AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
1
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
General Description
The AAT3681A BatteryManager is an integrated single cell
lithium-ion/polymer battery charger IC, designed to oper-
ate from a DC power source or USB port up to an input
voltage of 7.5V. It requires just one external component.
The AAT3681A precisely regulates battery charge volt-
age and current for 4.2V (4.375V option) lithium-ion/
polymer battery cells. When charged from an AC adapt-
er or USB port, the battery charging current can be set
by an external resistor up to 500mA.
Battery charge state is continuously monitored for fault
conditions. In the event of an over-voltage, short-circuit,
or over-temperature failure, the device will automati-
cally shut down, thus protecting the charging device,
control system, and the battery under charge. A status
monitor output pin is provided to indicate the battery
charge status by directly driving an external LED.
The AAT3681A is available in a Pb-free, thermally
enhanced, space-saving 8-pin 2.0 × 2.0mm SC70JW
package and is specified for operation over the -40°C to
+85°C temperature range.
Features
• USBorACAdapterSystemPowerCharger
▪ Programmable from 15mA to 500mA
• 4.0V~7.5VInputVoltageRange
• HighLevelofIntegrationwithInternal:
▪ Charging Device
▪ ReverseBlockingDiode
ConstantRegulatedOutputVoltage:
▪ 4.1 in AAT3681A-5
▪ 4.2 in AAT3681A-1/-2/-4
• AutomaticCurrentSensing
• AutomaticRechargeSequencing
• FullBatteryChargeAutoTurnOff/SleepMode/Charge
Termination
• ShutdownCurrent<1µA
• AutomaticTrickleChargeforBatteryPre-Conditioning
(AAT3681A-1/AAT3681A-4 is No Trickle Charge
Option)
• Over-VoltageandEmergencyThermalProtection
• PowerOnResetandSoftStart
• LEDStatusPin
• 8-Pin2.0×2.0mmSC70JWPackage
Applications
• Bluetooth®Headsets
• DECTHeadsets
• DigitalStillCameras
• MP3,PortableMusic,andPortableMediaPlayers
• PersonalDataAssistants(PDAs)
• WristWatches
• OtherLithium-Ion/PolymerBattery-PoweredDevices
Typical Application
AAT3681A
C
BATT-
Battery
Pack
ADP
GND
BAT
BATT+
RSET
Adapter/USB Input
STAT
EN
ISET
Enable
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
2Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
Pin Description
Pin # Symbol Type Function
1 EN In
Enable pin.
AAT3681A, AAT3681A-1, AAT3681A-4, AAT3681A-5:LogichighenablestheIC
(internal pull down 6MΩresistor).
AAT3681A-2:LogiclowenablestheIC(internalpulldownresistor).
2 ISET In/Out Connect resistor here to set the charge current.
3 BAT In/Out Battery charging and sensing.
4 ADP Power In Input from USB/adapter charger.
5STAT Out Opendrainstatuspin.
6, 7, 8 GND Power Ground connection.
Pin Configuration
SC70JW-8
(Top View)
ISET
BAT
ADP
GND
GND
GND
STAT
EN 1
2
3
45
6
7
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
3
AAT3681A Feature Options
Product Trickle Charge Enable
Charge Termination
Threshold Current
Constant Regulated Output
Voltage VCO(REG)
AAT3681A Yes ActiveHigh 10% 4.2(Optional4.1V)
AAT3681A-1 No ActiveHigh 10% 4.2
AAT3681A-2 Yes Active Low 10% 4.2
AAT3681A-4 No ActiveHigh 10% 4.2
AAT3681A-5 Yes ActiveHigh 10% 4.1
Absolute Maximum Ratings1
Symbol Description Value Units
VPADP Continuous -0.3 to 8.0 V
VNBAT, STAT, ISET, EN -0.3 to VP + 0.3
TAOperatingTemperatureRange -40 to 85
°CTJJunctionTemperatureRange -40 to 150
TLEAD Maximum Soldering Temperature (at Leads) 300
Thermal Information2
Symbol Description Value Units
PDMaximum Power Dissipation 0.687 W
qJA MaximumThermalResistance 160 °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.
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
4Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
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
Operation
VADP AdapterVoltageRange 4.0 7.5 V
VUVLO
Under-VoltageLockout(UVLO) RisingEdge for AAT3681A/-1/-2 3.0 V
RisingEdgeforAAT3681A-4/-5 3.2
UVLOHysteresis 150 mV
IOP OperatingCurrent Charge Current = 200mA 0.5 1 mA
ISHUTDOWN Shutdown Current
VBAT = 4.25V, VEN = GND (AAT3681A, AAT3681A-1,
AAT3681A-4) 0.3 1 µA
VBAT = 4.25V, VEN = 5V (AAT3681A-2)
ILEAKAGE
ReverseLeakageCurrentfrom
BAT Pin VBAT=4V,ADPPinOpen 0.4 2 µA
Voltage Regulation
VCO(REG) ConstantOutputVoltageAccuracy ForAAT3681A/-1/-2/-4 4.158 4.20 4.242 V
AAT3681A-5Only 4.059 4.10 4.141
DVCH/VCH OutputChargeVoltageTolerance 0.5 %
VMIN Preconditioning Voltage Threshold AAT3681A,AAT3681A-2Only 2.85 3.0 3.15 V
VRCH
BatteryRechargeVoltage
Threshold
AAT3681A, AAT3681A-1, AAT3681A-2 and
AAT3681A-4 Only;MeasuredfromVCO(REG)
-0.1 V
Current Regulation
ICH
Charge Current Programmable
Range215 500 mA
DICH/ICH
ChargeCurrentRegulation
Tolerance 10 %
VSET ISET Pin Voltage 2 V
KI_A CurrentSetFactor:ICH/ISET 800
Charging Devices
RDS(ON) ChargingTransistorOnResistance VADP = 5.5V 0.6 1 W
Logic Control/Protection
VEN(H) InputHighThreshold 1.6 V
VEN(L) Input Low Threshold 0.4 V
VSTAT OutputLowVoltage STAT Pin Sinks 4mA 0.4 V
ISTAT STAT Pin Current Sink Capability 8 mA
VOVP Over-VoltageProtectionThreshold 4.4 V
ITK/ICH Pre-Charge Current ICH=100mA;AAT3681A,AAT3681A-2,
and AAT3681A-5Only 10 %
ITERM/ICH
Charge Termination Threshold
Current
AAT3681A, AAT3681A-1, AAT3681A-2,
AAT3681A-4, and AAT3681A-5Only 10 %
1. TheAAT3681A outputcharge voltageisspecified over the0° to70°C ambienttemperaturerange; operation overthe-40°C to+85°Ctemperaturerangeis guaranteedby
design.
2. Achievable charge current may be limited by power dissipation capability of the package under certain operating conditions. See “Thermal Considerations” section of this
datasheet.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
5
Typical Characteristics
RSET (kΩ)
ICH (mA)
1
10
100
1000
110 100 1000
Constant Charging Current
vs. Set Resistor Values
Operating Supply Current vs. RSET
(VIN = 5V)
RSET (kΩ)
ISUPPLY (µA)
1
10
100
1000
110 100
VBAT = 2.85V
VBAT = 3.6V
Constant Regulated Output Voltage
vs. Input Voltage
(AAT3681A, AAT3681A-1/-2/-4)
Input Voltage (V)
Battery Voltage (V)
4.180
4.185
4.190
4.195
4.200
4.205
4.210
4.215
4.220
4.55.0 5.56.0 6.57.0 7.5
Constant Regulated Output Voltage
vs. Temperature
(AAT3681A, AAT3681A-1/-2/-4; RSET = 8.06kΩ)
Temperature (°C)
V
CO(REG)
(V)
4.17
4.18
4.19
4.20
4.21
4.22
4.23
-50-25 0255075 100
Constant Regulated Output Voltage
vs. Input Voltage
(AAT3681A-4.1, AAT3681A-5 Only)
Input Voltage (V)
End Of Charge
Voltage Regulation (V)
5.05.5 6.06.5 7.
07
.5
4.05
4.07
4.09
4.11
4.13
4.15
Constant Regulated Output Voltage
vs. Temperature
(AAT3681A-4.1 and AAT3681A-5 Only)
Temperature (°C)
End Of Charge
Voltage Regulation (V)
-40-15 10 35 60 85
4.080
4.085
4.090
4.095
4.100
4.105
4.110
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
6Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
Typical Characteristics
Charging Current vs. Battery Voltage
(AAT3681A, AAT3681A-2, and AAT3681A-5 only)
VBAT (V)
I
CH
(mA)
0
100
200
300
400
500
600
2.72.9 3.13.3 3.53.7 3.94.1 4.3
RSET = 8.06kΩ
RSET = 5.36kΩ
RSET = 3.24kΩ
RSET = 16.2kΩ
RSET = 31.6kΩ
Charging Current vs. Battery Voltage
(AAT3681A-1 and AAT3681A-4 only)
VBAT (V)
I
CH
(mA)
0
100
200
300
400
500
600
2.72.9 3.13.3 3.53.7 3.94.1 4.3
RSET = 8.06kΩ
RSET = 5.36kΩ
RSET = 3.24kΩ
RSET = 16.2kΩ
RSET = 31.6kΩ
Battery Charging Current vs. Input Voltage
(AAT3681A-4.1 and AAT3681A-5 only; VCO(REG) = 4.1V)
Input Voltage (V)
Battery Charging Current (mA)
4.04.5 5.05.5 6.06.5 7.07.5
150
160
170
180
190
200
210
220
230
VBAT = 3.3V
VBAT = 3.6V
VBAT = 3.9V
VBAT = 4.0V
Charging Current vs. Battery Voltage
(AAT3681A-4.1 and AAT3681A-5 Only)
Battery Voltage (V)
Battery Charging Current (mA)
2.62.8 3.03.2 3.43.6 3.84.0 4.2
-100
0
100
200
300
400
500
600 RSET = 3.24KΩ
RSET = 5.36KΩ
RSET = 8.06KΩ
RSET = 16.2KΩ
RSET = 31.6KΩ
Battery Charging Current vs. Battery Voltage
(AAT3681A-4.1 and AAT3681A-5 Only)
Battery Voltage (V)
Battery Charging Current (mA)
2.62.8 3.02.22.4 3.23.4 3.63.8 4.04.2
0
40
80
120
160
200
240
VBAT = 5.0V
VBAT = 5.5V
VBAT = 6.0V
VBAT = 6.5V
VBAT = 7.0V
VBAT = 7.5V
Constant Charging Current vs. Temperature
(RSET = 8.06kΩ)
Temperature (°C)
ICH (mA)
190
193
195
198
200
203
205
208
210
-50 -25 0255075 100
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
7
Typical Characteristics
Constant Charging Current vs. Input Voltage
(RSET = 8.06kΩ)
Input Voltage (V)
Charging Current (mA)
120
140
160
180
200
220
240
260
280
4 4.5 5 5.5 6 6.5 7 7.5
VBAT = 3.3V
VBAT = 3.6V
VBAT = 4.0V
Operating Current vs. Temperature
(RSET = 8.06kΩ)
Temperature (°C)
IOP (µA)
300
350
400
450
500
550
-50 -25 0255075 100
Preconditioning Threshold Voltage vs. Temperature
(RSET = 8.06kΩ; AAT3681A, AAT3681A-2,
and AAT3681A-5 Only)
Temperature (°C)
VMIN (V)
2.97
2.98
2.99
3
3.01
3.02
3.03
-50-25 0255075 100
Preconditioning Voltage Threshold
vs. Input Voltage
(AAT3681A-4.1 and AAT3681A-5 Only)
Input Voltage (V)
Preconditioning
Threshold Voltage (V)
5.05.5 6.06.5 7.
07
.5
2.90
2.91
2.92
2.93
2.94
2.95
Preconditioning Threshold Voltage
vs. Temperature
(AAT3681AIJS-4.1-T1 Only)
Temperature (°C)
Preconditioning
Threshold Voltage (V)
-40-15 10 35 60 85
2.80
2.82
2.84
2.86
2.88
2.90
2.92
2.94
2.96
2.98
3.00
Preconditioning Charge Current vs. Temperature
(RSET = 8.06kΩ; AAT3681A, AAT3681A-2,and AAT3681A-5 Only)
Temperature (°C)
I
TRICKLE
(mA)
19.2
19.4
19.6
19.8
20.0
20.2
20.4
20.6
20.8
-50-25 0255075 100
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
8Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
Typical Characteristics
Preconditioning Charge Current vs. Input Voltage
(AAT3681A, AAT3681A-2, and AAT3681A-5 Only)
Input Voltage (V)
Trickle Charge Current (mA)
0
5
10
15
20
25
30
35
44.5 55.5 66.5
77
.5
RSET = 5.36kΩ
RSET = 8.06kΩ
RSET = 16.2kΩ
RSET = 31.6kΩ
Recharging Threshold Voltage vs. Temperature
(RSET = 8.06kΩ; AAT3681A, AAT3681A-1,
AAT3681A-2, and AAT3681A-4 Only)
Temperature (°C)
V
RCH
(V)
4.02
4.04
4.06
4.08
4.10
4.12
4.14
4.16
4.18
-50-25 0255075 100
Recharging Threshold Voltage vs. Temperature
(AAT3681A-4.1 and AAT3681A-5 Only)
Temperature (°C)
End Of Charge Voltage
Regulation (V)
-40-15 10 35 60 85
3.950
3.970
3.990
4.010
4.030
4.050
Shutdown Current vs. Supply Voltage
(RSET = 8.06kΩ)
Supply Voltage (V)
Shutdown Current (nA)
0
200
400
600
800
1000
1200
1400
1600
1800
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.
5
85°C
25°C-40°C
Input Enable High Voltage vs. Supply Voltage
(RSET = 8.06kΩ)
VIN (V)
V
IH_ENABLE
(V)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
4.04.5 5.05.5 6.06.5 7.07.5
-40°C
25°C85°C
Input Enable Low Voltage vs. Supply Voltage
(RSET = 8.06kΩ)
VIN (V)
V
IL_ENABLE
(V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
4.04.5 5.05.5 6.06.5 7.07.5
-40°C
25°C
85°C
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
9
Functional Description
The AAT3681A is a high performance battery charger
designed for single cell lithium-ion/polymer batteries
with up to 500mA of charge current from an external
power source. It is a stand-alone charging solution, with
just one external component required for complete func-
tionality. The AAT3681A precisely regulates battery
charge voltage and current for 4.2V lithium-ion/polymer
battery cells. The AAT3681A-5 regulates battery charge
voltage for 4.1V Lithium-ion/polymer battery cells.
The adapter/USB charge input constant current level can
be programmed up to 500mA for rapid charging applica-
tions. The AAT3681A/-1/-2/-4/-5 is rated for operation
from -40°C to +85°C. In the event of operating ambient
temperatures exceeding the power dissipation abilities of
the device package for a given constant current charge
level, the charge control will enter into thermal limit.
A status monitor output pin is provided to indicate the
battery charge state by directly driving one external
LED.
Device junction temperature and charge state are fully
monitored for fault conditions. In the event of an over-
voltage or over-temperature failure, the device will auto-
matically shut down, protecting the charging device,
control system, and the battery under charge.
Charging Operation
The AAT3681A has four basic modes for the battery
charge cycle: pre-conditioning/trickle charge; constant
current/fastcharge;constantvoltage;andchargetermi-
nation(seeFigure1).(AAT3681A-1andAAT3681A-4do
not have trickle charge.)
Functional Block Diagram
Charge
Control
Current
Compare
Reverse Blocking
CV/
Precharge
Constant
Current
ADP BAT
ISET
UVLO
Over-
Temperature
Protection
Charge
Status
STAT
GND
EN
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201883C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • November 19, 2012
Battery Preconditioning
Before the start of charging, the AAT3681A checks sev-
eral conditions in order to assure a safe charging envi-
ronment. The input supply must be above the minimum
operating voltage, or under-voltage lockout threshold
(VUVLO), for the charging sequence to begin. When these
conditions have been met and a battery is connected to
the BAT pin, the AAT3681A checks the state of the bat-
tery. If the cell voltage is below the preconditioning volt-
age threshold (VMIN), the charge control begins precon-
ditioning the cell. The battery preconditioning trickle
charge current is equal to the fast charge constant cur-
rentdividedby10.Forexample,iftheprogrammedfast
charge current is 300mA, then the preconditioning mode
(trickle charge) current will be 30mA. Cell precondition-
ing is a safety precaution for deeply discharged battery
cells and also aids in limiting power dissipation in the
pass transistor when the voltage across the device is at
the greatest potential.
Constant Current Charging
Battery cell preconditioning continues until the voltage
on the BAT pin exceeds the preconditioning voltage
threshold (VMIN). At this point, the AAT3681A begins the
constant current charging phase. The charge constant
current (ICH) amplitude is programmed by the user via
theRSET resistor. The AAT3681A remains in the constant
current charge mode until the battery reaches the con-
stant voltage regulation point, VCO(REG).
Constant Voltage Charging
The system transitions to a constant voltage charging
mode when the battery voltage reaches the constant
output voltage charge regulation threshold (VCO(REG)) dur-
ing the constant current fast charge phase. The regula-
tion voltage level is factory programmed to 4.2V
(±0.5%) for AAT3681A/-1/-2/-4 and 4.1 (±0.5%) for
AAT3681A-5. Charge current in the constant voltage
mode drops as the battery cell under charge reaches its
maximum capacity.
End of Charge Cycle Termination
and Recharge Sequence
When the charge current drops to 10% of the pro-
grammed fast charge current level in the constant volt-
age mode, the device terminates charging and goes into
a sleep state. The charger will remain in a sleep state
until the battery voltage decreases to a level below the
battery recharge voltage threshold (VRCH).
Consuming very low current in sleep state, the AAT3681A
minimizes battery drain when it is not charging. This
feature is particularly useful in applications where the
input supply level may fall below the battery charge or
under-voltage lockout level. In such cases where the
AAT3681A input voltage drops, the device will enter
sleep state and automatically resume charging once the
input supply has recovered from the fault condition.
Constant Current
Charge Phase
Preconditioning
Trickle Charge
Phase
Charge Complete Voltage
Constant Current Mode
Voltage Threshold
Regulated Current
Trickle Charge and
Termination Threshold
I = CC / 10
I = Max CC
Battery Recharge
Voltage Threshold
Battery Discharge
Constant Voltage
Charge Phase
Constant Voltage
Charge Phase
Figure 1: Current vs. Voltage Profile During Charging Phases.
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AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
11
System Operation Flow Chart
Power On Reset
Power Input
Voltage
VIN > VUVLO
Fault Conditions
Monitoring
OV, OT
Preconditioning
Test
VMIN > VBAT
Current Phase Test
VCO(REG)
> VBAT
Voltage Phase Test
IBAT > ITERM
No (AAT3681A,
AAT3681A-2,
AAT3681A-5)
No
Yes
No
Preconditioning
(Trickle Charge)
Constant
Current Charge
Mode
Constant
Voltage Charge
Mode
Yes
Yes
Yes
No
Charge Completed
Charge
Control
No (AAT3681A, AAT3681A-1,
AAT3681A-2, AAT3681A-4,
AAT3681A-5, AAT3681A-6)
Recharge Test
VRCH > VBAT
Yes
No
Shut Down Yes
Enable
Yes
No
No (AAT3681A-1,
AAT3681A-4)
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
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Application Information
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 AAT3681A 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 values for a
desired constant current charge level.
Adapter Input Charge Inhibit and Resume
TheAAT3681A has a UVLOandpoweronresetfeature
so that if the input supply to the ADP pin drops below the
UVLOthreshold,thecharger will suspendchargingand
shut down. When power is re-applied to the ADP pin or
theUVLOconditionrecovers,thesystemchargecontrol
will assess the state of charge on the battery cell and will
automatically resume charging in the appropriate mode
for the condition of the battery.
Enable / Disable
The AAT3681A provides an enable function to control the
charger IC on and off. The EN pin functions as follows on
thevariousAAT3681Aoptions:
AAT3681A, AAT3681A-1, AAT3681A-4, and
AAT3681A-5: The enable (EN) pin is internally pulled
downthrougha6MΩresistor.Whenpulledtoalogichigh
level, the AAT3681A is enabled. When left open or pulled
to a logic low level, the AAT3681A will be shut down and
forced into the sleep state.
AAT3681A-2: The enable (EN) pin is internally pulled
down. When left open or pulled to a logic low level, the
AAT3681A-2 is enabled. When pulled to a logic high
level, the AAT3681A-2 will be shut down and forced into
the sleep state.
Charging will be halted regardless of the battery voltage
or charging state. When the device 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 on the BAT pin.
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 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-
stant current levels from 15mA to 500mA may be set by
selecting the appropriate resistor value from Table 1.
Nominal
ICHARGE (mA)
Set Resistor
Value (kW)
500 3.24
450 3.57
400 4.12
350 4.64
300 5.36
250 6.49
200 8.06
150 10.7
100 16.2
50 31.6
40 38.3
30 53.6
20 78.7
15 105
Table 1: RSET Values.
RSET (kΩ)
ICH (mA)
1
10
100
1000
110 100 1000
Constant Charging Current
vs. Set Resistor Values
Figure 2: Constant Charging Current
vs. Set Resistor Values.
Protection Circuitry
Over-Voltage Protection
An over-voltage event is defined as a condition where
the voltage on the BAT pin exceeds the maximum bat-
tery charge voltage and is set by the over-voltage pro-
tection threshold (VOVP). If an over-voltage condition
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AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
13
occurs, the AAT3681A charge control will shut down the
device until the voltage on the BAT pin drops below VOVP
.
The AAT3681A will resume normal charging operation
after the over-voltage condition is removed.
Over-Temperature Shutdown
The AAT3681A has a thermal protection control circuit
which will shut down charging functions should the inter-
nal die temperature exceed the preset thermal limit
threshold.Oncetheinternaldietemperaturefallsbelow
the thermal limit, normal operation will resume the pre-
vious charging state.
Charge Status Output
The AAT3681A provides battery charge status via a sta-
tus 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 the following condi-
tions:
Event Description Status
No battery charging activity OFF
Battery charging via adapter or USB port ON
Charging completed OFF
Table 2: LED Status Indicator.
The LED should be biased with as little current as neces-
sarytocreatereasonableillumination;therefore,abal-
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. A 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:
(V
ADP
-
V
F(LED)
)
R
1
= I
LED
Example:
(5.5V
- 2.0
V)
R
1
==
1.75kΩ
2mA
Note:RedLEDforwardvoltage(VF) is typically 2.0V @
2mA.
Thermal Considerations
The AAT3681A is offered in a SC70JW-8 package which
can provide up to 687mW of power dissipation when it
is properly bonded to a printed circuit board and has a
maximum thermal resistance of 160°C/W. Many consid-
erations 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 charger IC will also
have an effect on the thermal limits of a battery charg-
ing application. The maximum limits that can be expect-
ed for a given ambient condition can be estimated by the
following discussion.
First,themaximumpowerdissipationforagivensitua-
tionshouldbecalculated:
J(MAX)
A
P
D(MAX)
= θ
JA
Where:
PD(MAX) = Maximum Power Dissipation (W)
qJA=PackageThermalResistance(°C/W)
TJ(MAX) = Maximum Device Junction Temperature (°C)
[135°C]
TA = Ambient Temperature (°C)
Figure3showstherelationshipofmaximumpowerdis-
sipation and ambient temperature of AAT3681A.
TA (°C)
PD(MAX) (mW)
0
200
400
600
800
1000
020406080 100
Figure 3: Maximum Power Dissipation.
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
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Next, the power dissipation can be calculated by the fol-
lowingequation:
PD = [(VIN - VBAT) · ICH + (VIN · IOP)]
Where:
PD = Total Power Dissipation by the Device
VIN = Input 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.
(P
D(MAX)
-
V
IN
·
I
OP
)
V
IN
- V
BAT
I
CH(MAX)
=
(T
J(MAX) -
T
A
)
θ
JA
V
IN
- V
BAT
I
CH(MAX)
=
-
V
IN
·
I
OP
In general, the worst condition is the greatest voltage
drop across the charger IC, when battery voltage is
charged up to the preconditioning voltage threshold.
Figure4showsthemaximumchargecurrentindifferent
ambient temperatures without PCB thermal enhance-
ments.
VIN (V)
ICH(MAX) (mA)
0
50
100
150
200
250
300
350
400
450
500
4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7
TA = 85°CTA = 60°C
TA = 25°C
TA = 45°C
Figure 4: Maximum Charging Current Before
Thermal Cycling Becomes Active.
Capacitor Selection
Input Capacitor
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
AAT3681A 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.
Output Capacitor
TheAAT3681Aonlyrequiresa1µFceramiccapacitor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
AAT3681A 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.
Printed Circuit Board
Layout Considerations
For the best results, it is recommended to physically
place the battery pack as close as possible to the
AAT3681A BAT pin. To minimize voltage drops on the
PCB, keep the high current carrying traces adequately
wide.RefertotheAAT3681Aevaluationboardforagood
layoutexample(seeFigures5and6).
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AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
15
Figure 5: AAT3681A Evaluation Board Figure 6: AAT3681A Evaluation Board
Top Side Layout. Bottom Side Layout.
RED LED
D1 R1
1K
10µF
C1 2.2µF
C2
V
IN(ADP)
V
BAT
8.06K
R8
JP2
JP1
0Ω
EN
1
ISET
2
BAT
3
ADP
4STAT 5
GND 6
GND 7
GND 8
AAT3681A
U1 (SC70JW-8)
Figure 7: AAT3681A Evaluation Board Schematic Diagram.
Component Part Number Description Manufacturer
U1 AAT3681AIJS-T1 USB/ADPBatteryCharger;SC70JW-8Package Skyworks
R1 ChipResistor 1kW,5%,1/4W;0603
VishayR8 ChipResistor 8.06kW,1%,1/4W;0805
JP1 ChipResistor 0W,5%,1/4W;0603
C1 GRM21BR61A106KE19L Ceramic10µF10V10%X5R0805 Murata
C2 GRM21BR71A225KA01L Ceramic2.2µF10V10%X7R0805
JP2 PRPN401PAEN ConnectingHeader,2mmZip Sullins Electronics
LED1 CMD15-21SRC/TR8 RedLED;1206 Chicago Miniature Lamp
Table 3: AAT3681A Evaluation Board Bill of Materials.
AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
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Ordering Information
Trickle Charge Enable Package Marking1Part Number (Tape and Reel)2
Yes ActiveHigh SC70JW-8 E4XYY AAT3681AIJS-4.1-T1
Yes ActiveHigh SC70JW-8 UTXYY AAT3681AIJS-4.2-T1
No ActiveHigh SC70JW-8 UEXYY AAT3681AIJS-4.2-1-T1
Yes Active Low SC70JW-8 VSXYY AAT3681AIJS-4.2-2-T1
No ActiveHigh SC70JW-8 A9XYY AAT3681AIJS-4.2-4-T1
Yes ActiveHigh SC70JW-8 F2XYY AAT3681AIJS-4.1-5-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
SC70JW-8
0.225 ± 0.075
0.45 ± 0.10
0.05 ± 0.05
2.10 ± 0.30
2.00 ± 0.20
7° ± 3°4° ± 4°
1.75 ± 0.10
0.85 ± 0.15
0.15 ± 0.05
1.10 MAX
0.100
2.20 ± 0.20
0.048REF
0.50 BSC 0.50 BSC 0.50 BSC
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
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AAT3681A
DATA SHEET
500mA USB Port or AC Adapter Li-Ion/Polymer Battery Charger
17
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Sky-
works may change its documentation, products, services, specications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
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