General Description
The AAT3688 BatteryManagerTM is a member of
AnalogicTech's Total Power Management ICTM
(TPMICTM) product family. This device is a highly
integrated single cell lithium-ion/polymer battery
charger IC designed to operate with USB port
inputs. It requires the minimum number of external
components.
The AAT3688 precisely regulates battery charge
voltage and current for 4.2V lithium-ion/polymer bat-
tery cells. Depending on the USB port type, the
AAT3688 charge current can be programmed for
two separate levels up to 500mA. An optional
Charge Reduction Loop is built in to allow users to
charge the battery with available current from a USB
port, 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 AAT3688 is available in a Pb-free, thermally-
enhanced, space-saving 12-pin 3x3mm TDFN
package and is rated over the -40C to +85C tem-
perature range.
Features
USB Charger
-- Programmable up to 500mA 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 for USB Charging
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
BluetoothTM Headsets
Cellular Telephones
Digital Still Cameras
Hand-Held PCs
MP3 Players
Personal Data Assistants (PDAs)
Other Lithium-Ion/Polymer Battery-Powered
Devices
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
Typical Application
AAT3688
C2
10
F
BATT-
TEMP
USB Input
Battery Pack
Serial Data
USB
USBSEL
GND
TS
BAT
BATT+
USB Hi/Lo Select
STAT1
R
SETH
USBH
R
SETL
USBL
CHR
EN
STAT2
DATA
Enable
3688.2006.04.1.3
1
BatteryManager
TM
Pin Descriptions
Pin Configuration
TDFN33-12
(Top View)
USB
BAT
GND
1
CHR
EN
TS
USBH
USBL
USBSEL
STAT1
STAT2
DATA
2
3
4
5
6
12
11
10
9
8
7
Pin #
Name
Type
Function
1
USB
In
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 USB pin to
disable this function.
5
EN
In
Enable pin. Logic high enables the IC.
6
TS
In/Out
Connect to 10k
NTC 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
USBSEL
In
When USB is present, use this pin to toggle between USBH and USBL
charging levels.
11
USBL
In/Out
Connect resistor here to set charge current for low-current USB port.
12
USBH
In/Out
Connect resistor here to set charge current for high-current USB port.
EP
Exposed paddle (bottom); connect to GND directly beneath package.
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
2
3688.2006.04.1.3
Absolute Maximum Ratings
1
Thermal Information
2
Symbol
Description
Value
Units
JA
Maximum Thermal Resistance (3x3mm TDFN)
50
C/W
P
D
Maximum Power Dissipation
2.0
W
Symbol
Description
Value
Units
V
P
USB Input Voltage, <30ms, Duty Cycle <10%
-0.3 to 7.0
V
V
P
USB Input Voltage, Continuous
-0.3 to 6.0
V
V
N
BAT, USBSEL, USBH, USBL, STAT1, STAT2, DATA, TS, CHR, EN
-0.3 to V
VP
+ 0.3
V
T
J
Operating Junction Temperature Range
-40 to 150
C
T
LEAD
Maximum Soldering Temperature (at leads)
300
C
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
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 Characteristics
1
V
ADP
= 5V, T
A
= -25C to +85C, unless otherwise noted. Typical values are at T
A
= 25C.
Symbol
Description
Conditions
Min
Typ
Max Units
Operation
USB
Input Voltage Range
4.0
5.5
V
V
UVLO
Under-Voltage Lockout
Rising Edge
3.0
V
Under-Voltage Lockout Hysteresis
150
mV
I
OP
Operating Current
CC Charge Current = 500mA
0.75
1.5
mA
I
SLEEP
Sleep Mode Current
V
BAT
= 4.25V
0.3
1.0
A
I
Leakage
Reverse Leakage Current from
V
BAT
= 4V, USB Pin Open
1.0
A
BAT Pin
Voltage Regulation
V
BAT_EOC
1
End of Charge Voltage Accuracy
4.158
4.2
4.242
V
V
BAT
/V
BAT
EOC Voltage Tolerance
0.5
%
V
MIN
Preconditioning Voltage Threshold
2.8
3.0
3.15
V
V
RCH
Battery Recharge Voltage Threshold
V
BAT_EOC
- 0.1
V
V
USB_CHR
USB Charge Reduction Regulation
No Connection on CHR Pin
4.3
4.5
4.64
V
V
CHR
CHR Pin Voltage Accuracy
1.9
2.0
2.1
V
Current Regulation
I
CH
Charge Current
50
500
mA
I
CH
/I
CH
Charge Current Regulation
10
%
Tolerance
V
USBH
USBH Pin Voltage
CC Mode
2.0
V
V
USBL
USBL Pin Voltage
CC Mode
2.0
V
K
IUH
Current Set Factor: I
CHARGE
/I
USBH
2000
K
IUL
Current Set Factor: I
CHARGE
/I
USBL
2000
Charging Devices
R
DS(ON)U
USB Charging Transistor
V
IN
= 5.5V
0.4
0.5
0.65
On Resistance
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
4
3688.2006.04.1.3
1. The AAT3688 output charge voltage is specified over the 0 to 70C ambient temperature range; operation over the -25C to +85C
temperature range is guaranteed by design.
Electrical Characteristics
1
V
ADP
= 5V, T
A
= -25C to +85C, unless otherwise noted. Typical values are at T
A
= 25C.
Symbol
Description
Conditions
Min Typ
Max Units
Logic Control / Protection
V
USBSEL(H)
Input High Threshold
1.6
V
V
USBSEL(L)
Input Low Threshold
0.4
V
V
EN(H)
Input High Threshold
1.6
V
V
EN(L)
Input Low Threshold
0.4
V
V
STAT
Output Low Voltage
STAT Pin Sinks 4mA
0.4
V
I
STAT
STAT Pin Current Sink Capability
8.0
mA
V
OVP
Over-Voltage Protection Threshold
4.4
V
Pre-Charge Current I
TK
/I
CHG
For USBH Mode
10
%
For USBL Mode
50
Charge Termination Threshold Current
For USBH Mode
7.5
%
I
TERM
/I
CHG
Charge Termination Threshold Current
For USBL Mode
35
%
I
TERM
/I
CHG
I
TS
Current Source from TS Pin
70
80
90
A
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
V
DATA(H)
Input High Threshold
1.6
V
V
DATA)(L)
Input Low Threshold
0.4
V
SQ
PULSE
Status Request Pulse Width
Status Request
200
ns
t
PERIOD
System Clock Period
50
s
f
DATA
Data Output Frequency
20
kHz
T
OVSD
Over-Temperature Shutdown Threshold
145
C
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
5
1. The AAT3688 output charge voltage is specified over the 0 to 70C ambient temperature range; operation over the -25C to +85C
temperature range is guaranteed by design.
Typical Characteristics
Preconditioning Charge Current vs. Temperature
(USBH; USBH = 8.06k
)
Temperature (
C)
I
CH
(mA)
40
45
50
55
60
-50
-25
0
25
50
75
100
Preconditioning Threshold
Voltage vs. Temperature
Temperature (
C)
V
MIN
(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)
V
BAT
(V)
4.158
4.179
4.200
4.221
4.242
-50
-25
0
25
50
75
100
Recharge Voltage vs. Temperature
Temperature (
C)
V
RCH
(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)
V
BAT
(V)
4.158
4.179
4.200
4.221
4.242
4.5
4.75
5
5.25
5.5
I
FASTCHARGE
vs. R
SET
R
SET
(k
)
I
FASTCHARGE
(mA)
10
100
1000
1
10
100
1000
USBL
USBH
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
6
3688.2006.04.1.3
Typical Characteristics
Fast Charge Current vs. Supply Voltage
(USBH; USBH = 8.06k
)
Supply Voltage (V)
I
CH
(mA)
0
100
200
300
400
500
600
4.40
4.50
4.60
4.70
4.80
4.90
5.00
0
C
25
C
70
C
Fast Charge Current vs. Supply Voltage
(USBL; USBL = 40.2k
)
Supply Voltage (V)
I
CH
(mA)
0
20
40
60
80
100
120
4
4.5
5.5
6.5
5
6
V
BAT
= 3.3V
V
BAT
= 3.5V
V
BAT
= 3.9V
Fast Charge Current vs. Supply Voltage
(USBH; USBH = 8.06k
)
Supply Voltage (V)
I
CH
(mA)
0
100
200
300
400
500
600
4
4.25
4.5
4.75
5
5.25
5.5
5.75
6
V
BAT
= 3.5V
V
BAT
= 3.3V
V
BAT
= 3.9V
Charging Current vs. Battery Voltage
(USBL; USBL = 40.2k
)
Battery Voltage (V)
I
CH
(mA)
0
20
40
60
80
100
120
2.5
3
3.5
4
4.5
Charging Current vs. Battery Voltage
(USBH; USBH = 8.06k
)
Battery Voltage (V)
I
CH
(A)
0
100
200
300
400
500
600
2.5
3
3.5
4
4.5
Fast Charge Current vs. Temperature
(USBH; USBH = 8.06k
)
Temperature (
C)
I
CH
(mA)
440
450
460
470
480
490
500
510
520
530
540
-50
-25
0
25
50
75
100
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
7
Typical Characteristics
USB Charge Current vs. Time
(USBH; USBH = 8.06k
)
Time (sec)
USB V
BUS
(200mV/div)
USB Charge
Current
(200mA/div)
USB Peripheral
Current
Consumption
(200mA/div)
0
2
4
6
8
10
Charge Reduction
Mode Activated
USB Supply Current vs. USBH Resistor
USBH Resistor (k
)
I
Q
(mA)
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
1
10
100
1000
Constant Current
Pre-Conditioning
V
IL
vs. Supply Voltage
USBSEL (Falling)
Supply Voltage (V)
V
IL
(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
V
IH
vs. Supply Voltage
USBSEL (Rising)
Supply Voltage (V)
V
IH
(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
V
IL
vs. Supply Voltage
EN Pin (Falling)
Supply Voltage (V)
V
IL
(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
V
IH
vs. Supply Voltage
EN Pin (Rising)
Supply Voltage (V)
V
IH
(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
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
8
3688.2006.04.1.3
Typical Characteristics
Temperature Sense Output
Current vs. Temperature
Temperature (
C)
TS Pin CUrrent (
A)
72
74
76
78
80
82
84
86
88
-50
-25
0
25
50
75
100
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
9
Functional Block Diagram
Charge
Control
Current
Compare
Reverse Blocking
CV/
Precharge
USB
USBSEL
Constant
Current
BAT
UVLO
Over-
Temperature
Protect
Charge
Status
STAT2
STAT1
TS
Window
Comparator
80A
USBH
USBL
Serial
Data
DATA
GND
Charge
Reduction
Loop
CHR
EN
IC enable
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
10
3688.2006.04.1.3
Functional Description
The AAT3688 is a highly integrated single cell lithi-
um-ion/polymer battery charger IC designed to
operate from USB port V
BUS
supplies, while requir-
ing a minimum number of external components.
The device precisely regulates battery charge volt-
age and current for 4.2V lithium-ion/polymer bat-
tery cells.
The AAT3688 is specifically designed for being
powered from a USB port V
BUS
supply, but it can
also be powered from any input voltage source
capable supplying 4.5V to 5.5V for loads up to
500mA. Depending on the USB port type, the
AAT3688 constant charge current can be external-
ly programmed for two levels, USB high and USB
low, for maximum constant current charge levels
up to 500mA. Typically, the USB charge levels are
set at 500mA and 100mA for the USBH and USBL
modes; however, the user may program either
mode to any level they desire below 500mA. The
USBH/L mode has an automatic Charge Reduction
Loop control to allow users to charge the battery
with limited available current from a USB port while
maintaining the regulated port voltage. This sys-
tem assures the battery charge function will not
overload a USB 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 AAT3688 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 AAT3688 has four basic modes for the battery
charge cycle and is powered from the USB input:
pre-conditioning/trickle charge; constant current/fast
charge; constant voltage; and end of charge. For ref-
erence, Figure 1 shows the current versus voltage
profile during charging phases.
Battery Preconditioning
Before the start of charging, the AAT3688 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 (V
UVLO
), 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 AAT3688
checks the state of the battery. If the cell voltage is
below the Preconditioning Voltage Threshold (V
MIN
),
the AAT3688 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 (V
MIN
). At this point, the AAT3688
begins the constant current fast charging phase.
The fast charge constant current (I
CC
) amplitude is
determined by the selected charge mode USBH or
USBL and is programmed by the user via the R
SETH
and R
SETL
resistors. The AAT3688 remains in con-
stant current charge mode until the battery reaches
the voltage regulation point, V
BAT
.
Constant Voltage Charging
The system transitions to a constant voltage charg-
ing mode when the battery voltage reaches output
charge regulation threshold (V
BAT
) 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 (V
RCH
).
When the input supply is disconnected, the charg-
er will also automatically enter power-saving sleep
mode. Only consuming an ultra-low 0.3A in sleep
mode, the AAT3688 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 AAT3688 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.
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
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
Temp. 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
Yes
Yes
USB Detect
USBSEL > 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
USB High
Current Loop
USB Low
Current Loop
USB Low
Current Loop
No
Yes
No
Fault
Conditions Monitor
OV, OT
Yes
USB Voltage Test
V
USB
< 4.5V
USB Voltage
Regulation
Enable
USB Voltage
Regulation
Enable
USB Loop
Current
Reduction in USB
Charging Mode
USB Loop
Current
Reduction in USB
Charging Mode
No
USB Power
USB Power
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
12
3688.2006.04.1.3
Application Information
USB System Power Charging
The USB charge mode provides two programma-
ble fast charge levels up to 500mA for each, USB
high and USB low, USBH and USBL, respectively.
The USBH or USBL modes may be externally
selected by the USB select pin (USBSEL). When
the USBSEL pin is connected to a logic high level,
the USBH level will be active. Conversely, when
USBSEL is pulled to a logic low level (ground), the
USBL level will be used for fast charging. Typically
USBH is set for 500mA and USBL is set for 100mA.
However, these two USB charge levels may be
user programmed to any level between 50mA and
500mA by selecting the appropriate resistor values
for R
SETH
and R
SETL
. Refer to Table 1 for recom-
mended R
SETH
and R
SETL
values for the desired
USB input constant current charge levels.
USB Charge Reduction
In many instances, product system designers do
not know the real properties of a potential USB 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 USB port being used to sup-
ply the charger is unable to provide the pro-
grammed fast charge current, or if the system
under charge must also share supply current with
other functions, the AAT3688 will automatically
reduce USB fast charge current to maintain port
integrity and protect the host system.
The USB charge reduction system becomes active
when the voltage on the USB input falls below the
USB charge reduction threshold (V
USBCHR
), which
is typically 4.5V. Regardless of which USB charge
function is selected (USBH or USBL), the charge
reduction system will reduce the fast charge cur-
rent level in a linear fashion until the voltage
sensed on the USB input recovers above the
charge reduction threshold voltage. The USB
charge reduction threshold (V
USBCHR
) may be
externally set to a value lower than 4.5V by placing
a resistor divider network between V
USB
and
ground with the center connected to the CHR pin.
The USB charge reduction feature may be disabled
by connecting a 10k
resistor from the CHR pin
directly to the USB input pin.
The following equation may be used to approximate
a USB charge reduction threshold below 4.5V:
Eq. 1:
where R11/R12 << 1M
.
V
USBCHR
= 2.0V
R12
R12 + R11
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
13
Table 1: Recommended R
SET
Values.
Figure 2: Internal Equivalent
Circuit for the CHR Pin.
1.025M
825k
R11
R12
V
CHR
= 2.0V
V
USB
USB
CHR
USBH
USBL
I
CC
R
SET
(k
)
R
SET
(k
)
50
86.6
86.6
75
57.6
57.6
100
42.2
42.2
200
21.0
20.5
300
13.7
13.7
400
10.2
10.2
500
8.06
8.06
USB Input Charge Inhibit and Resume
The AAT3688 UVLO and power on reset feature
will function when the USB input pin voltage level
drops below the UVLO threshold. At this point, the
charger will suspend charging and shut down.
When power is re-applied to the 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.
Enable / Disable
The AAT3688 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 AAT3688 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
USB input is programmed with set resistors placed
between the USBH and USBL pins and ground. The
accuracy of the fast charge, as well as the precondi-
tioning trickle charge current, is dominated by the
tolerance of the set resistors used. For this reason,
1% tolerance metal film resistors are recommended
for programming the desired constant current level.
The USB input fast charge constant current charge
control provides for two current set levels, USBH
and USBL. The USBSEL pin is used to select the
high or low charge current levels in the USB charge
mode. When the USBSEL pin is pulled to a voltage
level above the V
USBSEL(H)
threshold, the USBH cur-
rent level will be selected. Conversely, this pin
should be pulled below the V
USBSEL(L)
to enable the
USBL charge level. Typically, the two R
SETH
and
R
SETL
for the USBH and USBL functions are fixed
for 500mA and 100mA USB fast charge levels.
However, these two charge levels may be set to any
level between 50mA and 500mA, depending upon
the system design requirements for a given USB
charge application. Refer to Table 1 and Figure 3
for recommended R
SETH
and R
SETL
values.
Figure 3: I
FASTCHARGE
vs. R
SET
.
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 (V
OVP
). If an
over-voltage condition occurs, the AAT3688 charge
control will shut down the device until voltage on
the BAT pin drops below the over-voltage protec-
tion threshold (V
OVP
). The AAT3688 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 AAT3688 has a thermal protection control cir-
cuit which will shut down charging functions should
the internal die temperature exceed the preset
thermal limit threshold.
R
SET
(k
)
I
FASTCHARGE
(mA)
10
100
1000
1
10
100
1000
USBL
USBH
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
14
3688.2006.04.1.3
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 AAT3688 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 10k
at room temperature (25C). The TS pin
has been specifically designed to source 80A 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 AAT3688 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 10k
resistor.
Battery Charge Status Indication
The AAT3688 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 AAT3688 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 AAT3688. 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.
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
15
Table 2: LED Display Status Conditions.
Event Description
STAT1
STAT2
Charge Disabled or Low Supply
Off
Off
Charge Enabled Without Battery
Flash
1
Flash
1
Battery Charging
On
Off
Charge Completed
Off
On
Fault
On
On
1. Flashing rate depends on output capacitance.
The LED anodes should be connected to V
USB
.
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 (V
F
) is typically
2.0V @ 2mA.
Table 2 shows the four status LED display conditions.
Digital Charge Status Reporting
The AAT3688 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 V
USB
. 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 1.5k
resis-
tor is recommended when pulling the DATA pin
high to 5.0V at the V
USB
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 - 2.0V)
R
B(STAT1)
=
= 1.5k
2mA
(V
USB
-
V
F(LED)
)
R
B(STAT1/2)
=
I
LED(STAT1/2)
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
16
3688.2006.04.1.3
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
17
Table 3: Serial Data Report Table.
Figure 4: Data Pin Application Circuit.
AAT3688
Status
Control
1.8V to 5.0V
DATA Pin
R
PULL_UP
P 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
USBH Battery Condition Mode
14
USBH Charge Reduction in Constant Current Mode
15
USBH Constant Current Mode
16
USBH Constant Voltage Mode
17
USBH End of Charging
18
USBL Battery Condition Mode
19
USBL Charge End of Charging Reduction in Constant Current Mode
20
USBL Constant Current Mode
21
USBL Constant Voltage Mode
22
USBL 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 T
LO(DATA)
. Upon sensing
the rising edge of the end of the data request pulse,
the AAT3688 status data control will reply the data
word back to the system microcontroller after a
delay specified by the data report time specification
T
DATA(RPT)
. The period of the following group of data
pulses will be specified by the T
DATA
specification.
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
18
3688.2006.04.1.3
Timing Diagram
SQ
SQ
PULSE
Data
System Reset
System Start
CK
T
SYNC
T
LAT
N=1
N=2
N=3
T
OFF
T
DATA(RPT)
= T
SYNC
+ T
LAT
< 2.5 P
DATA
T
OFF
> 2 P
DATA
P
DATA
Thermal Considerations
The AAT3688 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 50C/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:
P
D
= Total Power Dissipation by the Device
V
IN
= Input Voltage Level, V
USB
V
BAT
= Battery Voltage as Seen at the BAT Pin
I
CC
= Maximum Constant Fast Charge Current
Programmed for the Application
I
OP
= 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: T
A
= T
J
- (
JA
P
D
)
P
D
= [(V
IN
- V
BAT
)
I
CC
+ (V
IN
I
OP
)]
Where:
T
A
= Ambient Temperature in Degrees C
T
J
= Maximum Device Junction Temperature
Protected by the Thermal Limit Control
P
D
= Total Power Dissipation by the Device
JA
= Package Thermal Resistance in C/W
Example:
For an application where the fast charge current is
set to 500mA, V
USB
= 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:
V
ADP
= 5.0V
V
BAT
= 3.0V
I
CC
= 500mA
I
OP
= 0.75mA
T
J
= 140C
JA
= 50C/W
Using Equation 4, calculate the device power dissi-
pation for the stated condition:
Eq. 6:
The maximum ambient temperature before the
AAT3688 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
AAT3688 will suspend charging operations when
the ambient operating temperature rises above
89.81C.
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a
decoupling capacitor between the V
USB
pin and
ground. 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 AAT3688 USB input is to be used in a system
with an external power supply source rather than a
USB port V
BUS
, such as a typical AC-to-DC wall
adapter, then a C
IN
capacitor in the range of 10F
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 10F or greater input
capacitor is recommended for the USB input to
help buffer the effects of USB source power switch-
ing noise and input cable impedance.
Output Capacitor
The AAT3688 only requires a 1F ceramic capaci-
tor 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 AAT3688 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
10F 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 AAT3688 BAT pin. To minimize voltage
drops on the PCB, keep the high current carrying
traces adequately wide. For maximum power dis-
sipation of the AAT3688 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 AAT3688 evaluation board for a good
layout example (see Figures 5 and 6).
T
A
= 140
C - (50C/W 1.00375W)
= 89.81
C
P
D
= (5.0V - 3.0V)
(500mA) + (5.0V
0.75mA)
= 1.00375W
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
19
AAT3688 Evaluation Board Layout
Figure 5: AAT3688 Evaluation Board
Figure 6: AAT3688 Evaluation Board
Component Side Layout.
Solder Side Layout.
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
20
3688.2006.04.1.3
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
21
AAT3688 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
10F
C1
1 2 3
USBSEL
J2
SW1
LO
HI
DATA
1 2 3
ON/OFF
J1
USB
1
BAT
2
GND
3
CHR
4
EN
5
TS
6
DATA
7
STAT2
8
STAT1
9
USBSEL
10
USBL
11
USBH
12
AAT3688
U1
1
2
TB1
BAT
GND
TS
USB
GND
TDFN33-12
1
2
3
4
5
Mini-B
10F
C2
GND
ID
D+
D-
VBUS
1
2
3
TB2
Open
R2
Open
R1
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
22
3688.2006.04.1.3
22
3688.2006.04.1.3
AAT3688 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, 10F
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, 10k
1/16W 5%
R4
0603
Panasonic/ECG
P10KCFCT-ND
0603 SMD
2
Resistor, 4.99k
1/16W R5,
R6
0603
Panasonic/ECG
P4.99KHTR-ND
1% 0603 SMD
1
Resistor, 40.2k
1/16W
R7
0603
Panasonic/ECG
P40.2KHTR-ND
1% 0603 SMD
1
Resistor, 8.06k
1/16W R8
0603
Panasonic/ECG
P8.06KHCT-ND
1% 0603 SMD
1
Resistor, 1k
1/16W 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
AAT3688 USB Port Lithium-
U1
TDFN33-12
AnalogicTech
AAT3688IWP
Ion/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
0.05
0.23
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
Marking
1
Part Number (Tape and Reel)
2
TDFN33-12
PKXYY
AAT3688IWP-4.2-T1
AAT3688
USB Port Lithium-Ion/Polymer Battery Charger
3688.2006.04.1.3
23
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Advanced Analogic Technologies, Inc.
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 sub-
ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech's standard warranty. Testing and other quality con-
trol techniques are utilized to the extent AnalogicTech deems necessary to support this warranty. Specific testing of all parameters of each device is not necessarily performed.
AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are regis-
tered trademarks or trademarks of their respective holders.
PDF 
ZIP