristics
curves for resistor selection.
Analog ground.
Feedback input for the step-down converter. This pin must be connected directly to an external resistor
divider. Nominal voltage is 0.6V.
2
3
4
ISET
AGND
FBB
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 operates normally
(pulled up internally).
5
ENB
Pulled down internally for automatic PWM/LL operation. Connect to logic high for forced PWM. Drive with
external clock signal to synchronize step-down converter to external clock in PWM mode.
Enable pin for the linear regulator. When connected to logic low, the regulator is disabled and consumes
less than 1μA of current. When connected to logic high, the LDO operates normally (pulled up internally).
Feedback input for the LDO. This pin must be connected directly to an external resistor divider. Nominal
voltage is 1.24V.
6
7
8
MODE
ENA
FBA
9
10
11
OUTA
INA
INB
Linear regulator output. Connect a 2.2μF capacitor from this pin to ground.
Linear regulator input voltage. Connect a 1μF or greater capacitor from this pin to ground.
Input voltage for the step-down converter.
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.
12
LX
13
14
15
16
EP
PGND
BAT
ADP
Power ground.
Battery charging and sensing. Connect to positive terminal of Lithium-ion/polymer battery.
Input from USB port or AC wall adapter.
Open drain status pin for charger.
STAT
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
STAT
ADP
BAT
PGND
LX
INB
INA
EN_BAT
ISET
15
14
13
12
11
10
9
AGND
FBB
ENB
MODE
ENA
FBA
OUTA
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Absolute Maximum Ratings1
Symbol
Description
Value
Units
VINA, VINB
VADP
VLX
Input Voltage to GND
Adapter Voltage to GND
LX to GND
FB to GND
ENA, ENB, EN_BAT to GND
BAT, ISET, STAT
6.0
-0.3 to 7.5
V
V
V
V
V
V
°C
°C
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to 6.0
-0.3 to VADP + 0.3
-40 to 150
VFB
VEN
VX
TJ
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
TLEAD
300
Thermal Information
Symbol
Description
Value
Units
PD
θJA
Maximum Power Dissipation
Thermal Resistance2
2.0
50
W
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions 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.
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PRODUCT DATASHEET
AAT2552178
SystemPowerTM
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
7.5
2.6
V
V
mV
%
VINB Rising
Hysteresis
IOUTB = 0 to 300mA, VINB = 2.7V to 5.5V
VUVLO
UVLO Threshold
250
VOUT
VOUT
IQ
ISHDN
ILIM
RDS(ON)H
RDS(ON)L
ILXLEAK
Output Voltage Tolerance2
Output Voltage Range
Quiescent Current
-3.0
0.6
3.0
VINB
90
1.0
V
No Load
VENB = GND
45
μA
μA
mA
Ω
Ω
μA
%
Shutdown Current
P-Channel Current Limit
High-Side Switch On Resistance
Low-Side Switch On Resistance
LX Leakage Current
300
0.3
0.5
VINB = 5.5V, VLX = 0 to VINB
IOUTB = 0mA to 300mA
VINB = 2.7V to 5.5V
VINB = 3.6V
1.0
ΔVOUT/ΔVOUT Load Regulation
ΔVLinereg/ΔVIN Line Regulation
0.4
0.1
0.6
%/V
V
VFB
IFB
FOSC
TS
Feedback Threshold Voltage Accuracy
FB Leakage Current
Oscillator Frequency
Startup Time
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Enable Threshold Low
Enable Threshold High
Input Low Current
0.591
0.609
0.2
VOUTB = 1.0V
μA
MHz
μs
°C
°C
V
1.5
120
140
15
From Enable to Output Regulation
TSD
THYS
VEN(L)
VEN(H)
IEN
0.6
1.0
1.4
-1.0
V
μA
VINB = VENB = 5.5V
Linear Regulator
TA = 25°C
TA = -40°C to +85°C
-1.5
-2.5
1.5
2.5
IOUTA = 1mA
to 300mA
VOUT
Output Voltage Tolerance
%
VOUT
VFB
VIN
VDO
ΔVOUT
Output Voltage Range
Feedback Voltage Accuracy
Input Voltage
1.2
1.22
VOUT + VDO
3.3
1.26
5.5
V
V
V
1.24
400
3
Dropout Voltage4
IOUTA = 300mA; VOUT = 3.3V
VINA = VOUTA + 1 to 5.0V
650
mV
/
Line Regulation
0.09
%/V
VOUT*ΔVIN
IOUT
ISC
IQ
ISHDN
Output Current
VOUTA > 2.0V
VOUTA < 0.4V
VINA = 5V; VENA = VIN
VINA = 5V; VENA = 0V
1kHz
300
mA
mA
μA
Short-Circuit Current
Quiescent Current
Shutdown Current
400
85
150
1.0
μA
70
50
30
140
15
95
8
PSRR
Power Supply Rejection Ratio
IOUTA =10mA
10kHz
1MHz
dB
TSD
THYS
eN
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Output Noise
Output Voltage Temperature Coefficient
Enable Threshold Low
°C
°C
μVRMS/√Hz
ppm/°C
eNBW = 100Hz to 100kHz
TC
VEN(L)
VEN(H)
IEN
0.6
1.0
V
V
μA
Enable Threshold High
Enable Input Current
1.4
VINA = VENA = 5.5V
1. The AAT2552 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
2. Output voltage tolerance is independent of feedback resistor network accuracy.
3. VDO is defined as VIN - VOUT when VOUT is 98% of nominal.
4. For VOUT <2.3V, VDO = 2.5V - VOUT
.
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
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
Under-Voltage Lockout (UVLO)
UVLO Hysteresis
Operating Current
Shutdown Current
4.0
3
6.5
4
V
V
mV
mA
μA
μA
Rising Edge
VUVLO
150
0.5
0.3
0.4
IOP
ISHUTDOWN
ILEAKAGE
Charge Current = 200mA
VBAT = 4.25V, VEN_BAT = GND
VBAT = 4V, ADP Pin Open
1
1
2
Reverse Leakage Current from BAT Pin
Voltage Regulation
VBAT_EOC End of Charge Accuracy
VMIN
4.158
2.8
4.20
3.0
-0.1
4.242
3.2
V
V
V
Preconditioning Voltage Threshold
Battery Recharge Voltage Threshold
VRCH
Measured from VBAT_EOC
ICHARGE = 200mA
Current Regulation
ICH
ΔICH/ICH
VSET
Charge Current Programmable Range
Charge Current Regulation Tolerance
ISET Pin Voltage
30
-10
500
10
mA
%
V
2
KI_A
Current Set Factor: ICH/ISET
800
Charging Devices
Ω
RDS(ON)
Charging Transistor On Resistance
VADP = 5.5V
0.5
0.8
Logic Control/Protection
VEN(H)
VEN(L)
VSTAT
ISTAT
VOVP
Enable Threshold High
Enable Threshold Low
Output Low Voltage
STAT Pin Current Sink Capability
Over-Voltage Protection Threshold
Pre-Charge Current
1.6
V
V
V
mA
V
%
%
0.4
0.4
8
STAT Pin Sinks 4mA
ICH = 100mA
4.4
10
10
ITK/ICHG
ITERM/ICHG
Charge Termination Threshold Current
1. The AAT2552 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
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PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Battery Charger
Constant Charging Current vs. Set Resistors
(VIN = 5.0V)
Operating Supply Current vs. RSET
(VIN = 5.0V)
10000
1000
100
1000
100
10
Constant Current Mode
Preconditioning Mode
10
1
10
100
1000
1
10
100
RSET (kΩ)
RSET (kΩ)
Operating Current vs. Temperature
(VIN = 5.0V; RSET = 8.06kΩ)
Sleep Mode Current vs. Input Voltage
(RSET = 8.06kΩ)
540
520
500
480
460
440
800
700
600
500
400
300
200
100
0
25°C
85°C
-40°C
-50
-25
0
25
50
75
100
4.0
4.5
5.0
5.5
6.0
6.5
Temperature (°C)
Input Voltage (V)
Battery Charging Current vs. Battery Voltage
Constant Charging Current vs. Temperature
(RSET = 8.06kΩ)
600
215
210
205
200
195
190
185
RSET = 3.24K
500
400
RSET = 5.62K
300
RSET = 8.06K
200
RSET = 16.2K
RSET = 31.6K
100
0
-40
-15
10
35
60
85
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
VBAT (V)
Temperature (°C)
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Battery Charger
End of Charge Voltage Regulation
vs. Temperature
End of Charge Battery Voltage
vs. Input Voltage
(VIN = 5V; RSET = 8.06kΩ)
4.206
4.204
4.202
4.200
4.198
4.196
4.194
4.215
4.210
4.205
4.200
4.195
4.190
4.185
RSET = 8.06kΩ
RSET = 31.6kΩ
-40
-15
10
35
60
85
4.5
5
5.5
6
6.5
Temperature (°C)
VIN (V)
Recharging Threshold Voltage vs. Temperature
(RSET = 8.06kΩ)
Constant Charging Current vs. Input Voltage
(VIN = 5.62V)
4.16
4.14
4.12
4.10
4.08
4.06
4.04
310
VIN = 3.3V
305
300
295
290
285
VIN = 4V
VIN = 3.6V
-40
-15
10
35
60
85
4
4.5
5
5.5
6
6.5
VIN (V)
Temperature (°C)
Preconditioning Charge Current vs. Temperature
(RSET = 8.06kΩ)
Preconditioning Voltage Threshold vs. Temperature
(RSET = 8.06kΩ)
3.03
3.02
3.01
3.00
2.99
2.98
2.97
20.8
20.4
20.0
19.6
19.2
-40
-15
10
35
60
85
-40
-15
10
35
60
85
Temperature (°C)
Temperature (°C)
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PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Battery Charger
Enable Threshold High vs. Input Voltage
(RSET = 8.06kΩ)
Enable Threshold Low vs. Input Voltage
(RSET = 8.06kΩ)
1.1
1.0
0.9
0.8
0.7
0.6
1.2
-40°C
1.1
-40°C
1.0
0.9
85°C
85°C
0.8
25°C
25°C
0.7
4.0
4.5
5.0
5.5
6.0
6.5
4.0
4.5
5.0
5.5
6.0
6.5
V
IN (V)
VIN (V)
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Step-Down Converter
Efficiency vs. Load
(VOUT = 3.3V; L = 5.6µH)
DC Regulation
(VOUT = 3.3V; L = 5.6µH)
100
90
80
70
60
50
40
1.0
0.5
VIN = 3.6V
VIN = 5.0V
VIN = 5.0V
VIN = 4.2V
0.0
VIN = 4.2V
-0.5
-1.0
VIN = 3.6V
0.1
1
10
100
1000
1000
1000
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(VOUT = 1.8V; L = 3.3µH)
DC Regulation
(VOUT = 1.2V; L = 1.5μH)
100
90
80
70
60
50
40
1.0
0.5
VIN = 3.6V
VIN = 2.7V
VIN = 3.6V
VIN = 5.0V
VIN = 5.0V
VIN = 4.2V
0.0
VIN = 2.7V
VIN = 4.2V
-0.5
-1.0
0.1
1
10
100
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(VOUT = 1.2V; L = 1.5µH)
DC Regulation
(VOUT = 1.2V; L = 1.5μH)
100
90
80
70
60
50
40
1.0
0.5
VIN = 3.6V
VIN = 3.6V
VIN = 5.0V
VIN = 2.7V
0.0
VIN = 5.0V
VIN = 2.7V
VIN = 4.2V
VIN = 4.2V
-0.5
-1.0
0.1
1
10
100
1000
0.1
1
10
100
Output Current (mA)
Output Current (mA)
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2552.2008.02.1.2
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PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Step-Down Converter
Line Regulation
(VOUT = 1.8V)
Soft Start
(VIN = 3.6V; VOUT = 1.8V; IOUT = 150mA)
4
3
2
1
0
0.2
VEN
IOUT = 10mA
0.1
0
VOUT
IOUT = 50mA
-0.1
-0.2
-0.3
-0.4
IL
0.3
0.2
0.1
0.0
IOUT = 150mA
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Time (100µs/div)
Output Voltage Accuracy vs. Temperature
(VIN = 3.6V; VO = 1.8V; IOUT = 150mA)
No Load Quiescent Current vs. Input Voltage
2.0
70
1.5
1.0
85°C
25°C
60
50
40
30
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-40°C
-40
-15
10
35
60
85
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Temperature (°C)
N-Channel RDS(ON) vs. Input Voltage
P-Channel RDS(ON) vs. Input Voltage
600
500
400
300
200
100
1000
900
800
700
600
500
400
300
85°C
85°C
100°C
120°C
100°C
120°C
25°C
25°C
2.5
3
3.5
4
4.5
5
5.5
6
2.5
3
3.5
4
4.5
5
5.5
6
VIN (V)
VIN (V)
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–Step-Down Converter
Load Transient Response
(10mA to 300mA; VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF; C = 100pF)
Line Transient Response
(VOUT = 1.8V @ 150mA, CFF = 100pF)
2.0
1.9
1.8
1.7
1.6
1.90
1.85
1.80
1.75
VOUT
IOUT
300mA
10mA
4.6
4.1
3.6
3.1
0.2
0.0
-0.2
ILX
Time (20µs/div)
Time (25µs/div)
Output Voltage Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 300mA)
Output Voltage Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA)
40
20
0
1.81
1.80
1.79
-20
0.4
0.05
0.3
0.2
0.1
0.00
-0.05
-0.10
Time (0.2µs/div)
Time (5µs/div)
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2552.2008.02.1.2
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PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–LDO Regulator
Quiescent Current vs. Temperature
(VIN = 5V)
Dropout Voltage vs. Temperature
0.5
0.4
0.3
0.2
0.1
0.0
120
110
100
90
IL = 300mA
IL = 200mA
IL = 100mA
IL = 50mA
80
70
60
50
-40
-20
0
20
40
60
80
100
120
-40
-15
10
35
60
85
Temperature (°C)
Temperature (°C)
LDO Dropout Characteristics
(EN = GND; ENLDO = VIN)
Dropout Voltage vs. Output Current
0.5
0.4
0.3
0.2
0.1
0.0
3.20
85°C
25°C
3.00
2.80
2.60
2.40
2.20
2.00
IOUT = 0mA
IOUT = 300mA
IOUT = 150mA
IOUT = 100mA
IOUT = 50mA
-40°C
IOUT = 10mA
2.80
0
50
100
150
200
250
300
2.70
2.90
3.00
3.10
3.20
3.30
Output Current (mA)
Input Voltage (V)
Output Voltage vs. Temperature
(VIN = 3.6V; VO = 1.8V; IOUT = 150mA)
Enable Threshold Voltage vs. Input Voltage
3.301
3.300
3.299
3.298
3.297
3.296
0.96
0.94
VEN(H)
0.92
0.9
0.88
0.86
VEN(L)
0.84
0.82
-40
-15
10
35
60
85
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Temperature (°C)
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Typical Characteristics–LDO Regulator
Line Transient Response
(IOUT = 300mA)
Load Transient Response
(1mA to 300mA; VIN = 5.0V; VOUT = 3.3V)
3.40
3.6
3.4
3.2
3.35
VOUT
VOUT
3.30
5.0
4.5
VIN
0.4
0.2
0.0
-0.2
4.0
IL
Time (100µs/div)
Time (100µs/div)
Turn-Off Response Time
(VIN = 4.2V; IOUT = 300mA)
Turn-On Time From Enable
(VIN = 4.2V; IOUT = 300mA)
VEN = 2V/div
VEN = 2V/div
VOUT = 1V/div
VOUT = 1V/div
Time (50µs/div)
Time (100µs/div)
LDO Output Noise
(COUT = 4.7µF; IOUT = 10mA; RLOAD = 330; 98.33µVrms)
10000
1000
100
10
0.01
0.1
1
10
100
1000
Frequency (kHz)
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2552.2008.02.1.2
13
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Functional Block Diagram
Reverse Blocking
ADP
BAT
Current Compare
CV/Pre-Charge
Charge
Control
Constant Current
ISET
UVLO
STAT
FBB
INB
Charge Status
EN_BAT
Err.
Amp
.
DH
LX
Voltage
Reference
Logic
DL
ENB
Input
MODE
PGND
OUTA
Over-Temperature
Protection
From
Charger Section
INA
Active Feedback
Control
Over-Current
Protection
Err.+
FBA
Amp
Voltage
Reference
Fast Start
Control
-
ENA
AGND
adapter/USB input voltage range from 4V to 7.5V. The
adapter/USB charging current level can be programmed
up to 500mA for rapid charging applications. A status
monitor output 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
integrated reverse blocking diode and sense resistor.
Functional Description
The AAT2552 is a high performance power man-agement
IC comprised of a lithium-ion/polymer battery charger, a
step-down converter, and a linear regulator. The linear
regulator is designed for high-speed turn-on and fast
transient response, and good power supply ripple rejec-
tion. 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 switching frequency is reduced
and the converter consumes 45μA of current, making it
ideal for battery-operated applications.
Switch-Mode Step-Down Converter
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-saving mode; the
switching frequency is reduced, and the converter con-
Battery Charger
The battery charger is designed for single-cell lithium-ion/
polymer batteries using a constant current and constant
voltage algorithm. The battery charger operates from the
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14
2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
sumes 45μA of current, making it ideal for battery-
operated applications. The output voltage is program-
mable from VIN to as low as 0.6V. Power devices are
sized for 300mA current capability while maintaining
over 96% 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
compensation controls the output. It provides excellent
transient response and load/line regulation.
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-volt-
age protection threshold (VOVP). If this over-voltage condi-
tion occurs, the charger control circuitry will shut down
the device. The charger will resume normal charging
operation after the over-voltage condition is removed.
The AAT2552 synchronous step-down converter can be
synchronized to an external clock signal applied to the
MODE pin.
Linear Regulator
Current Limit / Over-Temperature Protection
The advanced circuit design of the linear regulator has
been specifically optimized for very fast start-up. This
proprietary CMOS LDO has also been tailored for supe-
rior transient response characteristics. These traits are
particularly important for applications that require fast
power supply timing.
For overload conditions, the peak input current is limited
at the step-down converter. As load impedance decreas-
es 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 thermal protec-
tion 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 circuit which
accelerates the power-up behavior of fundamental con-
trol 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 thermal limit threshold.
Once the internal die temperature falls below the thermal
limit, normal charging operation will resume.
Control Loop
The regulator comes with complete short-circuit and ther-
mal protection. The combination of these two internal
protection circuits gives a comprehensive safety system
to guard against extreme adverse operating conditions.
The AAT2552 contains a compact, current mode step-
downDC/DCcontroller.ThecurrentthroughtheP-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 cur-
rent to maintain stability for duty cycles greater than
50%. The peak current mode loop appears as a voltage-
programmed current source in parallel with the output
capacitor. The output of the voltage error amplifier pro-
grams the current mode loop for the necessary peak
switch current to force a constant output voltage 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.
The regulator features an enable/disable function. This
pin (ENA) is active high and is compatible with CMOS
logic. The LDO regulator will go into the disable shut-
down 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 INA to keep the LDO regu-
lator in a continuously on state.
Under-Voltage Lockout
The AAT2552 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 control will automatically resume charging in the
Battery Charging Operation
Battery charging commences only after checking several
conditions in order to maintain a safe charging environ-
ment. The input supply (ADP) must be above the mini-
mum operating voltage (UVLO) and the enable pin must
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2552.2008.02.1.2
15
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
be high (internally pulled down). When the battery is
connected to the BAT pin, the charger checks the condi-
tion of the battery and determines which charging mode
to apply. If the battery voltage is below VMIN, the charger
begins battery pre-conditioning by charging at 10% of
the programmed constant current; e.g., if the pro-
grammed 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 dif-
ferential is at its highest.
voltage reaches the voltage regulation point, VBAT. When
the battery voltage reaches VBAT, the battery charger
begins constant voltage mode. The regulation voltage is
factory programmed to a nominal 4.2V (±0.5%) and will
continue charging until the charging current has reduced
to 10% of the programmed current.
After the charge cycle is complete, the pass device turns
off and the device automatically goes into a power-sav-
ing sleep mode. During this time, the series pass device
will block current in both directions, preventing the bat-
tery from discharging through the IC.
The battery charger will remain in sleep mode, even if
the charger source is disconnected, until one of the fol-
lowing events occurs: the battery terminal voltage drops
below the VRCH threshold; the charger EN pin is recycled;
or the charging source is reconnected. In all cases, the
charger will monitor 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 charger
begins constant-current charging. The current level for
this mode is programmed using a single resistor from
the ISET pin to ground. Programmed current can be set
from a minimum 15mA up to a maximum of 500mA.
Constant current charging will continue until the battery
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
Constant Voltage
Charge Phase
Charge Complete Voltage
Regulated Current
I = Max CC
Constant Current Mode
Voltage Threshold
Trickle Charge and
Termination Threshold
I = CC / 10
Figure 1: Current vs. Voltage Profile During Charging Phases.
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
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
Preconditioning
(Trickle Charge)
Yes
V
MIN > VBAT
No
No
Constant
Current Charge
Mode
Recharge Test
Current Phase Test
BAT_EOC > VBAT
Yes
Yes
V
RCH > VBAT
V
No
Constant
Voltage Charge
Mode
Voltage Phase Test
IBAT > ITERM
Yes
No
Charge Completed
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2552.2008.02.1.2
17
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
stant current levels from 30mA to 500mA may be set by
selecting the appropriate resistor value from Table 1.
Application Information
Soft Start / Enable
Normal ICHARGE (mA) Set Resistor Value R1 (kΩ)
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 charg-
ing functions with the appropriate charging mode based
on the battery charge state and measured cell voltage
from the BAT pin.
500
400
300
250
200
150
100
50
40
30
20
15
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 indepen-
dently enable and disable the LDO and step-down con-
verter, respectively. This allows sequencing of the LDO
and step-down outputs during startup.
Table 1: RSET Values.
1000
100
10
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 characteristics.
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 AAT2552 into
a low-power, non-switching state. The step-down con-
verter input current during shutdown is less than 1μA.
1
1
10
100
1000
RSET (kΩ)
Figure 2: Constant Charging Current
vs. Set Resistor Values.
Adapter or USB Power Input
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 7.5V range. The
constant current fast charge current for the adapter
input is set by the RSET resistor connected between ISET
and ground. Refer to Table 1 for recommended RSET val-
ues for a desired constant current charge level.
Charge Status Output
The AAT2552 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 exter-
nal LED. The status pin can indicate several conditions,
as shown in Table 2.
Event Description
Status
Programming Charge Current
No battery charging activity
Battery charging via adapter or USB port
Charging completed
OFF
ON
OFF
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 trickle charge current, is domi-
nated by the tolerance of the set resistor used. For this
reason, a 1% tolerance metal film resistor is recom-
mended for the set resistor function. Fast charge con-
Table 2: LED Status Indicator.
The LED should be biased with as little current as neces-
sary to create reasonable illumination; therefore, a bal-
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
last 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 pack-
age, 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.
Figure 3 shows the relationship of maximum power dis-
sipation and ambient temperature of the AAT2552.
3.00
2.50
2.00
1.50
1.00
0.50
0.00
The required ballast resistor values can be estimated
using the following formulas:
(VADP
- VF(LED)
ILED
)
R6 =
0
20
40
60
80
100
TA (°°C)
Example:
Figure 3: Maximum Power Dissipation.
(5.5V - 2.0V)
2mA
R6 =
= 1.75kΩ
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.
PD = [(VADP - VBAT) · ICH + (VADP · IOP)]
Thermal Considerations
Where:
The AAT2552 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 consider-
ations 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 gen-
erating devices in a given application design. The ambi-
ent 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 dis-
cussion.
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]
By substitution, we can derive the maximum charge cur-
rent before reaching the thermal limit condition (thermal
cycling). The maximum charge current is the key factor
when designing battery charger applications.
(PD(MAX)
-
VIN
VIN - VBAT
· IOP)
First, the maximum power dissipation for a given situa-
tion should be calculated:
ICH(MAX)
=
(TJ(MAX) TA)
θJA
VIN - VBAT
-
-
VIN · IOP
(TJ(MAX) - TA)
θJA
PD(MAX)
=
ICH(MAX)
=
In general, the worst condition is the greatest voltage
drop across the IC, when battery voltage is charged up
to the preconditioning voltage threshold. Figure 4 shows
the maximum charge current in different ambient tem-
peratures.
Where:
PD(MAX) = Maximum Power Dissipation (W)
θJA = Package Thermal Resistance (°C/W)
TJ(MAX) = Maximum Device Junction Temperature (°C)
[135°C]
TA
= Ambient Temperature (°C)
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2552.2008.02.1.2
19
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Capacitor Selection
500
450
400
350
300
250
200
150
TA = 25°C
Linear Regulator Input Capacitor (C6)
An input capacitor greater than 1μF will offer superior
input line transient response and maximize power sup-
ply ripple rejection. Ceramic, tantalum, or aluminum
electrolytic capacitors may be selected for CIN. There is
no specific capacitor ESR requirement for CIN. However,
for 300mA LDO regulator output operation, ceramic
capacitors are recommended for CIN due to their inher-
ent capability over tantalum capacitors to withstand
input current surges from low impedance sources such
as batteries in portable devices.
TA = 60°C
TA = 45°C
TA = 85°C
100
50
0
4.25 4.5 4.75
5
5.25 5.5 5.75
6
6.25 6.5 6.75
7
VIN (V)
Figure 4: Maximum Charging Current Before
Thermal Cycling Becomes Active.
Battery Charger Input Capacitor (C1)
In general, it is good design practice to place a decou-
pling 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 capacitor in this application will
minimize switching or power transient effects when the
power supply is “hot plugged” in.
There are three types of losses associated with the step-
down converter: switching losses, conduction losses, and
quiescent current losses. Conduction losses are associ-
ated with the RDS(ON) characteristics 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:
IO2 · (RDSON(H) · VO + RDSON(L) · [VIN - VO])
PTOTAL
=
VIN
Step-Down Converter Input Capacitor (C6)
+ (tsw · FS · IO + IQ) · VIN
Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for
the input. To estimate the required input capacitor size,
determine the acceptable input ripple level (VPP) and solve
for CIN. The calculated value varies with input voltage and
is a maximum when VIN is double the output voltage.
IQ is the step-down converter quiescent current. The
term tsw is used to estimate the full load step-down con-
verter switching losses.
For the condition where the step-down converter is in
dropout at 100% duty cycle, the total device dissipation
reduces to:
VO
VIN
⎛
VO ⎞
VIN ⎠
· 1 -
⎝
CIN =
⎛ VPP
⎝ IO
⎞
PTOTAL = IO2 · RDSON(H) + IQ · VIN
- ESR ·FS
⎠
VO
VIN
⎛
VO ⎞
1
Since RDS(ON), quiescent current, and switching losses all
vary with input voltage, the total losses should be inves-
tigated over the complete input voltage range.
· 1 -
=
for VIN = 2 · VO
⎝
VIN ⎠
4
1
CIN(MIN)
=
Given the total losses, the maximum junction tempera-
ture can be derived from the θJA for the TDFN34-16
package which is 50°C/W.
⎛ VPP
⎝ IO
⎞
⎠
- ESR · 4 · FS
Always examine the ceramic capacitor DC voltage coeffi-
cient characteristics when selecting the proper value. For
example, the capacitance of a 10μF, 6.3V, X5R ceramic
capacitor with 5.0V DC applied is actually about 6μF.
TJ(MAX) = PTOTAL · ΘJA + TAMB
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
The maximum input capacitor RMS current is:
the converter performance, a high ESR tantalum or alu-
minum electrolytic capacitor should be placed in parallel
with the low ESR, ESL bypass ceramic capacitor. This
dampens the high Q network and stabilizes the system.
The linear regulator and the step-down convertor share
the same input capacitor on the evaluation board.
VO
VIN
⎛
VO ⎞
VIN ⎠
1
2
· 1 -
⎝
=
D · (1 - D) = 0.52 =
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.
Linear Regulator Output Capacitor (C5)
For proper load voltage regulation and operational stabil-
ity, a capacitor is required between OUT and GND. The
COUT capacitor connection to the LDO regulator ground
pin should be made as directly as practically possible for
maximum device performance. Since the regulator has
been designed to function with very low ESR capacitors,
ceramic capacitors in the 1.0μF to 10μF range are rec-
ommended for best performance. Applications utilizing
the exceptionally low output noise and optimum power
supply ripple rejection should use 2.2μF or greater for
VO
VIN
⎛
VO ⎞
VIN ⎠
IRMS = IO ·
· 1 -
⎝
for VIN = 2 · VO
IO
IRMS(MAX)
=
2
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 term appears in both the input voltage ripple and
input capacitor RMS current equations and is a maxi-
mum 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.
Battery Charger Output Capacitor (C2)
The battery charger of the AAT2552 only requires a 1μF
ceramic capacitor on the BAT pin to maintain circuit stabil-
ity. This value should be increased to 10μF or more if the
battery connection is made any distance from the charger
output. If the AAT2552 is to be used in applications where
the battery can be removed from the charger, such as
with desktop charging cradles, an output capacitor great-
er than 10μF may be required to prevent the device from
cycling on and off when no battery is present.
The input capacitor provides a low impedance loop for the
edges of pulsed current drawn by the step-down con-
verter. 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.
The proper placement of the input capacitor (C6) can be
seen in the evaluation board layout in Figure 7.
Step-Down Converter Output Capacitor (C3)
The output capacitor limits the output ripple and pro-
vides holdup during large load transitions. A 4.7μF to
10μF X5R or X7R ceramic capacitor typically provides
sufficient bulk capacitance to stabilize the output during
large load transitions and has the ESR and ESL charac-
teristics necessary for low output ripple. For enhanced
transient response and low temperature operation appli-
cations, a 10μF (X5R, X7R) ceramic capacitor is recom-
mended to stabilize extreme pulsed load conditions.
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the evalu-
ation board input voltage pins. The inductance of these
wires, along with the low-ESR ceramic input capacitor,
can create a high Q network that may affect converter
performance. This problem often becomes apparent in
the form of excessive ringing in the output voltage dur-
ing load transients. Errors in the loop phase and gain
measurements can also result.
The output voltage droop due to a load transient is dom-
inated by the capacitance of the ceramic output capacitor.
During a step increase in load current, 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-
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.
In applications where the input power source lead induc-
tance cannot be reduced to a level that does not affect
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2552.2008.02.1.2
21
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
age droop during the three switching cycles to the output
capacitance can be estimated by:
peak current rating, which is determined by the satura-
tion 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 losses 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.
3 · ΔILOAD
=
COUT
V
DROOP · FS
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equa-
tion establishes a limit on the minimum value for the
output capacitor with respect to load transients.
The 3.0μH CDRH2D09 series inductor selected from
Sumida has a 150mΩ DCR and a 470mA DC current rat-
ing. At full load, the inductor DC loss is 9.375mW which
gives a 2.08% loss in efficiency for a 250mA, 1.8V out-
put.
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 capac-
itance will reduce the crossover frequency with greater
phase margin.
Adjustable Output Voltage
for the Step-down Converter
The maximum output capacitor RMS ripple current is
given by:
Resistors R2 and R3 of Figure 5 program the output of
the step down converter and regulate at a voltage high-
er than 0.6V. To limit the bias current required for the
external feedback resistor string while maintaining good
noise immunity, the suggested value for R3 is 59kΩ.
Decreased resistor values are necessary to maintain
noise immunity on the FBB pin, resulting in increased
quiescent current. Table 3 summarizes the resistor val-
ues for various output voltages.
1
VOUT · (VIN(MAX) - VOUT
)
IRMS(MAX)
=
·
L · FS · VIN(MAX)
2 · 3
Dissipation due to the RMS current in the ceramic output
capacitor ESR is typically minimal, resulting in less than
a few degrees rise in hot-spot temperature.
Inductor Selection
V
V
3.3V
0.6V
⎛
⎝
⎞
⎛
⎝
⎞
⎠
R2 =
OUT -1 · R3 =
- 1 · 59kΩ = 267kΩ
⎠
The step-down converter uses peak current mode con-
trol with slope compensation to maintain stability for
duty cycles greater than 50%. The output inductor value
must be selected so the inductor current down slope
meets the internal slope compensation requirements.
The internal slope compensation for the AAT2552 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.
REF
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)
VOUT (V)
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
124
137
187
267
75
113
150
187
221
261
301
332
442
464
523
715
1000
0.75 ⋅ VO 0.75 ⋅ 1.8V
= 0.45
A
µsec
m =
=
L
3.0µH
0.75 ⋅ VO
0.75
⋅
VO
A
µsec
A
L =
=
≈
1.67
⋅ VO
m
0.45A
µsec
For most designs, the step-down converter operates with
inductor values from 1μH to 4.7μH. Table 6 displays induc-
tor values for the AAT2552 for various output voltages.
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
Table 3: Adjustable Resistor Values For
Step-Down Converter.
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Adjustable Output Voltage for the LDO
Printed Circuit Board
Layout Considerations
The output voltage for the LDO can be programmed by
an external resistor divider network.
For the best results, it is recommended to physically
place the battery pack as close as possible to the
AAT2552 BAT pin. To minimize voltage drops on the PCB,
keep the high current carrying traces adequately wide.
Refer to the AAT2552 evaluation board for a good layout
example (see Figures 6 and 7). The following guidelines
should be used to help ensure a proper layout.
As shown below, the selection of R4 and R5 is a straight-
forward matter. R5 is chosen by considering the tradeoff
between the feedback network bias current and resistor
value. Higher resistor values allow stray capacitance to
become a larger factor in circuit performance whereas
lower resistor values increase bias current and decrease
efficiency. To select appropriate resistor values, first
choose R5 such that the feedback network bias current
is reasonable. Then, according to the desired VOUT, calcu-
late R4 according to the equation below. An example
calculation follows.
1. The input capacitors (C1, C6) should connect as
closely as possible to ADP, INA, and INB. It is pos-
sible to use two input capacitors for INA and INB.
2. C4 and L1 should be connected as closely as possi-
ble. 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.
⎛ VOUT
⎝ VREF
⎞
R4 =
- 1 · R5
⎠
3. The feedback pin 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 regulation. Feedback resistors
should be placed as closely as possible to the FBB
pin to minimize the length of the high impedance
feedback trace. If possible, they should also be
placed away from the LX (switching node) and induc-
tor to improve noise immunity.
4. The resistance of the trace from PGND should be
kept to a minimum. This will help to minimize any
error in DC regulation due to differences in the
potential of the internal signal ground and the power
ground.
An R5 value of 59kΩ is chosen, resulting in a small feed-
back network bias current of 1.24V/59kΩ ≈ 21μA. The
desired output voltage is 1.8V. From this information, R4
is calculated from the equation below. The result is R4 =
26.64kΩ. Since 26.64kΩ is not a standard 1%-value,
26.7kΩ is selected. From this example calculation, for
VOUT = 1.8V, use R5 = 59kΩ and R4 = 26.7kΩ. Example
output voltages and corresponding resistor values are
provided in Table 4.
R4 Standard 1% Values
VOUT (V)
(R5 = 59kΩ)
R4 (kΩ)
5. A high density, small footprint layout can be achieved
using an inexpensive, miniature, non-shielded, high
DCR inductor.
3.3
2.8
2.5
2.0
1.8
1.5
97.6
75.0
60.4
36.5
26.7
12.4
Table 4: Adjustable Resistor Values for the LDO.
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2552.2008.02.1.2
23
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
JP1
EN_BAT
2
1
3 2 1
Power Selection
JP2
BAT
ADP
D1
RED
LED
C6
10μF
(at bottom layer)
C1
10μF
1
2
R6
EN_LDO
U1
JP3
1.5K
Sync/Mode
15
16
1
10
11
7
ADP
INA
1
2
STAT
INB
ENA
ENB
EN_BAT
MODE
6
5
EN_BUCK
VoB
L1
14
2
12
4
BAT
LX
C4
100pF
(Optional)
ISET
FBB
VoA
C2
10μF
R2
3
9
8
AGND
PGND
OUTA
FBA
R1
8.06K
13
R4
C3
4.7μF
R3
59k
C5
4.7μF
R5
59k
VOUTB (V) R2 (Ω)
L1
VOUTA (V)
R4 (Ω)
0.6
13
R2 short, R3 open
1.24
1.5
1.8
2.0
2.5
2.8
3.0
R4 short, R5 open
12.4K
9.2K
59K
1.5μH (CDRH2D09/HP; DCR 88mΩ; 730mA @ 20°C)
2.2μH (CDRH2D09/HP; DCR 115mΩ; 600mA @ 20°C)
3.0μH (CDRH2D09/HP; DCR 150mΩ; 470mA @ 20°C)
3.9μH (CDRH2D09/HP; DCR 180mΩ; 450mA @ 20°C)
4.7μH (CDRH2D09/HP; DCR 230mΩ; 410mA @ 20°C)
5.6μH (CDRH2D09/HP; DCR 260mΩ; 370mA @ 20°C)
1.2
1.8
2.5
3.0
3.3
26.7K
36.5K
118K
187K
237K
267K
60.4K
75.0K
97.6K
Figure 5: AAT2552 Evaluation Board Schematic.
Figure 6: AAT2552 Evaluation Board
Top Side Layout.
Figure 7: AAT2552 Evaluation Board
Bottom Side Layout.
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24
2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Component
Part Number
Description
Manufacturer
U1
C1, C2
C3, C5
C6
C4
L1
R6
R1
AAT2552IRN
ECJ-1VB0J106M
GRM188R60J475KE19
GRM319R61A106KE19
GRM1886R1H101JZ01J
CDRH2D09
Total Power Solution for Portable Applications
CER 10ꢀF 6.3V X5R 0603
CER 4.7ꢀF 6.3V X5R 0603
CER 10ꢀF 10V X5R 1206
CER 100pF 50V 5% R2H 0603
Shielded SMD, 3x3x1mm
1.5KΩ, 5%, 1/4W 0603
8.06KΩ, 1%, 1/4W 0603
118KΩ, 1%, 1/4W 0603
59KΩ, 1%, 1/4W 0603
AnalogicTech
Panansonic
Murata
Murata
Murata
Sumida
Vishay
Vishay
Vishay
Vishay
Chip Resistor
Chip Resistor
Chip Resistor
Chip Resistor
R2
R3, R5
R4
JP1, JP2, JP3, JP4
D1
Chip Resistor
PRPN401PAEN
CMD15-21SRC/TR8
60.4KΩ, 1%, 1/4W 0603
Conn. Header, 2mm zip
Red LED 1206
Vishay
Sullins Electronics
Chicago Miniature Lamp
Table 5: AAT2552 Evaluation Board Component Listing.
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2552.2008.02.1.2
25
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Step-Down Converter Design Example (to be updated)
Specifications
VO = 1.8V @ 250mA, Pulsed Load ΔILOAD = 200mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS
= 1.5MHz
TAMB = 85°C
1.8V Output Inductor
µsec
A
µsec
A
(use 3.0μH; see Table 3)
L1 = 1.67
⋅ VO2 = 1.67
⋅ 1.8V = 3µH
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
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
w w w . a n a l o g i c t e c h . c o m
26
2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
AAT2552 Losses
IO2 · (RDSON(H) · VO + RDSON(L) · [VIN -VO])
PTOTAL
=
VIN
+ (tsw · FS · IO + IQ) · VIN
0.22 · (0.59Ω · 1.8V + 0.42Ω · [4.2V - 1.8V])
4.2V
=
+ (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
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2552.2008.02.1.2
27
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Output Voltage
VOUTB (V)
R3 = 59kΩ
R3 (kΩ)
R3 = 221kΩ
R1 (kΩ)
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
R2 short, R3 open
R2 short, R3 open
1.5
1.5
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
4.9
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
237
75
113
150
187
221
261
301
332
442
464
523
715
887
1000
3.3
267
5.6
Table 6: Step-Down Converter Component Values.
Inductance
Max DC
Current (mA)
DCR
(mΩ)
Size (mm)
LxWxH
Manufacturer
Part Number
(μH)
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
NR3010T2R2M
NR3010T3R3M
NR3010T4R7M
MIPWT3226D-1R5
MIPWT3226D-2R2
MIPWT3226D-3R0
MIPWT3226D-4R2
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
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Shielded
Chip shielded
Chip shielded
Chip shielded
Chip shielded
98
123
170
80
95
140
190
90
100
120
140
FDK
FDK
FDK
Table 7: Suggested Inductors and Suppliers.
1. For reduced quiescent current, R3 = 221kΩ.
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28
2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Manufacturer
Part Number
Value (μF)
Voltage Rating
Temp. Co.
Case Size
Murata
Murata
Murata
Murata
Murata
Murata
GRM21BR61A106KE19
GRM188R60J475KE19
GRM188R61A225KE34
GRM188R60J225KE19
GRM188R61A105KA61
GRM185R60J105KE26
10
10
6.3
10
6.3
10
X5R
X5R
X5R
X5R
X5R
X5R
0805
0603
0603
0603
0603
0603
4.7
2.2
2.2
1.0
1.0
6.3
Table 8: Surface Mount Capacitors.
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2552.2008.02.1.2
29
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN34-16
UVXYY
AAT2552IRN-CAE-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/about/quality.aspx.
Legend
Voltage
Code
Adjustable
(0.6)
0.9
Adjustable
(1.2)
A
B
E
1.5
1.8
1.9
2.5
2.6
2.7
2.8
2.85
2.9
3.0
3.3
4.2
G
I
Y
N
O
P
Q
R
S
T
W
C
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
w w w . a n a l o g i c t e c h . c o m
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2552.2008.02.1.2
PRODUCT DATASHEET
AAT2552178
SystemPowerTM
Total Power Solution for Portable Applications
Package Information1
TDFN34-16
3.000 0.050
1.600 0.050
Detail "A"
Index Area
0.350 0.100
Top View
Bottom View
C0.3
(4x)
Pin 1 Indicator
(optional)
0.050 0.050
0.229 0.051
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.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© 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. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control 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 registered trademarks or trademarks of their respective holders.
w w w . a n a l o g i c t e c h . c o m
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31
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