General Description
The AAT3685 BatteryManager™ is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. This device is a highly
integrated single cell lithium-ion/polymer battery
charger IC designed to operate with USB port or
line adapter inputs. It requires the minimum number
of external components.
The AAT3685 precisely regulates battery charge volt-
age and current for 4.2V lithium-ion/polymer battery
cells. Regardless of the type of input power source
(USB or adapter), the AAT3685 can be programmed
for two separate constant current charge levels up to
1A. An optional Charge Reduction Loop is built in to
allow users to charge the battery with available cur-
rent from the charge supply, while keeping the port
voltage regulated.
Battery temperature and charge state are fully
monitored for fault conditions. In the event of an
over-voltage or over-temperature failure, the
device will automatically shut down, thus protecting
the charging device, control system, and the bat-
tery under charge. Status monitor output pins are
provided to indicate the battery charge status by
directly driving two external LEDs. A serial interface
output is available to report any one of 14 various
status states to a microcontroller.
The AAT3685 is available in a Pb-free, thermally-
enhanced, space-saving 12-pin 3x3mm TDFN
package and is rated over the -40°C to +85°C tem-
perature range.
Features
• Adapter or USB Charger
— Programmable up to 1A Max
• 4.0V to 5.5V Input Voltage Range
• High Level of Integration With Internal:
— Charging Device
— Reverse Blocking Diode
— Current Sensing
• Automatic Recharge Sequencing
• Charge Reduction Loop
• Battery Temperature Monitoring
• Full Battery Charge Auto Turn-Off
• Over-Voltage Protection
• Emergency Thermal Protection
• Power On Reset and Soft Start
• Serial Interface Status Reporting
• 12-Pin 3x3mm TDFN Package
Applications
• Cellular Telephones
• Digital Still Cameras
• Hand-Held PCs
• MP3 Players
• Personal Data Assistants (PDAs)
• Other Lithium-Ion/Polymer Battery-Powered
Devices
AAT3685
Lithium-Ion/Polymer Battery Charger
Typical Application
AAT3685
C2
10µF
BATT-
TEMP
A
dapter or USB Input
Battery Pack
Serial Data
ADP/USB
PWRSEL
GND
TS
BAT
BATT+
Input Hi/Lo Select
STAT1
RSETH
SETH
RSETL
SETL
CHREN
STAT2
DATA
Enable
3685.2006.02.1.2 1
BatteryManager™
Pin Descriptions
Pin Configuration TDFN33-12
(Top View)
A
DP/USB
BAT
GND
1
CHR
EN
TS
SETH
SETL
PWRSEL
STAT1
STAT2
DATA
2
3
4
5
6
12
11
10
9
8
7
Pin # Name Type Function
1 ADP/USB In Line adapter or USB power supply input.
2 BAT In/Out Battery charging and sensing.
3 GND Ground Ground connection.
4 CHR In/Out Resistor divider to set USB voltage regulation for charge reduction mode.
Leave this pin open for default 4.5V USB regulation point. Tie to ADP/USB
pin to disable this function.
5 EN In Enable pin. Logic high enables the IC.
6 TS In/Out Connect to 10kΩNTC thermistor.
7 DATA In/Out Status report to microcontroller via serial interface, open-drain.
8 STAT2 Out Battery charge status indicator pin to drive an LED: active low, open-drain.
9 STAT1 Out Battery charge status indicator pin to drive an LED: active low, open-drain.
10 PWRSEL In When ADP/USB is present, use this pin to toggle between SETH and SETL
charging levels.
11 SETL In/Out Connect resistor here to set charge current for low-current port.
12 SETH In/Out Connect resistor here to set charge current for high-current port.
EP Exposed paddle (bottom); connect to GND directly beneath package.
AAT3685
Lithium-Ion/Polymer Battery Charger
23685.2006.02.1.2
Absolute Maximum Ratings1
Thermal Information2
Symbol Description Value Units
θJA Maximum Thermal Resistance (3x3mm TDFN) 50 °C/W
PDMaximum Power Dissipation 2.0 W
Symbol Description Value Units
VPADP/USB Input Voltage, <30ms, Duty Cycle <10% -0.3 to 7.0 V
VPADP/USB Input Voltage, Continuous -0.3 to 6.0 V
VNBAT, PWRSEL, SETH, SETL, STAT1, STAT2, DATA, TS, CHR, EN -0.3 to VVP + 0.3 V
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads) 300 °C
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 3
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
Electrical Characteristics1
VADP = 5V, TA= -25°C to +85°C, unless otherwise noted. Typical values are at TA= 25°C.
Symbol Description Conditions Min Typ Max Units
Operation
ADP/USB Input Voltage Range 4.0 5.5 V
VUVLO
Under-Voltage Lockout Rising Edge 3.0 V
Under-Voltage Lockout Hysteresis 150 mV
IOP Operating Current CC Charge Current = 500mA 0.75 1.5 mA
ISLEEP Sleep Mode Current VBAT = 4.25V 0.3 1.0 µA
ILeakage
Reverse Leakage Current from VBAT = 4V, ADP/USB Pin 1.0 µA
BAT Pin Open
Voltage Regulation
VBAT_EOC1End of Charge Voltage Accuracy 4.158 4.2 4.242 V
∆VBAT/VBAT EOC Voltage Tolerance 0.5 %
VMIN Preconditioning Voltage Threshold 2.8 3.0 3.15 V
VRCH Battery Recharge Voltage Threshold VBAT_EOC - 0.1 V
VADP/USB_CHR Charge Reduction Regulation No Connection on CHR Pin 4.3 4.5 4.64 V
VCHR CHR Pin Voltage Accuracy 1.9 2.0 2.1 V
Current Regulation
ICH Charge Current 50 1000 mA
∆ICH/ICH
Charge Current Regulation 10 %
Tolerance
VSETH SETH Pin Voltage CC Mode 2.0 V
VSETL SETL Pin Voltage CC Mode 2.0 V
KIUH Current Set Factor: ICHARGE/ISETH 2000
KIUL Current Set Factor: ICHARGE/ISETL 2000
Charging Devices
RDS(ON)U
Charging MOSFET Transistor VIN = 5.5V 0.4 0.5 0.65 Ω
On Resistance
AAT3685
Lithium-Ion/Polymer Battery Charger
43685.2006.02.1.2
1. The AAT3685 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C
temperature range is guaranteed by design.
Electrical Characteristics1
VADP = 5V, TA= -25°C to +85°C, unless otherwise noted. Typical values are at TA= 25°C.
Symbol Description Conditions Min Typ Max Units
Logic Control / Protection
VPWRSEL(H) Input High Threshold 1.6 V
VPWRSEL(L) Input Low Threshold 0.4 V
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 8.0 mA
VOVP Over-Voltage Protection Threshold 4.4 V
Pre-Charge Current ITK/ICHG
For SETH Mode 10 %
For SETL Mode 50
Charge Termination Threshold Current For SETH Mode 7.5 %
ITERM/ICHG
Charge Termination Threshold Current For SETL Mode 35 %
ITERM/ICHG
ITS Current Source from TS Pin 70 80 90 µA
TS1 TS Hot Temperature Fault Threshold 310 330 350 mV
Hysteresis 15
TS2 TS Cold Temperature Fault Threshold 2.2 2.3 2.4 V
Hysteresis 10 mV
I_DATA DATA Pin Sink Current DATA Pin is Active Low State 3.0 mA
VDATA(H) Input High Threshold 1.6 V
VDATA)(L) Input Low Threshold 0.4 V
SQPULSE Status Request Pulse Width Status Request 200 ns
tPERIOD System Clock Period 50 µs
fDATA Data Output Frequency 20 kHz
TOVSD Over-Temperature Shutdown Threshold 145 °C
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 5
1. The AAT3685 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C
temperature range is guaranteed by design.
Typical Characteristics
Preconditioning Charge Current vs. Temperature
(SETH; SETH = 3.83kΩ
Ω
)
Temperature (°C)
ICH (mA)
80
90
100
110
120
-50 -25 0 25 50 75 100
Preconditioning Threshold
Voltage vs. Temperature
Temperature (°C)
VMIN (V)
2.95
2.96
2.97
2.98
2.99
3.00
3.01
3.02
3.03
3.04
3.05
-50 -25 0 25 50 75 100
End of Charge Voltage vs. Temperature
Temperature (°C)
VBAT (V)
4.158
4.179
4.200
4.221
4.242
-50 -25 0 25 50 75 100
Recharge Voltage vs. Temperature
Temperature (°C)
VRCH (V)
4.040
4.050
4.060
4.070
4.080
4.090
4.100
4.110
4.120
4.130
4.140
-50 -25 0 25 50 75 100
Battery Voltage vs. Supply Voltage
Supply Voltage (V)
VBAT (V)
4.158
4.179
4.200
4.221
4.242
4.5 4.75 5 5.25 5.5
IFASTCHARGE vs. RSET
RSET (kΩ)
IFASTCHARGE (mA)
10
100
1000
10000
1 10 100 1000
SETL
SETH
AAT3685
Lithium-Ion/Polymer Battery Charger
63685.2006.02.1.2
Typical Characteristics
Fast Charge Current vs. Supply Voltage
(SETH; SETH = 3.83kΩ
Ω
)
Supply Voltage (V)
ICH (mA)
0
200
400
600
800
1000
1200
4.40 4.50 4.60 4.70 4.80 4.90 5.0
0
0°C
25°C
70°C
Fast Charge Current vs. Supply Voltage
(SETL; SETL = 40.2kΩ
Ω
)
Supply Voltage (V)
ICH (mA)
0
20
40
60
80
100
120
4 4.5 5.5 6.556
VBAT = 3.3V
VBAT = 3.5V
VBAT = 3.9V
Fast Charge Current vs. Supply Voltage
(SETH; SETH = 3.83kΩ
Ω
)
Supply Voltage (V)
ICH (mA)
0
200
400
600
800
1000
1200
4 4.25 4.5 4.75 5 5.25 5.5 5.75 6
VBAT = 3.3V
VBAT = 3.9V
VBAT = 3.5V
Charging Current vs. Battery Voltage
(SETL; SETL = 40.2kΩ
Ω
)
Battery Voltage (V)
ICH (mA)
0
20
40
60
80
100
120
2.5 3 3.5 4 4.
5
Charging Current vs. Battery Voltage
(SETH; SETH = 3.83kΩ)
Battery Voltage (V)
ICH (mA)
0
200
400
600
800
1000
1200
2.5 3 3.5 4 4.5
Fast Charge Current vs. Temperature
(SETH; SETH = 3.83kΩ
Ω
)
Temperature (°C)
ICH (mA)
900
920
940
960
980
1000
1020
1040
1060
1080
1100
-50 -25 0 25 50 75 100
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 7
Typical Characteristics
Charge Current vs. Time
(SETH; SETH = 3.83kΩ
Ω
)
Time (sec)
VBUS
(400mV/div)
Charge
Current
(400mA/div)
Peripheral
Current
Consumption
(400mA/div)
01 23 456 7 8910
Charge Reduction
Mode Activated
Supply Current vs. SETH Resistor
SETH Resistor (kΩ
Ω
)
IQ (mA)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
1 10 100 100
0
Constant Current
Pre-Conditioning
VIL vs. Supply Voltage
PWRSEL (Falling)
Supply Voltage (V)
VIL (V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
-40°C +25°C
+85°C
VIH vs. Supply Voltage
PWRSEL (Rising)
Supply Voltage (V)
VIH (V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
-40°C +25°C
+85°C
VIL vs. Supply Voltage
EN Pin (Falling)
Supply Voltage (V)
VIL (V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
-40°C +25°C
+85°C
VIH vs. Supply Voltage
EN Pin (Rising)
Supply Voltage (V)
VIH (V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
4.2 4.4 4.6 4.8 5 5.2 5.4 5.6 5.8 6
-40°C +25°C
+85°C
AAT3685
Lithium-Ion/Polymer Battery Charger
83685.2006.02.1.2
Typical Characteristics
Temperature Sense Output
Current vs. Temperature
Temperature (°
°
C)
TS Pin CUrrent (µA)
72
74
76
78
80
82
84
86
88
-50 -25 0 25 50 75 100
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 9
Functional Block Diagram
Charge
Control
Current
Compare
Reverse Blocking
CV/
Precharge
A
DP/USB
PWRSEL
Constant
Current
BA
T
UVLO
Over-
Temperature
Protect
Charge
Status
STAT2
STAT1
TS
Window
Comparator
80µA
SETH
SETL
Serial
Data
DATA
GND
Charge
Reduction
Loop
CHR
EN
IC enable
AAT3685
Lithium-Ion/Polymer Battery Charger
10 3685.2006.02.1.2
Functional Description
The AAT3685 is a highly integrated single cell lithi-
um-ion/polymer battery charger IC designed to
operate from adapter or USB port VBUS supplies,
while requiring a minimum number of external
components. The device precisely regulates bat-
tery charge voltage and current for 4.2V lithium-
ion/polymer battery cells.
The AAT3685 is specifically designed for being
powered from a USB port VBUS supply, but it can
also be powered from any input voltage source
capable supplying 4.5V to 5.5V for loads up to 1A.
The AAT3685 constant charge current can be
externally programmed for two levels, SETH and
SETL, for maximum constant current charge levels
up to 1A. The SETH/L mode has an automatic
Charge Reduction Loop control to allow users to
charge the battery with limited available current
from a port while maintaining the regulated port
voltage. This system assures the battery charge
function will not overload the port while charging if
other system demands also share power with the
respective port supply.
Status monitor output pins are provided to indicate
the battery charge status by directly driving two
external LEDs. A serial interface output is available
to report 14 various charge states to a system
microcontroller.
Battery temperature and charge state are fully
monitored for fault conditions. In the event of an
over-voltage or over-temperature failure, the
device will automatically shut down, thus protecting
the charging device, control system, and the bat-
tery under charge. In addition to internal charge
controller thermal protection, the AAT3685 also
provides a temperature sense feedback function
(TS pin) from the battery to shut down the device in
the event the battery exceeds its own thermal limit
during charging. All fault events are reported to the
user either by the simple status LEDs or via the
DATA pin function.
Charging Operation
The AAT3685 has four basic modes for the battery
charge cycle and is powered from the input: pre-con-
ditioning/trickle charge; constant current/fast charge;
constant voltage; and end of charge. For reference,
Figure 1 shows the current versus voltage profile
during charging phases.
Battery Preconditioning
Before the start of charging, the AAT3685 checks
several conditions in order to assure a safe charging
environment. The input supply must be above the
minimum operating voltage, or under-voltage lockout
threshold (VUVLO), for the charging sequence to
begin. In addition, the cell temperature, as reported
by a thermistor connected to the TS pin from the bat-
tery, must be within the proper window for safe
charging. When these conditions have been met and
a battery is connected to the BAT pin, the AAT3685
checks the state of the battery. If the cell voltage is
below the Preconditioning Voltage Threshold (VMIN),
the AAT3685 begins preconditioning the cell.
The battery preconditioning trickle charge current
is equal to the fast charge constant current divided
by 10. For example, if the programmed fast charge
current is 500mA, then the preconditioning mode
(trickle charge) current will be 50mA. Cell precon-
ditioning is a safety precaution for a deeply dis-
charged battery and also aids in limiting power dis-
sipation in the pass transistor when the voltage
across the device is at the greatest potential.
Fast Charge / Constant Current Charging
Battery cell preconditioning continues until the volt-
age on the BAT pin exceeds the Preconditioning
Voltage Threshold (VMIN). At this point, the AAT3685
begins the constant current fast charging phase.
The fast charge constant current (ICC) amplitude is
determined by the selected charge mode SETH or
SETL and is programmed by the user via the RSETH
and RSETL resistors. The AAT3685 remains in con-
stant current charge mode until the battery reaches
the voltage regulation point, VBAT.
Constant Voltage Charging
The system transitions to a constant voltage charg-
ing mode when the battery voltage reaches output
charge regulation threshold (VBAT) during the con-
stant current, fast charge phase. The regulation
voltage level is factory programmed to 4.2V ( 1%).
The 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 7.5% 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).
When the input supply is disconnected, the charg-
er will also automatically enter power-saving sleep
mode. Only consuming an ultra-low 0.3µA in sleep
mode, the AAT3685 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 AAT3685 input volt-
age drops, the device will enter the sleep mode and
automatically resume charging once the input sup-
ply has recovered from its fault condition.
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 11
Figure 1: Current vs. Voltage Profile During Charging Phases.
Constant Current
Charge Phase
Constant Voltage
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
System Operation Flow Chart
UVLO
Battery
Temperature Monitor
V
TS1
< TS < V
TS2
Preconditioning Test
Current Phase Test
V
CH
>V
BAT
V
MIN
>V
BAT
Voltage Phase Test
V
P
> V
UVLO
Shut Down
Mode
Shut Down
Mode
No
No
Yes
Yes Low Current
Conditioning
Charge
Low Current
Conditioning
Charge
Battery
Temp. Fault
Battery
Temperature
Fault
No
No
Current
Charging
Mode
Current
Charging
Mode
Yes
Voltage
Charging
Mode
Voltage
Charging
Mode
I
BAT
> I
MIN
No
Yes
No
Switch
On
Switch
On
YesYes
Input Detect
PWRSEL > 0
Charge
Completed
Charge
Completed
Recharge Test
V
RCH
> V
BAT
Yes
No
Power On
Reset
Power On
Reset
Sleep
Mode
Sleep
Mode
Yes
USB High
Current Loop
SETH
Current Loop
USB Low
Current Loop
SETL
Current Loop
No
Yes No
Fault
Conditions Monitor
OV, OT
Yes
Port Voltage Test
V
P
<4.5V
USB Voltage
Regulation
Enable
Input Voltage
Regulation
Enable
USB Loop
Current
Reduction in USB
Charging Mode
Charge
Current
Reduction
No
USB Power
Input Power
AAT3685
Lithium-Ion/Polymer Battery Charger
12 3685.2006.02.1.2
Application Information
USB System Power Charging
The USB charge mode provides two programma-
ble fast charge levels up to 1A for each, SETH and
SETL. The SETH or SETL modes may be exter-
nally selected by the select pin (PWRSEL). When
the PWRSEL pin is connected to a logic high level,
the SETH level will be active. Conversely, when
PWRSEL is pulled to a logic low level (ground), the
SETL level will be used for fast charging. These
two charge levels may be user programmed to any
level between 50mA and 1A by selecting the appro-
priate resistor values for RSETH and RSETL. Refer to
Table 1 for recommended RSETH and RSETL values
for the desired input constant current charge levels.
Charge Reduction
In many instances, product system designers do
not know the real properties of a potential port to be
used to supply power to the battery charger.
Typical powered USB ports commonly found on
desktop and notebook PCs should supply up to
500mA. In the event a port being used to supply
the charger is unable to provide the programmed
fast charge current, or if the system under charge
must also share supply current with other func-
tions, the AAT3685 will automatically reduce USB
fast charge current to maintain port integrity and
protect the host system.
The charge reduction system becomes active when
the voltage on the input falls below the charge
reduction threshold (VADP/USB_CHR), which is typical-
ly 4.5V. Regardless of which charge function is
selected (SETH or SETL), the charge reduction
system will reduce the fast charge current level in a
linear fashion until the voltage sensed on the input
recovers above the charge reduction threshold volt-
age. The charge reduction threshold (VADP/USB_CHR)
may be externally set to a value lower than 4.5V by
placing a resistor divider network between VADP/USB
and ground with the center connected to the CHR
pin. The charge reduction feature may be disabled
by connecting a 10kΩresistor from the CHR pin
directly to the ADP/USB input pin.
The following equation may be used to approximate
a USB charge reduction threshold below 4.5V:
Eq. 1:
where R11/R12 << 1MΩ.
VADP/USB_CHR = 2.0V ÷ R12
R12 + R11
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 13
Table 1: Recommended RSET Values.
Figure 2: Internal Equivalent
Circuit for the CHR Pin.
1.025M
825k
R11
R12
V
CHR
= 2.0
V
V
ADP/USB
ADP/USB
CHR
SETH SETL SETH SETL
ICC RSET (kΩΩ)R
SET (kΩΩ)I
CC RSET (kΩΩ)R
SET (kΩΩ)
50 86.6 86.6 500 8.06 8.06
75 57.6 57.6 600 6.65 6.65
100 42.2 42.2 700 5.62 5.62
200 21.0 20.5 800 4.87 4.87
300 13.7 13.7 900 4.32 4.32
400 10.2 10.2 1000 3.83 3.83
Input Charge Inhibit and Resume
The AAT3685 UVLO and power on reset feature
will function when the input pin voltage level drops
below the UVLO threshold. At this point, the charg-
er will suspend charging and shut down. When
power is re-applied to the ADP/USB pin or the
UVLO condition recovers, the system charge con-
trol 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.
Single Path Charging from a Line Adapter or
USB Source
Most USB charging applications limit charging cur-
rent to 500mA due to the limitations of a USB port
as a power source. The AAT3685 is capable of,
and may be programmed for, constant current
charge levels up to 1A. Thus, charging operation
is not just restricted to use with USB port supplies.
Any power source may be used within the operat-
ing voltage limits as specified in the Electrical
Characteristics section of this datasheet. This
makes the AAT3685 perfect for applications that
only have one input path, but may access either a
line adapter source or a USB port supply.
In order to fully utilize the power capacity from a line
adapter or USB port supply, program the SETH
charge rate according to the highest charging cur-
rent capacity of the two possible sources, providing
that neither supply exceeds 1A. A lower charge
level may be set with the SETL charge rate and
selection of the higher or lower charge rate is con-
trolled via the PWRSEL function. If the pro-
grammed charge rate is greater than the current
source capacity, there is little danger of system fail-
ure because the AAT3685 charge reduction loop
will activate to automatically reduce the charging
current and maintain a supply voltage set by the
CHR threshold. If the input supply is incapable of
maintaining an input voltage greater than the under-
voltage lockout level of the AAT3685, the charge
control will suspend charging until the source sup-
ply is capable of supplying the minimum input cur-
rent to charge. At this point, the AAT3685 will auto-
matically resume charging in the appropriate mode
based on the battery cell voltage. In case of an
over-temperature condition with a high charge cur-
rent and large input-to-battery voltage difference,
the device will cycle from charging to thermal shut-
down and re-charge after temperature drops suffi-
ciently, until the battery is charged to 4.2V.
Enable / Disable
The AAT3685 provides an enable function to con-
trol the charger IC on and off. The enable (EN) pin
is an active high. When pulled to a logic low level,
the AAT3685 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.
Programming Charge Current
The fast charge constant current charge level for the
ADP/USB input is programmed with set resistors
placed between the SETH and SETL pins 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 resistors used. For
this reason, 1% tolerance metal film resistors are
recommended for programming the desired con-
stant current level.
The fast charge constant current charge control
provides for two current set levels, SETH and
SETL. The PWRSEL pin is used to select the high
or low charge current levels. When the PWRSEL
pin is pulled to a voltage level above the VPWRSEL(H)
threshold, the SETH current level will be selected.
Conversely, this pin should be pulled below the
VPWRSEL(L) to enable the SETL charge level. These
two charge levels may be set to any level between
50mA and 1A, depending upon the system design
requirements for a given charge application. Refer
to Table 1 and Figure 3 for recommended RSETH
and RSETL values.
AAT3685
Lithium-Ion/Polymer Battery Charger
14 3685.2006.02.1.2
Figure 3: IFASTCHARGE vs. RSET.
Protection Circuitry
Over-Voltage Protection
An over-voltage event is defined as a condition
where the voltage on the BAT pin exceeds the
maximum battery charge voltage and is set by the
over-voltage protection threshold (VOVP). If an
over-voltage condition occurs, the AAT3685 charge
control will shut down the device until voltage on
the BAT pin drops below the over-voltage protec-
tion threshold (VOVP). The AAT3685 will resume
normal charging operation after the over-voltage
condition is removed. During an over-voltage
event, the STAT LEDs will report a system fault; the
actual fault condition may also be read via the
DATA pin signal.
Over-Temperature Shutdown
The AAT3685 has a thermal protection control cir-
cuit which will shut down charging functions should
the internal die temperature exceed the preset
thermal limit threshold.
Battery Temperature Fault Monitoring
In the event of a battery over-temperature condi-
tion, the charge control will turn off the internal pass
device and report a battery temperature fault on the
DATA pin function. The STAT LEDs will also dis-
play a system fault. After the system recovers
from a temperature fault, the device will resume
charging operation.
The AAT3685 checks battery temperature before
starting the charge cycle, as well as during all
stages of charging. This is accomplished by moni-
toring the voltage at the TS pin. This system is
intended for use negative temperature coefficient
(NTC) thermistors which are typically integrated into
the battery package. Most commonly used NTC
thermistors used in battery packs are approximate-
ly 10kΩat room temperature (25°C). The TS pin
has been specifically designed to source 80µA of
current to the thermistor. The voltage on the TS pin
that results from the resistive load should stay with-
in a window from 335mV to 2.32V. If the battery
becomes too hot during charging due to an internal
fault, the thermistor will heat up and reduce in value,
thus pulling the TS pin voltage lower than the TS1
threshold, and the AAT3685 will halt charging and
signal the fault condition. If the use of the TS pin
function is not required by the system, it should be
terminated to ground using a 10kΩresistor.
Battery Charge Status Indication
The AAT3685 indicates the status of the battery
under charge with two different systems. First, the
device has two status LED driver outputs. These
two LEDs can indicate simple functions such as no
battery charge activity, battery charging, charge
complete, and charge fault. The AAT3685 also
provides a bi-directional data reporting function so
that a system microcontroller may interrogate the
DATA pin and read any one of 14 system states.
Status Indicator Display
Simple system charging status may be displayed
using one or two LEDs in conjunction with the
STAT1 and STAT2 pins on the AAT3685. These
two pins are simple switches to connect the display
LED cathodes to ground. It is not necessary to use
both display LEDs if a user simply wants to have a
single lamp to show "charging" or "not charging."
This can be accomplished by just using the STAT1
pin and a single LED. Using two LEDs and both
STAT pins simply gives the user more information
for charging states. Refer to Table 2 for LED dis-
play definitions.
RSET (kΩ)
IFASTCHARGE (mA)
10
100
1000
10000
1 10 100 1000
SETL
SETH
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 15
The LED anodes should be connected to VUSB.
The LEDs should be biased with as little current as
necessary to create reasonable illumination; there-
fore, a ballast resistor should be placed between
each of the LED cathodes and the STAT1/2 pins.
LED current consumption will add to the over-ther-
mal power budget for the device package, hence it
is recommended to keep the LED drive current to a
minimum. 2mA should be sufficient to drive most
low-cost green, red, or multi-color LEDs. It is not
recommended to exceed 8mA for driving an indi-
vidual status LED.
The required ballast resistor value can be estimat-
ed using the following formulas:
Eq. 2:
Example:
Note: Red LED forward voltage (VF) is typically
2.0V @ 2mA.
Table 2 shows the four status LED display conditions.
Digital Charge Status Reporting
The AAT3685 has a comprehensive digital data
reporting system by use of the DATA pin feature.
This function can provide detailed information
regarding the state of the charging system. The
DATA pin is a bi-directional port which will read
back a series of data pulses when the system
microcontroller asserts a request pulse. This sin-
gle strobe request protocol will invoke one of 14
possible return pulse counts in which the micro-
controller can look up based on the serial report
shown in Table 3.
The DATA pin function is active low and should nor-
mally be pulled high to VUSB. This data line may
also be pulled high to the same level as the high
state for the logic I/O port on the system microcon-
troller. In order for the DATA pin control circuit to
generate clean sharp edges for the data output and
to maintain the integrity of the data timing for the
system, the pull-up resistor on the data line should
be low enough in value so that the DATA signal
returns to the high state without delay. If the value
of the pull-up resistor used is too high, the strobe
pulse from the system microcontroller may exceed
the maximum pulse time and the DATA output con-
trol could issue false status reports. A 1.5kΩresis-
tor is recommended when pulling the DATA pin
high to 5.0V at the VUSB input. If the data line is
pulled high to a voltage level less than 5.0V, the
pull-up resistor may be calculated based on a rec-
ommended minimum pull-up current of 3mA. Use
the following formula:
Eq. 3:
V
PULL-UP
R
PULL-UP
≤3mA
(5.0V
- 2.0
V)
R
B(STAT1)
= = 1.5kΩ
2mA
(V
USB -
V
F(LED)
)
R
B(STAT1/2)
= I
LED(STAT1/2)
AAT3685
Lithium-Ion/Polymer Battery Charger
16 3685.2006.02.1.2
Table 2: LED Display Status Conditions.
Event Description STAT1 STAT2
Charge Disabled or Low Supply Off Off
Charge Enabled Without Battery Flash1Flash1
Battery Charging On Off
Charge Completed Off On
Fault On On
1. Flashing rate depends on output capacitance.
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 17
Table 3: Serial Data Report Table.
Figure 4: Data Pin Application Circuit.
AAT3685
Status
Control
1.8V to 5.0V
DATA Pin
R
PULL_UP
µP GPIO
Port
GPIO
IN
IN
OUT
OUT
N DATA Report Status
1 Chip Over-Temperature Shutdown
2 Battery Temperature Fault
3 Over-Voltage Turn Off
4 Not Used
5 Not Used
6 Not Used
7 Not Used
8 Not Used
9 Not Used
10 Not Used
11 Not Used
12 Not Used
13 SETH Battery Condition Mode
14 SETH Charge Reduction in Constant Current Mode
15 SETH Constant Current Mode
16 SETH Constant Voltage Mode
17 SETH End of Charging
18 SETL Battery Condition Mode
19 SETL Charge End of Charging Reduction in Constant Current Mode
20 SETL Constant Current Mode
21 SETL Constant Voltage Mode
22 SETL End of Charging
23 Data Report Error
Data Timing
The system microcontroller should assert an active
low data request pulse for minimum duration of
200ns; this is specified by TLO(DATA). Upon sensing
the rising edge of the end of the data request pulse,
the AAT3685 status data control will reply the data
word back to the system microcontroller after a
delay specified by the data report time specification
TDATA(RPT). The period of the following group of data
pulses will be specified by the TDATA specification.
AAT3685
Lithium-Ion/Polymer Battery Charger
18 3685.2006.02.1.2
Timing Diagram
SQ
SQPULSE
Data
System Reset
System Start
CK
TSYNC TLAT
N=1 N=2 N=3
TOFF
TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA
TOFF > 2 PDATA
PDATA
Thermal Considerations
The AAT3685 is packaged in a Pb-free, 3x3mm
TDFN package which can provide up to 2.0W of
power dissipation when it is properly bonded to a
printed circuit board and has a maximum thermal
resistance of 50°C/W. Many considerations should
be taken into account when designing the printed
circuit board layout, as well as the placement of the
charger IC package in proximity to other heat gen-
erating devices in a given application design. The
ambient temperature around the charger IC will
also have an affect on the thermal limits of a bat-
tery 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:
Eq. 4:
Where:
PD= Total Power Dissipation by the Device
VIN = Input Voltage Level, VADP/USB
VBAT = Battery Voltage as Seen at the BAT Pin
ICC = Maximum Constant Fast Charge Current
Programmed for the Application
IOP = Quiescent Current Consumed by the
Charger IC for Normal Operation
Next, the maximum operating ambient temperature
for a given application can be estimated based on
the thermal resistance of the 3x3mm TDFN pack-
age when sufficiently mounted to a PCB layout and
the internal thermal loop temperature threshold.
Eq. 5:
TA = TJ - (θJA · PD)
PD = [(VIN - VBAT) · ICC + (VIN · IOP)]
Where:
TA= Ambient Temperature in Degrees C
TJ= Maximum Device Junction Temperature
Protected by the Thermal Limit Control
PD= Total Power Dissipation by the Device
θJA = Package Thermal Resistance in °C/W
Example:
For an application where the fast charge current is
set to 500mA, VUSB = 5.0V and the worst case bat-
tery voltage at 3.0V, what is the maximum ambient
temperature at which the thermal limiting will
become active?
Given:
VADP = 5.0V
VBAT = 3.0V
ICC = 500mA
IOP = 0.75mA
TJ= 140°C
θJA = 50°C/W
Using Equation 4, calculate the device power dissi-
pation for the stated condition:
Eq. 6:
The maximum ambient temperature before the
AAT3685 thermal limit protection will shut down
charging can now be calculated using Equation 5:
Eq. 7:
Therefore, under the stated conditions for this
worst case power dissipation example, the
AAT3685 will suspend charging operations when
the ambient operating temperature rises above
89.81°C.
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a
decoupling capacitor between the ADP/USB pin
and ground. 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 AAT3685 input is to be used in a system with
an external power supply source rather than a USB
port VBUS, 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 bounce effects when
the power supply is "hot plugged" in. Likewise, a
10µF or greater input capacitor is recommended
for the USB input to help buffer the effects of USB
source power switching noise and input cable
impedance.
Output Capacitor
The AAT3685 only requires a 1µF ceramic capaci-
tor on the BAT pin to maintain circuit stability. This
value should be increased to 10µF or more if the
battery connection is made any distance from the
charger output. If the AAT3685 is to be used in
applications where the battery can be removed
from the charger, such as in the case of 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 physi-
cally place the battery pack as close as possible
to the AAT3685 BAT pin. To minimize voltage
drops on the PCB, keep the high current carrying
traces adequately wide. For maximum power dis-
sipation of the AAT3685 3x3mm TDFN package,
the metal substrate should be solder bonded to
the board. It is also recommended to maximize
the substrate contact to the PCB ground plane
layer to further increase local heat dissipation.
Refer to the AAT3685 evaluation board for a good
layout example (see Figures 5 and 6).
TA = 140°C - (50°C/W · 1.00375W)
= 89.81°C
PD = (5.0V - 3.0V)(500mA) + (5.0V · 0.75mA)
= 1.00375W
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 19
AAT3685 Evaluation Board Layout
Figure 5: AAT3685 Evaluation Board Figure 6: AAT3685 Evaluation Board
Component Side Layout. Solder Side Layout.
AAT3685
Lithium-Ion/Polymer Battery Charger
20 3685.2006.02.1.2
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 21
AAT3685 Evaluation Board Schematic Diagram
GRN
LED D2
RED
LED D1
8.06K
R8
4.99K
R5
4.99K
R6 1K
R9
Open
R3
10K
R4 40.2K
R7
10µF
C1
1 2 3
PWRSEL
J2
SW1
LOHI
DAT
A
1 2 3
ON/OFF
J1
ADP/USB
1
BAT
2
GND
3
CHR
4
EN
5
TS
6
DATA 7
STAT2 8
STAT1 9
PWRSEL
10
SETL 11
SETH 12
AAT3685
U1
1
2
TB1
BAT
GND
TS
A
DP/USB
A
DP/USB
GND
TDFN33-12
1
2
3
4
5
Mini-B
10µF
C2
GND
ID
D+
D-
1
2
3
TB2
Open
R2
Open
R1
AAT3685
Lithium-Ion/Polymer Battery Charger
22 3685.2006.02.1.2
22 3685.2006.02.1.2
AAT3685 Evaluation Board Bill of Materials (BOM)
Quantity Description Desig. Footprint Manufacturer Part Number
1 Test Pin DATA PAD Mill-Max 6821-0-0001-00-00-08-0
1 Connecting Terminal Block, USB,GND TBLOK2 Phoenix Contact 277-1274-ND
2.54mm, 2 Pos
1 Connecting Terminal Block, BAT, GND, TS TBLOK3 Phoenix Contact 277-1273-ND
2.54mm, 3 Pos
1 USB 2.0 Receptacle, 5 Pos USB USB-MINI-B Hirose Electronic H2959CT-ND
Co. Ltd.
2 Capacitor, Ceramic, 10µF C1, C2 0805 MuRata 490-1717-1-ND
6.3V 10% X5R 0805
1 Typical Red LED, Super D1 1206LED Chicago Miniature CMD15-21SRC/TR8
Bright Lamp
1 Typical Green LED D2 1206LED Chicago Miniature CMD15-21VGC/TR8
Lamp
2 Header, 3-Pin J1, J2 HEADER2MM-3 Sullins 6821-0-0001-00-00-08-0
1 Resistor, 10kΩ1/16W 5% R4 0603 Panasonic/ECG P10KCFCT-ND
0603 SMD
2 Resistor, 4.99kΩ1/16W R5, R6 0603 Panasonic/ECG P4.99KHTR-ND
1% 0603 SMD
1 Resistor, 40.2kΩ1/16W R7 0603 Panasonic/ECG P40.2KHTR-ND
1% 0603 SMD
1 Resistor, 8.06kΩ1/16W R8 0603 Panasonic/ECG P8.06KHCT-ND
1% 0603 SMD
1 Resistor, 1kΩ1/16W 5% R9 0603 Panasonic/ECG P1.0KCGCT-ND
0603 SMD
1 Switch Tact 6mm SPST SW1 SWITCH ITT Industries/ CKN9012-ND
H = 5.0mm C&K Div.
1 AAT3685 Lithium-Ion/ U1 TDFN33-12 AnalogicTech AAT3685IWP
Polymer Battery Charger
Ordering Information
Package Information
All dimensions in millimeters.
Top View Bottom View
Detail "B"
Detail "A"
Side View
3.00 ± 0.05
Index Area
(D/2 x E/2)
Detail "A"
Detail "B"
1.70 ± 0.05
3.00 ± 0.05
0.05 ± 0.05
0.229 ± 0.051
7.5° ± 7.5°
2.40 ± 0.05
0.16
Pin 1 Indicator
(optional)
0.375 ± 0.125
0.3 ± 0.10
0.45 ± 0.050.23 ± 0.05
0.075 ± 0.075
0.1 REF
0.8 + 0.05
-0.20
Option A:
C0.30 (4x) max
Chamfered corner
Option B:
R0.30 (4x) max
Round corner
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.
Package Marking1Part Number (Tape and Reel)2
TDFN33-12 RNXYY AAT3685IWP-4.2-T1
AAT3685
Lithium-Ion/Polymer Battery Charger
3685.2006.02.1.2 23
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
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830 E. Arques Avenue, Sunnyvale, CA 94085
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.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold
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