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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems General Description
The AAT2557 is a fully integrated 500mA battery charger 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 linear regulator, making it ideal for applications operating with single-cell lithium-ion/polymer batteries. The battery charger is a complete constant current/constant voltage linear charger. It offers an integrated pass device, reverse blocking protection, high accuracy current and voltage regulation, charge status, and charge termination. The charging current is programmable via external resistor from 15mA to 500mA. In addition to these standard features, the device offers over-voltage, current limit, and thermal protection. The linear regulator is designed for fast transient response and good power supply ripple rejection. Capable of up to 300mA load current, it includes short-circuit protection and thermal shutdown. The AAT2557 is available in a Pb-free, thermallyenhanced TSOPJW-14 package and is rated over the -40C to +85C temperature range.
Features
*
SystemPowerTM
*
* * *
Battery Charger: -- Input Voltage Range: 4V to 6.5V -- Programmable Charging Current up to 500mA -- Highly Integrated Battery Charger * Charging Device * Reverse Blocking Diode Linear Regulator: -- 300mA Output Current -- Low Dropout: 400mV at 300mA -- Fast Line and Load Transient Response -- High Accuracy: 1.5% -- 70A Quiescent Current Short-Circuit, Over-Temperature, and Current Limit Protection TSOPJW-14 Package -40C to +85C Temperature Range
Applications
* * * * * * Bluetooth(R) Headsets Cellular and DECT Phones Handheld Instruments MP3 and Portable Music Players PDAs and Handheld Computers Portable Media Players
Typical Application
Adapter/USB Input
ADP STAT INLDO C INLDO
Charger Enable LDO Enable
VOUTLDO
EN_BAT
System
AAT2557
ENLDO OUTLDO C OUTLDO BYP C BYP GND ISET BAT
BATT+
C BAT
BATTRSET Battery Pack
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Pin Descriptions
Pin #
1
Symbol
ENLDO
Function
Enable pin for the linear regulator. When connected to logic low, the regulator is disabled and consumes less than 1A of current. When connected to logic high, it resumes normal operation. Ground. Low noise bypass pin. Connect a 10nF capacitor between this pin and ground to improve AC ripple rejection and reduce noise. Enable pin for the battery charger. When connected to logic low, the battery charger is disabled and consumes less than 1A of current. When connected to logic high, the charger resumes normal operation. Charge current set point. Connect a resistor from this pin to ground. Refer to typical characteristics curves for resistor selection. Battery charging and sensing. Input for USB/adapter charger. Charge status input. Open drain status output. Linear regulator output. Connect a 2.2F capacitor from this pin to ground. Linear regulator input voltage. Connect a 1F or greater capacitor from this pin to ground.
2, 8, 12, 13, 14 3 4
GND BYP EN_BAT
5 6 7 9 10 11
ISET BAT ADP STAT OUTLDO INLDO
Pin Configuration
TSOPJW-14 (Top View)
ENLDO GND BYP EN_BAT ISET BAT ADP
1 2 3 4 5 6 7
14 13 12 11 10 9 8
GND GND GND INLDO OUTLDO STAT GND
2
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Absolute Maximum Ratings1
Symbol
VINLDO VADP VEN VX VBYP TJ TLEAD
Description
Input Voltage to GND Adapter Voltage to GND ENLDO, EN_BAT Voltage to GND BAT, ISET, STAT Voltage to GND BYP Voltage to GND Operating Junction Temperature Range Maximum Soldering Temperature (at leads, 10 sec)
Value
6.0 -0.3 to 7.5 -0.3 to 6.0 -0.3 to VADP + 0.3 -0.3 to VINLDO + 0.3 -40 to 150 300
Units
V V V V V C C
Thermal Information
Symbol
PD JA
Description
Maximum Power Dissipation Thermal Resistance2
Value
625 160
Units
mW 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. 2557.2007.06.1.0
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Electrical Characteristics1
VINLDO = VOUT(NOM) + 1V for VOUT options greater than 1.5V. IOUT = 1mA, COUT = 2.2F, CIN = 1F, CBYP = 10nF, TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol Description Conditions
IOUTLDO = 1mA TA = 25C to 300mA TA = -40C to +85C
Min
-1.5 -2.5 VOUT + VDO2
Typ
Max
1.5 2.5 5.5
Units
Linear Regulator VOUT VIN VDO VOUT/ VOUT*VIN VOUT(Line) VOUT(Load) IOUT ISC IQ ISHDN PSRR Output Voltage Tolerance Input Voltage Dropout Voltage3 Line Regulation Dynamic Line Regulation IOUTLDO = 300mA VINLDO = VOUTLDO + 1 to 5.0V % V mV %/V mV mV mA mA A A dB
400 0.09 2.5 60 300 600 70 65 45 43 145 12 50 22 15
600
TSD THYS eN TC TEN_DLY VEN(L) VEN(H) IEN
IOUTLDO = 300mA, VINLDO = VOUTLDO + 1 to VOUTLDO + 2, TR/TF = 2s Dynamic Load Regulation IOUTLDO = 1mA to 300mA, TR <5s Output Current VOUTLDO > 1.2V Short-Circuit Current VOUTLDO < 0.4V Quiescent Current VINLDO = 5V; VENLDO = VIN Shutdown Current VINLDO = 5V; VENLDO = 0V 1kHz Power Supply Rejection IOUTLDO =10mA 10kHz Ratio 1MHz Over-Temperature Shutdown Threshold Over-Temperature Shutdown Hysteresis Output Noise Output Voltage Temperature Coefficient Enable Time Delay BYP Open Enable Threshold Low Enable Threshold High Enable Input Current VENLDO = 5.5V
125 1.0
C C VRMS ppm/C s V V A
0.6 1.5 1.0
1. The AAT2557 is guaranteed to meet performance specifications over the -40C to +85C 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.
4
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Electrical Characteristics1
VADP = 5V; TA = -40C to +85C, unless otherwise noted. Typical values are TA = 25C. Symbol Description Conditions Min Typ Max Units
Battery Charger Operation VADP Adapter Voltage Range Under-Voltage Lockout (UVLO) VUVLO UVLO Hysteresis IOP Operating Current ISHUTDOWN Shutdown Current ILEAKAGE Reverse Leakage Current from BAT Pin Voltage Regulation VBAT_EOC End of Charge Accuracy VCH/VCH Output Charge Voltage Tolerance VMIN Preconditioning Voltage Threshold VRCH Battery Recharge Voltage Threshold Current Regulation ICH Charge Current Programmable Range ICH/ICH Charge Current Regulation Tolerance VSET ISET Pin Voltage KI_A Current Set Factor: ICH/ISET Charging Devices RDS(ON) Charging Transistor On Resistance Logic Control/Protection VEN(H) Enable Threshold High VEN(L) Enable Threshold Low VSTAT Output Low Voltage ISTAT STAT Pin Current Sink Capability VOVP Over-Voltage Protection Threshold ITK/ICHG Pre-Charge Current ITERM/ICHG Charge Termination Threshold Current
Rising Edge Charge Current = 200mA VBAT = 4.25V, EN_BAT = GND VBAT = 4V, ADP Pin Open
4.0 3 150 0.5 0.3 0.4 4.158 2.85 4.20 0.5 3.0 -0.1
6.5 4 1 1 2 4.242 3.15
V V mV mA A A V % V V mA % V
Measured from VBAT_EOC 15
500 10 2 800
VADP = 5.5V 1.6 STAT Pin Sinks 4mA
0.9
1.1
V V V mA V % %
0.4 0.4 8 4.4 10 10
ICH = 100mA
1. The AAT2557 is guaranteed to meet performance specifications over the -40C to +85C operating temperature range and is assured by design, characterization, and correlation with statistical process controls. 2557.2007.06.1.0
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Typical Characteristics - Battery Charger
Constant Charging Current vs. Set Resistor Values
1000
600 500
Charging Current vs. Battery Voltage
(VADP = 5V) RSET = 3.24k
ICH (mA)
ICH (mA)
100
400 300 200 100
RSET = 5.36k RSET = 8.06k RSET = 16.2k RSET = 31.6k
10
1
0
1
10
100
1000
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
RSET (k)
VBAT (V)
End of Charge Battery Voltage vs. Supply Voltage
4.206
End of Charge Voltage Regulation vs. Temperature
(RSET = 8.06k)
4.23
4.204
RSET = 8.06k
VBAT_EOC (V)
6.5
4.22 4.21 4.20 4.19 4.18
VBAT_EOC (V)
4.202 4.200 4.198 4.196 4.194
RSET = 31.6k
4.5
4.75
5
5.25
5.5
5.75
6
6.25
4.17
-50
-25
0
25
50
75
100
VADP (V)
Temperature (C)
Constant Charging Current vs. Supply Voltage
(RSET = 8.06k)
220 210
Constant Charging Current vs. Temperature
(RSET = 8.06k)
210 208
ICH (mA)
200 190 180 170
ICH (mA)
6.5
VBAT = 3.3V VBAT = 4V
205 203 200 198 195 193 190
VBAT = 3.6V
4
4.25
4.5
4.75
5
5.25
5.5
5.75
6
6.25
-50
-25
0
25
50
75
100
VADP (V)
Temperature (C)
6
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Typical Characteristics - Battery Charger
Operating Current vs. Temperature
(RSET = 8.06k)
550 3.03 500 3.02
Preconditioning Threshold Voltage vs. Temperature
(RSET = 8.06k)
VMIN (V)
IOP (A)
450 400 350 300 -50
3.01 3 2.99 2.98 2.97 -50
-25
0
25
50
75
100
-25
0
25
50
75
100
Temperature (C)
Temperature (C)
Preconditioning Charge Current vs. Temperature
(RSET = 8.06k)
60 50
Preconditioning Charge Current vs. Supply Voltage
RSET = 3.24k
20.8 20.6
ITRICKLE (mA)
ITRICKLE (mA)
20.4 20.2 20.0 19.8 19.6 19.4 19.2 -50 -25 0 25 50 75 100
40 30 20 10 0 4 4.2
RSET = 5.36k RSET = 8.06k RSET = 16.2k
4.4 4.6 4.8 5
RSET = 31.6k
5.2 5.4 5.6 5.8 6 6.2 6.4
Temperature (C)
VADP (V)
Recharging Threshold Voltage vs. Temperature
(RSET = 8.06k)
800 700 600
Sleep Mode Current vs. Supply Voltage
(RSET = 8.06k)
4.18 4.16
85C
ISLEEP (nA)
4.14
VRCH (V)
4.12 4.10 4.08 4.06 4.04 4.02 -50 -25 0 25 50 75 100
500 400 300 200 100 0 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5
25C
-40C
Temperature (C)
VADP (V)
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Typical Characteristics - Battery Charger
VEN(H) vs. Supply Voltage
(RSET = 8.06k)
1.2 1.1 1.1 1
VEN(L) vs. Supply Voltage
(RSET = 8.06k)
-40C
-40C
VEN(L) (V)
VEN(H) (V)
1 0.9 0.8 0.7 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5
0.9 0.8 0.7 0.6 4 4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5
25C
85C
25C
85C
VADP (V)
VADP (V)
8
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Typical Characteristics - LDO Regulator
Dropout Voltage vs. Temperature
540
3.2
Dropout Characteristics
Dropout Voltage (mV)
480 420 360 300 240 180 120 60 0
IL = 300mA
3.0
IOUT = 0mA
Output Voltage (V)
2.8 2.6 2.4 2.2 2.0 2.7
IL = 150mA
IL = 100mA
IOUT = 300mA IOUT = 150mA IOUT = 10mA
2.8
IL = 50mA
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120
IOUT = 100mA IOUT = 50mA
2.9
3.0
3.1
3.2
3.3
Temperature (C)
Input Voltage (V)
Dropout Voltage vs. Output Current
500
90 80 70 60 50 40 30 20 10
Ground Current vs. Input Voltage
Dropout Voltage (mV)
400 350 300 250 200 150 100 50 0 0 50 100 150 200 250 300
Ground Current (A)
450
85C 25C -40C
IOUT=300mA IOUT=0mA IOUT=150mA IOUT=50mA
IOUT=10mA
0 2 2.5 3 3.5 4 4.5 5
Output Current (mA)
Input Voltage (V)
Quiescent Current vs. Temperature
100
Output Voltage vs. Temperature
1.203 1.202
Quiescent Current (A)
90
Output Voltage (V)
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100 110 120
80 70 60 50 40 30 20 10 0
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
Temperature (C)
Temperature (C)
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
Typical Characteristics - LDO Regulator
LDO Initial Power-Up Response Time
6
LDO Turn-On Time from Enable
(VIN Present)
4
Output Voltage (bottom) (V)
Output Voltage (bottom) (V)
Enable Voltage (top) (V)
Input Voltage (top) (V)
5 4 3 2 1 0 3 2 1 0
3 2 1 0 4 3 2 1 0
Time (50s/div)
Time (5s/div)
Turn-Off Response Time
(IOUT = 100mA)
6
Line Transient Response
Output Voltage (bottom) (V)
Output Voltage (bottom) (V)
Enable Voltage (top) (V)
Input Voltage (top) (V)
5 0 3 2 1 0
5 4
VIN
3.00
VOUT
2.99 2.98
Time (5s/div)
Time (100s/div)
Load Transient Response
2.90
Load Transient Response 300mA
(VOUT = 2.8V)
Output Current (bottom) (mA)
Output Current (bottom) (mA)
3.0
(VOUT = 2.8V) VOUT
Output Voltage (top) (V)
Output Voltage (top) (V)
2.85 2.80 2.75
2.9 2.8 2.7
VOUT
400 300 200
100 0
IOUT Time (100s/div)
IOUT
100 0
Time (10s/div)
10
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Typical Characteristics - LDO Regulator
VEN(L) and VEN(H) vs. VIN
Enable Threshold Voltage (V)
1.250 1.225 1.200 1.175 1.150 1.125 1.100 1.075 1.050 2.5 3.0 3.5 4.0 4.5 5.0 5.5
VEN(H)
VEN(L)
Input Voltage (V)
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Functional Block Diagram
Reverse Blocking
ADP
-
BAT
+
STAT
OverTemperature Protection
UVLO
INLDO
Err. Amp.
OverCurrent Protection
OUTLDO ENLDO GND
Functional Description
The AAT2557 is a high performance power management IC comprised of a lithium-ion/polymer battery charger and a linear regulator. The linear regulator is designed for high-speed turn-on, fast transient response, good power supply ripple rejection, and low noise.
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 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 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.
12
+
ISET
Constant Current
Charge Control
VREF
EN_BAT
BYP
VREF
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
Linear Regulator
The advanced circuit design of the linear regulator has been specifically optimized for very fast startup. This proprietary CMOS LDO has also been tailored for superior transient response characteristics. These traits are particularly important for applications that require fast power supply timing. The high-speed turn-on capability is enabled through implementation of a fast-start control circuit 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 lowcost, low-ESR ceramic capacitors; however, the design will allow for operation over a wide range of capacitor types. The regulator comes with complete short-circuit and thermal protection. The combination of these two internal protection circuits gives a comprehensive safety system to guard against extreme adverse operating conditions. The regulator features an enable/disable function. This pin (ENLDO) is active high and is compatible with CMOS logic. To assure the LDO regulator will switch on, the ENLDO 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 ENLDO pin falls below 0.6V. If the enable function is not needed in a specific application, it may be tied to INLDO to keep the LDO regulator in a continuously on state.
Protection Circuitry
Over-Voltage Protection A battery charger over-voltage protection event is defined as a condition where the voltage on the BAT pin exceeds the over-voltage protection threshold (VOVP) (4.4V). 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. Over-Temperature Protection 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 (145C). Once the internal die temperature falls below the thermal limit, normal charging operation will resume. Short-Circuit Protection The AAT2557's LDO contains an internal short-circuit protection circuit that will trigger when the output load current exceeds the internal threshold limit. Under short-circuit conditions, the output of the LDO regulator will be current limited until the short-circuit condition is removed from the output or until the package power dissipation exceeds the device thermal limit. Thermal Protection The AAT2557's LDO has an internal thermal protection circuit which will turn on when the device die temperature exceeds 145C. The internal thermal protection circuit will actively turn off the LDO regulator output pass device to prevent the possibility of overtemperature damage. The LDO regulator output will remain in a shutdown state until the internal die temperature falls back below the 145C trip point. The combination and interaction between the shortcircuit and thermal protection systems allow the LDO regulator to withstand indefinite short-circuit conditions without sustaining permanent damage.
Under-Voltage Lockout
The AAT2557 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 appropriate mode for the condition of the battery.
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
Battery Charging Operation
Battery charging commences only after checking several conditions in order to maintain a safe charging 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 battery voltage is below VMIN, the charger begins battery pre-conditioning by charging at 10% of the programmed 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. 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 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-saving sleep mode. During this time, the series pass device will block current in both directions, 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 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.
Preconditioning Trickle Charge Phase Charge Complete Voltage Regulated Current
Constant Current Charge Phase I = Max CC
Constant Voltage Charge Phase
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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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
Battery Charging System Operation Flow Chart
Enable
Power On Reset
No
Yes
Power Input Voltage VADP > VUVLO
Yes
Shut Down
Yes
Fault Conditions Monitoring OV, OT
Charge Control
No
Preconditioning Test V MIN > VBAT
Yes
Preconditioning (Trickle Charge)
No No Recharge Test V RCH > VBAT Yes Current Phase Test V BAT_EOC > VBAT Yes Constant Current Charge Mode
No
Voltage Phase Test IBAT > ITERM
Yes
Constant Voltage Charge Mode
No
Charge Completed
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems 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 appropriate charging mode based on the battery charge state and measured cell voltage from the BAT pin. The LDO is enabled when the ENLDO pin is pulled high. The control and feedback circuits have been optimized for high-speed, monotonic turn-on characteristics.
1000
Normal ICHARGE (mA)
500 400 300 250 200 150 100 50 40 30 20 15
Set Resistor Value R1 (k)
3.24 4.12 5.36 6.49 8.06 10.7 16.2 31.6 38.3 53.6 78.7 105
Table 1: RSET 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 6.5V 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 values for a desired constant current charge level.
ICH (mA)
100
10
1 1 10 100 1000
RSET (k)
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 trickle charge current, is dominated by the tolerance of the set resistor used. For this reason, a 1% tolerance metal film resistor is recommended for the set resistor function. Fast charge constant current levels from 15mA to 500mA may be set by selecting the appropriate resistor value from Table 1.
Figure 2: Constant Charging Current vs. Set Resistor Values.
Charge Status Output
The AAT2557 provides battery charge status via a status pin. This pin is internally connected to an Nchannel open drain MOSFET, which can be used to drive an external LED. The status pin can indicate several conditions, as shown in Table 2.
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
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. First, the maximum power dissipation for a given situation should be calculated:
Event Description
No battery charging activity Battery charging via adapter or USB port Charging completed
Status
OFF ON OFF
Table 2: LED Status Indicator. The LED should be biased with as little current as necessary to create reasonable illumination; therefore, 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. The required ballast resistor values can be estimated using the following formulas:
PD(MAX) =
Where:
(TJ(MAX) - TA) JA
PD(MAX) = Maximum Power Dissipation (W) JA = Package Thermal Resistance (C/W) TJ(MAX) = Maximum Device Junction Temperature (C) [135C] TA = Ambient Temperature (C)
R 1=
Example:
(VADP - VF(LED)) ILED
PD = [(VADP - VBAT) * ICH + (VADP * IOP)] + (VINLDO - VOUTLDO) ILDOLOAD + VINLDO * IQLDO
Where: PD = Total Power Dissipation by the Device = ADP/USB Voltage = Battery Voltage as Seen at the BAT Pin = Constant Charge Current Programmed for the Application = Quiescent Current Consumed by the Charger IC for Normal Operation [0.5mA] = Input Voltage as Seen at the INLDO Pin
R1 =
(5.5V - 2.0V) = 1.75k 2mA
VADP VBAT ICH IOP
Note: Red LED forward voltage (VF) is typically 2.0V @ 2mA.
Thermal Considerations
The AAT2557 is offered in a TSOPJW-14 package which can provide up to 625mW of power dissipation when it is properly bonded to a printed circuit board and has a maximum thermal resistance of 160C/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 VINLDO
VOUTLDO = Output Voltage as Seen at the OUTLDO Pin ILDOLOAD = LDO Load Current IQLDO = LDO Quiescent Current
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
By substitution, we can derive the maximum charge current before reaching the thermal limit condition (thermal cycling). The maximum charge current is the key factor when designing battery charger applications. Linear Regulator Output Capacitor For proper load voltage regulation and operational stability, 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 1.0F to 10F range are recommended for best performance. Applications utilizing the exceptionally low output noise and optimum power supply ripple rejection should use 2.2F 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 0.47F. Battery Charger Output Capacitor The AAT2557 only requires a 1F ceramic capacitor on the BAT pin to maintain circuit stability. This value should be increased to 10F or more if the battery connection is made any distance from the charger output. If the AAT2557 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 10F may be required to prevent the device from cycling on and off when no battery is present. Bypass Capacitor and Low Noise Applications A bypass capacitor pin is provided to enhance the low noise characteristics of the AAT2557 LDO regulator. The bypass capacitor is not necessary for operation of the AAT2557. However, for best device performance, a small ceramic capacitor should be placed between the bypass pin (BYP) and the device ground pin (GND). The value of CBYP may range from 470pF to 10nF. For lowest noise and best possible power supply ripple rejection performance, a 10nF capacitor should be used. To practically realize the highest power supply ripple rejection and lowest output noise performance, it is critical that the capacitor connection between the BYP pin and GND pin be direct and PCB traces should be as short as possible. Refer to the PCB Layout Recommendations section of this document for examples. There is a relationship between the bypass capacitor value and the LDO regulator turn-on and turnoff time. In applications where fast device turn-on and
ICH(MAX) =
(PD(MAX) - VIN * IOP) VIN - VBAT
(TJ(MAX) - TA) - V * I IN OP JA ICH(MAX) = VIN - VBAT
In general, the worst condition is the greatest voltage drop across the IC, when battery voltage is charged up to the preconditioning voltage threshold.
Capacitor Selection
Linear Regulator Input Capacitor An input capacitor greater than 1F will offer superior input line transient response and maximize power supply 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 inherent capability over tantalum capacitors to withstand input current surges from low impedance sources such as batteries in portable devices. Battery Charger Input Capacitor 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 1F to 22F 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 10F 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.
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2557.2007.06.1.0
AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
turn-off time are desired, the value of CBYP should be reduced. In applications where low noise performance and/or ripple rejection are less of a concern, the bypass capacitor may be omitted. The fastest device turn-on time will be realized when no bypass capacitor is used.
Printed Circuit Board Layout Considerations
For the best results, it is recommended to physically place the battery pack as close as possible to the AAT2557 BAT pin. To minimize voltage drops on the PCB, keep the high current carrying traces adequately wide. The input capacitors should connect as closely as possible to ADP and INLDO.
2557.2007.06.1.0
19
AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems
Manufacturer
Murata Murata Murata Murata Murata Murata Murata Murata
Part Number
GRM21BR61A106KE19 GRM188R60J475KE19 GRM188R61A225KE34 GRM188R60J225KE19 GRM188R61A105KA61 GRM185R60J105KE26 GRM188F51H103ZA01 GRM155F51H103ZA01
Value (F)
10 4.7 2.2 2.2 1.0 1.0 0.01 0.01
Voltage Rating
10 6.3 10 6.3 10 6.3 50 50
Temp. Co.
X5R X5R X5R X5R X5R X5R Y5V Y5V
Case Size
0805 0603 0603 0603 0603 0603 0603 0402
Table 3: Surface Mount Capacitors.
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2557.2007.06.1.0
AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Ordering Information
Package
TSOPJW-14
Marking1
VKXYY
Part Number (Tape and Reel)2
AAT2557ITO-CT-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 1.2 1.5 1.8 1.9 2.5 2.6 2.7 2.8 2.85 2.9 3.0 3.3 4.2 Code E 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. 2557.2007.06.1.0
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AAT2557
500mA Battery Charger and 300mA LDO Regulator for Portable Systems Package Information
TSOPJW-14
0.20 BSC
2.40 0.10
0.40 BSC
Top View
2.85 0.20
7 NOM + 0.05 3.05 - 0.10
+ 0.000 1.00 - 0.075
0.04 REF
+ 0.05 1.05 - 0.00
+ 0.05 0.05 - 0.04
4 4 2.75 0.25
0.15 0.05
0.45 0.15
All dimensions in millimeters.
(c) 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085 Phone (408) 737-4600 Fax (408) 737-4611 22
2557.2007.06.1.0

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