AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
1
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
General Description
The AAT3682 is a lithium-ion/polymer linear battery
charger. It is designed for compact portable applications
with a single-cell battery. The AAT3682 precisely regu-
lates battery charge voltage and charge current, and
offers an integrated pass device, minimizing the number
of external components required.
The AAT3682 charges the battery in three different
phases: preconditioning, constant current, and constant
voltage. In preconditioning mode, the charge current has
two different levels and is controlled by one external pin.
Battery charge temperature and charge state are care-
fully monitored for fault conditions. A battery charge
stable monitor output pin is provided to indicate the bat-
tery charge status through a display LED or interface to
a system controller. The AAT3682 has a sleep mode
option for when the input supply is removed. In this
mode, it draws only 2.0μA of typical current.
The AAT3682 is available in a Pb-free, 16-pin QFN44
package and is specified over the -20°C to +70°C tem-
perature range.
Features
• VIN Range: 4.7V to 6.0V
• Low Quiescent Current, Typically 0.5mA
• 1% Accurate Preset Voltage
• Up to 1A of Charging Current
• Integrated Pass Device
• Battery Temperature Monitoring
• Fast Trickle Charge Option
• Deep Discharge Cell Conditioning
• LED Charge Status Output or System Microcontroller
Serial Interface
• Power-On Reset
• Lower Power Sleep Mode
• Status Outputs for LED or System Interface Indicates
Charge and Fault Conditions
• Temperature Range: -20°C to +70°C
• 16-Pin QFN44 Package
Applications
• Cellular Telephones
• Digital Still Cameras
• Hand-Held PCs
• MP3 Players
• Personal Data Assistants (PDAs)
Typical Application
VP
Gate
DRV
CSI
VCC
VSS
BAT
T2X
BSENSE
TS
STAT
RSENSE
CIN = 10μF
COUT= 1μF
LED 1
R2= 1K
BATT+
BATT-
RT1
VP
RT2
TEMP
A
dapter
R4
R3
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
2Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Pin Descriptions
Pin # Symbol Function
1 TS Battery temperature sense input.
2, 3, 8, 12 N/C Not connected.
4 STAT
Battery charger status output. Connect an LED in series with 2.2k from STAT to VIN for a visual
monitor battery charge state or connect to a microcontroller to monitor battery status. A 100k
resistor should be placed between STAT and VIN for this function.
5 VSS Common ground connection.
6 DRV Battery charge control output.
7 T2X
Battery trickle charge control input. Connect this pin to VSS to double the battery trickle charge cur-
rent. Leave this pin fl oating for normal trickle current (10% of full charge current). To enter micro-
controller fast-read status, pull this pin high during power up.
9BAT
Battery charge control output. Current regulated output to charge the battery. For best operation, a
0.1μF ceramic capacitor should be placed between BAT and GND.
10 VSS Common ground connection.
11 GATE Input voltage for biasing the pass device.
13 VP Battery charge power input.
14 CSI Current sense input.
15 BSENSE Battery voltage sense input.
16 VCC AAT3682 bias input power.
EP Exposed paddle (bottom); connect to GND directly beneath the package.
Pin Configuration
QFN44-16
(Top View)
1
2
3
4
12
11
10
9
5
6
7
8
16
15
14
13
TS
N/C
N/C
STAT
VSS
DR
V
T2X
N/C
BAT
VSS
GATE
N/C
AAT3682
VP
CSI
BSENSE
VCC
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
3
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
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.
3. Derate 20mW/°C above 25°C.
Absolute Maximum Ratings1
Symbol Description Value Units
VIN VIN Relative to GND -0.3 to 6.0
V
VCSI CSI to GND -0.3 to VCC + 0.3
VT2X T2X to GND -0.3 to 5.5
Bias, VBAT BAT to GND -0.3 to VCC + 0.3
TJOperating Junction Temperature Range -40 to 85 °C
Thermal Information
Symbol Description Value Units
JA Maximum Thermal Resistance2, 3 50 °C/W
PDPower Dissipation (TA = 25°C) 2.0 W
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
4Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
1. The AAT3682 output charge voltage is specified over the 0°C to 55°C ambient temperature range; operation over -20°C to 70°C is guaranteed by design.
2. 1A of charging current is only for dynamic applications and not DC. In addition, the ambient temperature must be at or below 50°C.
Electrical Characteristics1
VIN = 5.0V, TA = -20°C to +70°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol Description Conditions Min Typ Max Units
VIN Operation Input Voltage 4.7 6.0 V
ICC Operating Current VIN = 5.5V, VCH = 4.2 0.5 3.0 mA
ISLEEP Sleep Mode Current VIN = 3.5V, VCH = 4.2 3.0 6.0 μA
ISTAT(HI) STAT High Level Output Leakage Current VIN = 5.5V -1.0 +1.0 μA
VSTAT(LOW) STAT Low Level Sink Current VIN = 5.5V, ISINK = 5mA 0.3 0.6 V
VCH Output Charge Voltage Regulation VBAT = 4.2V TA = 25°C 4.175 4.20 4.225 V
See Note 1 4.158 4.20 4.242
VCS Charge Current Regulation VIN = 5.5V, VCH = 4.2 90 100 110 mV
ICH Charge Current2VIN = 5.5V 1.0 A
VMIN Preconditioning Voltage Threshold VCH = 4.2V 3.04 3.1 3.16 V
VTRICKLE Trickle Charge Current Regulation T2X Floating; VCH = 4.2V 10 mV
T2X Trickle Charge Current Gain T2X = VSS 1.8
VTS1 Low Temperature Threshold 29.1 30 30.9 %VCC
VTS2 High Temperature Threshold 58.2 60 61.8 %VCC
VTERM Charge Termination Threshold Voltage 4 12 24 mV
VRCH Battery Recharge Voltage Threshold VCH = 4.2V 4.018 4.1 4.182 V
VUVLO Under-Voltage Lockout VIN Rising, TA = 25°C 3.5 4.0 4.5 V
VOVP Over-Voltage Protection Threshold 4.4 V
VOCP Over-Current Protection Threshold 200 %VCS
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
5
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Typical Characteristics
Battery Recharge Threshold Voltage
vs.Temperature
(RSENSE = 0.15Ω
)
Temperature (°C)
Battery Recharge
Threshold Voltage (V)
3.80
3.85
3.90
3.95
4.00
4.05
4.10
4.15
4.20
-50 -25 0 25 50 75 100
Regulated Output Voltage vs. Charge Current
(RSENSE = 0.15Ω)
)
Charging Current (mA)
Regulated Output Voltage (V)
4.15
4.17
4.19
4.21
4.23
4.25
0 100 200 300 400 500 600 700
Regulated Output Voltage vs. Input Voltage
(RSENSE = 0.15Ω)
Input Voltage
(V)
Regulated Output Voltage
(V)
4.00
4.10
4.20
4.30
4.40
4.0 4.5 5.0 5.5 6.0 6.5
Regulated Output Voltage vs. Temperature
(RSENSE = 0.15Ω)
Temperature (°C)
Regulated Output Voltage (V)
4.100
4.125
4.150
4.175
4.200
4.225
4.250
-50 -25 0 25 50 75 100
Trickle Charge Threshold Voltage
vs.Temperature
(RSENSE = 0.15Ω)
Temperature (°C)
Trickle Charge Threshold Voltage
(V)
2.8
2.9
3.0
3.1
3.2
3.3
3.4
-50 -25 0 25 50 75 100
Trickle Charge Current vs. Temperature
(RSENSE = 0.15Ω)
Temperature (°C)
Trickle Charge Current
(mA)
130
135
140
145
150
155
160
165
170
-50 -25 0 25 50 75 100
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
6Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Typical Characteristics
Charging Current vs. Temperature
(RSENSE = 0.15Ω)
Temperature (°C)
Charging Current
(mA)
650
660
670
680
690
700
-50 -25 0 25 50 75 100
Charging Current vs. Input Voltage
(RSENSE = 0.15Ω with External Schottky)
Input Voltage (V)
Charging Current
(mA)
0
100
200
300
400
500
600
700
4.0 4.5 5.0 5.5 6.0
VBAT = 4.1V
VBAT = 3.6V
Charging Current vs. Battery Voltage
(RSENSE = 0.15Ω with External Schottky)
Battery Voltage (V)
Charging Current
(mA)
0
100
200
300
400
500
600
700
2.5 3.0 3.5 4.0 4.5 5.0
VIN = 4.5V
VIN = 4.75V
VIN = 5.5V
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.15Ω; 1.8X Mode)
Input Voltage (V)
Trickle Charge Current
(mA)
130
135
140
145
150
155
160
165
170
4.0 4.5 5.0 5.5 6.0
Charging Current vs. Input Voltage
(RSENSE = 0.2Ω with External Schottky)
Input Voltage (V)
Charging Current
(mA)
0
100
200
300
400
500
600
4.0 4.5 5.0 5.5 6.0
VBAT = 4.0V
VBAT = 3.6V
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.2Ω; 1.8X Mode)
Input Voltage (V)
Trickle Charge Current
(mA)
94
96
98
100
102
104
4 4.5 5 5.5 6
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
7
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Typical Characteristics
Charging Current vs. Battery Voltage
(RSENSE = 0.2Ω with External Schottky)
Battery Voltage (V)
Charging Current
(mA)
0
100
200
300
400
500
600
2.5 3.0 3.5 4.0 4.5 5.0
VIN = 4.5V
VIN = 4.75V
VIN = 5.5V
Safe Operating Area
(TJ(MAX) = 120°C)
Charging Current (A)
Maximum Input Voltage (V)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
0.0 0.2 0.4 0.6 0.8
TAMB = 85°C
Schottky VF = 0.2V
TAMB = 70°C
TAMB = 50°C TAMB = 40°C
Safe Operating Area
(TJ(MAX) = 150°C)
Charging Current (A)
Maximum Input Voltage (V)
5.0
5.2
5.4
5.6
5.8
6.0
6.2
0 0.2 0.4 0.6 0.8
TAMB = 85°C
TAMB = 70°C
TAMB = <50°C
Schottky VF = 0.2V
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
8Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Functional Description
The AAT3682 is a linear charger designed for single-cell
lithium-ion/polymer batteries. It is a full-featured bat-
tery management system IC with multiple levels of
power savings, system communication, and protection
integrated inside. Refer to the block diagram above and
the flow chart and typical charge profile graph (Figures
1 and 2) in this section.
Cell Preconditioning
Before the start of charging, the AAT3682 checks sev-
eral conditions in order to maintain 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. Also, the cell
temperature, as reported by a thermistor connected to
the TS pin, must be within the proper window for safe
charging.
Functional Block Diagram
MUX
T2X
LED Signal
Generator
Microcontroller
Status Generator
Microcontroller
Read Enable
Charge Status
Logic Control
Power-On
Reset
VSS
STAT
DRV
GATE
BAT
Under-Voltage
Lock Out
Over-Current /
Short-Circuit
Protection
2X Trickle
Charge
Control
Loop Select
MUX
Driver
VREF
Temperature
Sense
Comparator
Voltage
Comparator
Voltage Loop
Error Amp
Current Loop
Error Amp
VP
VCC
BSENSE
T2X
TS
CSI
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
9
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
UVLO
Temperature Test
TS > VTS1
TS < VTS2
Power On Reset
Power On Reset
Preconditioning Test
Current Phase Test
VCH >VBAT
VMIN >VBAT
VTERM
RSENSE
<VRCH
Voltage
Phase Test
VCC> VUVLO Shut Down
Mode
Shut Down
Mode
Yes
No
Yes
Yes Low Current
Conditioning
Charge
Low Current
Conditioning
Charge
(Trickle Charge)
Temperature
Fault
Temperature
Fault No
No
Current
Charging
Mode
Current
Charging
Mode
Yes
Voltage
Charging
Mode
Voltage
Charging
Mode
< IBAT
No
Yes
No
Charge Complete
Latch Off
Charge Complete
Latch Off
Figure 1: AAT3682 Operational Flow Chart.
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
10 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Preconditioning
(Trickle Charge)
Phase Constant Current
Phase Constant Voltage
Phase
Output Charge
Voltage (VCH)
Preconditioning
Voltage Threshold
(VMIN)
Regulation
Current
(ICHARGE(REG))
Trickle Charge
and Termination
Threshold
Figure 2: Typical Charge Profile.
When these conditions have been met and a battery is
connected to the BAT pin, the AAT3682 checks the state
of the battery. If the cell voltage is below VMIN, the
AAT3682 begins preconditioning the cell. This is per-
formed by charging the cell with 10% of the programmed
constant current amount. For example, if the programmed
charge current is 500mA, then the preconditioning mode
(trickle charge) current will be 50mA. Cell preconditioning
is a safety precaution for deeply discharged cells and,
furthermore, limits power dissipation in the pass transis-
tor when the voltage across the device is largest. The
AAT3682 features an optional T2X mode, which allows
faster trickle charging at approximately two times the
default rate. This mode is selected by connecting the T2X
pin to VSS. If an over-temperature fault is triggered, the
fast trickle charge will be latched off, and the AAT3682 will
continue at the default 10% charge current.
Constant Current Charging
The cell preconditioning continues until the voltage on
the BAT pin reaches VMIN. At this point, the AAT3682
begins constant current charging (fast charging). Current
level for this mode is programmed using a current sense
resistor RSENSE between the VCC and CSI pins. The CSI
pin monitors the voltage across RSENSE to provide feed-
back for the current control loop. The AAT3682 remains
in constant current charge mode until the battery reach-
es the voltage regulation point, VCH.
Constant Voltage Charging
When the battery voltage reaches VCH during constant
current mode, the AAT3682 transitions to constant volt-
age mode. The regulation voltage is factory programmed
to 4.2V. In constant voltage operation, the AAT3682
monitors the cell voltage and terminates the charging
cycle when the voltage across RSENSE decreases to
approximately 10mV.
Charge Cycle Termination,
Recharge Sequence
After the charge cycle is complete, the AAT3682 shuts
off the pass device and automatically enters power-
saving sleep mode. Either of two possible conditions will
bring the IC out of sleep mode: the battery voltage at
the BAT pin drops below VRCH (recharge threshold volt-
age) or the AAT3682 is reset by cycling the input supply
through the power-on sequence. Falling below VRCH sig-
nals the IC that it is time to initiate a new charge cycle.
Sleep Mode
When the input supply is disconnected, the device auto-
matically enters power-saving sleep mode. Only con-
suming an ultra-low 2μA current, the AAT3682 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 AAT3682 input
voltage drops, the device will enter the sleep mode and
automatically resume charging once the input supply has
recovered from its fault condition. This makes the
AAT3682 well suited for USB battery charger applica-
tions.
Charge Inhibit
The AAT3682 charging cycle is fully automatic; however,
it is possible to stop the device from charging even when
all conditions are met for proper charging. Switching the
TS pin to either VIN or GND will force the AAT3682 to turn
off the pass device and wait for a voltage between the
low and high temperature voltage thresholds.
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
11
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Sleep / Charge Complete
Temp., OC, OV Fault
Battery Conditioning
Constant Current Mode
Constant Voltage Mode
off / off / off / off
on / on / off / off
on / on / on / on
on / off / off / off
on / on / on / off
Charge Status Output Status LED Display
on/off
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
on/off on/off on/off
Figure 3: LED Display Output.
Resuming Charge and the VRCH Threshold
The AAT3682 will automatically resume charging under
most conditions when a battery charge cycle is inter-
rupted. Events such as an input supply interruption or
under voltage, removal and replacement of the battery
under charge, or charging a partially drained battery are
all possible. The AAT3682 will monitor the battery volt-
age and automatically resume charging in the appropri-
ate mode based upon the measured battery cell voltage.
This feature is useful for systems with an unstable input
supply, which could be the case when powering a char-
ger from a USB bus supply. It is also beneficial for charg-
ing or “topping off” partially discharged batteries. The
only restriction on resuming charge of a battery is that
the battery cell voltage must be below the battery
recharge voltage threshold (VRCH) specification. There is
VRCH threshold hysteresis built into the charge control
system. This is done to prevent the charger from errone-
ously turning on and off once a battery charge cycle is
complete.
For example, the AAT3682 has a typical VRCH threshold of
4.1V. A battery under charge is above 4.1V, but is still in
the constant voltage mode because it has not yet
reached 4.2V to complete the charge cycle. If the battery
is removed and then placed back on the charger, the
charge cycle will not resume until the battery voltage
drops below the VRCH threshold. In another case, a bat-
tery under charge is in the constant current mode and
the cell voltage is 3.7V when the input supply is inadver-
tently removed and then restored. The battery is below
the VRCH threshold and the charge cycle will immediately
resume where it left off.
LED Display Charge Status Output
The AAT3682 provides a battery charge status output via
the STAT pin. STAT is an open-drain serial data output
capable of displaying five distinct status functions with
one LED connected between the STAT pin and VP. There
are four periods which determine a status word. Under
default conditions, each output period is one second
long; thus one status word will take four seconds to dis-
play through an LED. The five modes include:
1. Sleep/Charge Complete: The IC goes into Sleep
mode when no battery is present -OR- when the
charge cycle is complete.
2. Fault: When an over-current (OC) condition is
detected by the current sense and control circuit
-OR- when an over-voltage (OV) condition is detect-
ed at the BAT pin -OR- when a battery over-temper-
ature fault is detected on the TEMP pin.
3. Battery Conditioning: When the charge system is in
1X or 2X trickle charge mode.
4. Constant Current (CC) Mode: When the system is in
constant current charge mode.
5. Constant Voltage (CV) Mode: When the system is in
constant voltage charge mode.
An additional feature of the LED status display is for a
Battery Not Detected state. When the AAT3682 senses
there is no battery connected to the BAT pin, the STAT
output will turn the LED on and off at a rate dependent
on the size of the output capacitor being used. The LED
cycles on for two periods then remains off for two peri-
ods. See Figure 3 below.
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
12 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Sleep / Charge Complete
Temp., OC, OV Fault
Battery Conditioning
Constant Current Mode
Constant Voltage Mode
HI / HI / HI / HI
LO / LO / HI / HI
LO / LO / LO / LO
LO / HI / HI / HI
LO / LO / LO / HI
Charge Status Output Status STAT Level
Figure 4: Microcontroller Interface Logic Output.
High-Speed Data Reporting
An optional system microcontroller interface can be
enabled by pulling the T2X pin up to 4.5V to 5.5V during
the power-up sequence. The T2X pin should be pulled
high with the use of a 100k resistor. If the input supply
to VIN will not exceed 5.5V, then the T2X pin may be tied
directly to VIN through a 100k resistor. Since this is a
TTL level circuit, it may not be pulled higher than 5.5V
without risk of damage to the device.
When the high-speed data report feature is enabled, the
STAT output periods are sped up to 40μs, making the
total status word 160μs in length. See Figure 4 below.
An additional feature is the Output Status for the Battery
Not Detected state. When the AAT3682 senses there is
no battery connected to the BAT pin, the STAT pin cycles
for two periods, then remains off for two periods. When
in high-speed data reporting, the AAT3682 will only
trickle charge at the 2X trickle charge level. This is
because the T2X pin is pulled high to enable the high-
speed data reporting. A status display LED may not be
connected to the STAT pin when the high-speed data
reporting is being utilized. If both display modes are
required, the display LED must be switched out of the
circuit before the T2X pin is pulled high. Failing to do so
could cause problems with the high-speed switching con-
trol circuits internal to the AAT3682.
Charge Complete LED Status Mode
A simplified LED status can be obtained by configuring
the AAT3682 for high-speed data reporting mode (T2X
tied to VCC) and installing a 0.047μF capacitor from the
STAT pin to the VSS pin (see Figure 5). In this configura-
tion, the LED will be illuminated for all modes except the
Sleep/Charge Complete mode. In addition, the T2X input
must be tied to VCC through a 100k resistor. In this
mode, the trickle charge current will be 1.8X the normal
trickle charge level. To reset the trickle charge current to
the 1X level, the TS input must be temporarily toggled
low. Removing C3 forces the LED status to gradually dim
as the battery becomes fully charged (see Figure 5).
Protection Circuitry
The AAT3682 is a highly integrated battery management
system IC including several protection features. In addi-
tion to battery temperature monitoring, the IC constant-
ly monitors for over-current and over-voltage conditions;
if an over-current situation occurs, the AAT3682 latches
off the pass device to prevent damage to the battery or
the system, and enters shutdown mode until the over-
current event is terminated. An over-voltage condition is
defined as a condition where the voltage on the BAT pin
exceeds the maximum battery charge voltage. If an over-
voltage condition occurs, the IC turns off the pass device
until voltage on the BAT pin drops below the maximum
battery charge constant voltage threshold. The AAT3682
will resume normal operation after the over-current or
over-voltage condition is removed. During an over-cur-
rent or over-voltage event, the STAT will report a FAULT
signal. In the event of a battery over-temperature condi-
tion, the IC will turn off the pass device and report a
FAULT signal on the STAT pin. After the system recovers
from a temperature fault, the IC will resume operation in
the 1X trickle charge mode to prevent damage to the
system in the event a defective battery is placed under
charge. Once the battery voltage rises above the trickle
charge to constant current charge threshold, the IC will
resume the constant current mode.
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
13
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201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
1
2
J1
1
2
3
J2
1K
R4
0.2Ω
R2
1K
R3
2.2K
R1
100K
R6
100K
R5
D2
22μF
C1
10μF
C2
Green LED
VIN
GND
D1
47nF
C3
TS
1
N/C
2
N/C
3
STAT
4
VSS 5
DRV 6
T2X 7
N/C 8
BAT 9
VSS 10
GATE 11
N/C 12
VP
13 CSI
14 BSENSE
15 VCC
16
AAT3682
U1
100K
R7
2
1
3
SW-T2X
S1
1000pF
C4
4.7μF
C5
Remove capacitor for
progressive dimming
Figure 5: Evaluation Board Schematic.
Applications Information
Choosing a Sense Resistor
The charging rate recommended by lithium-ion/polymer
cell vendors is normally 1C, with a 2C absolute maximum
rating. Charging at the highest recommended rate offers
the advantage of shortened charging time without
decreasing the battery’s lifespan. This means that the
suggested fast charge rate for a 500mAH battery pack is
500mA. Refer to the Safe Operating Area curves in the
Typical Characteristics section of this datasheet to deter-
mine the maximum allowable charge current for a given
input voltage. The current sense resistor, RSENSE, programs
the charge current according to the following equation:
V
CC
- V
CSI
R
SENSE
=
I
CHARGE
Where ICHARGE is the desired typical charge current during
constant current charge mode. VCC - VCSI is the voltage
across RSENSE, shown in the Electrical Characteristics
table as VCS. To program a nominal 500mA charge cur-
rent during fast charge, a 200m value resistor should
be selected. Calculate the worst case power dissipated in
the sense resistor according to the following equation:
V
CS2
0.1V2
P = = = 50mW
R
SENSE 0.2Ω
A 500mW LRC type sense resistor from IRC is adequate
for this purpose. Higher value sense resistors can be
used, decreasing the power dissipated in the sense resis-
tor and pass transistor. The drawback of higher value
sense resistors is that the charge cycle time is increased,
so tradeoffs should be considered when optimizing the
design.
Thermistor
The AAT3682 checks battery temperature before starting
the charge cycle, as well as during all stages of charging.
This is accomplished by monitoring the voltage at the TS
pin. Either a negative temperature coefficient thermistor
(NTC) or positive-temperature coefficient thermistor
(PTC) can be used because the AAT3682 checks to see
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
14 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
that the voltage at TS is within a voltage window bound-
ed by VTS1 and VTS2. Please see the following equations
for specifying resistors:
RT1 and RT2 for use with NTC Thermistor:
RT1 =
5 ∙ RTH ∙ RTC
3 · (RTC - RTH)
RT2 =
5 ∙ RTH ∙ RTC
(2 ∙ RTC) - (7 ∙ RTH)
RT1 and RT2 for use with PTC Thermistor:
RT1 =
5 ∙ RTH ∙ RTC
3 · (RTH - RTC)
RT2 =
5 ∙ RTH ∙ RTC
(2 ∙ RTH) - (7 ∙ RTC)
Where RTC is the thermistor’s cold temperature resis-
tance and RTH is the thermistor’s hot temperature resis-
tance. See thermistor specifications for additional infor-
mation. To ensure there is no dependence on the input
supply changes, connect divider between VCC and VSS.
Disabling the temperature-monitoring function is
achieved by applying a voltage between VTS1 and VTS2 on
the TS pin.
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a decou-
pling capacitor between the VCC and VSS pins. An input
capacitor in the range of 1μF to 10μF 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. If the
AAT3682 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 bounce effects when the
power supply is “hot plugged” in.
Output Capacitor
The AAT3682 does not need an output capacitor for sta-
bility of the device itself. However, a capacitor connected
between BAT and VSS will control the output voltage
when the AAT3682 is powered up when no battery is
connected. The AAT3682 can become unstable if a high
impedance load is placed across the BAT pin to VSS.
Such a case is possible with aging li-ion/poly battery
cells. As cells age through repeated charge and dis-
charge cycles, the internal impedance can rise over time.
A 10μF or larger output capacitor will compensate for the
adverse effects of a high impedance load and assure
device stability over all operating conditions.
Power Dissipation
The voltage drop across the VP and BAT pins multiplied
times the charge current is used to determine the inter-
nal power dissipation. The maximum power dissipation
occurs when the input voltage is at a maximum and the
battery voltage is at the minimum preconditioning volt-
age threshold. This power is then multiplied times the
package theta to determine the maximum junction tem-
perature. The worst case power junction temperature is
calculated as follows:
P
MAX
= (V
IN(MAX)
- V
SENSE
- V
SCHOTTKY
- V
BAT(MIN)
) ⋅ I
CHG(MAX)
= (5.5V - 0.1V - 0.2V - 3.04V) ⋅ 550mA
= 1.2W
This equation can be used to determine the maximum
input voltage given the maximum junction and ambient
temperature and desired charge current.
T
J(MAX)
- T
AMB
V
IN(MAX)
= + V
BAT
+ V
SCHOTTKY
+ V
CS
= + 3.1V + 0.2V + 0.1V
= 5.3V
θ ⋅ I
CHG(MAX)
120°C - 70°C
50°C/W ⋅ 500mA
Operation Under No-Load
Under no-load conditions (i.e., when the AAT3682 is
powered with no battery connected between the BAT pin
and VSS), the output capacitor is charged up very quick-
ly by the trickle charge control circuit to the BAT pin until
the output reaches the recharge threshold (VRCH). At this
point, the AAT3682 will drop into sleep mode. The output
capacitor will discharge slowly by the capacitor’s own
internal leakage until the voltage seen at the BAT pin
drops below the VRCH threshold. This 100mV cycle will
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
15
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201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
continue at approximately 3Hz with a 0.1μF capacitor
connected. A larger capacitor value will produce a slower
voltage cycle. This operation mode can be observed by
viewing the STAT LED blinking on and off at the rate
established by the COUT value. For desktop charger appli-
cations, where it might not be desirable to have a “char-
ger ready” blinking LED, a large COUT capacitor in the
range of 100μF or more would prevent the operation of
this mode.
The AAT3682 features a charge status output. Connecting
a LED to the STAT pin will display all the three conditions
of battery operation. Once the adapter is connected to
the battery charger, the LED will be fully illuminated. As
the battery charges, the LED will gradually dim as it
transitions to constant current mode and to constant
voltage mode. Table 1 summarizes the conditions.
Charge Status LED Display
No Battery Connected Blinking
Battery Condition 100% LED Light
Constant Current 75% LED Light
Constant Voltage 25% LED Light
Sleep/Charge Complete Off
Table 1: Charging Status.
For applications where gradual dimming of the LED is not
desired, adding C3 (refer to Figure 5) between the STAT
pin and VSS will alter the charging status. In addition,
the AAT3682 must be configured to operate in the high
frequency STAT mode by connecting the T2X pin to VCC
via 100k resistor.
As the battery is transitioning from trickle charge to con-
stant current charge and constant voltage, the LED will
remain illuminated. Once the battery is fully charged,
the LED will shut off, indicating completion of charge.
Table 2 summarizes the conditions.
Charge Status LED Display
No Battery Connected Blinking
Battery Condition On
Constant Current On
Constant Voltage On
Sleep/Charge Complete Off
Table 2: Charging Status With C3 Connected.
Reverse Current Blocking Diode
A reverse blocking diode is generally required for the
circuit shown in Figure 5. The blocking diode gives the
system protection from a shorted input. If there is no
other protection in the system, a shorted input could
discharge the battery through the body diode of the
internal pass MOSFET. If a reverse blocking diode is
added to the system, a device should be chosen that can
withstand the maximum constant current charge current
at the maximum system ambient temperature.
Additionally, the blocking diode will prevent the battery
from being discharged to the UVLO level by the AAT3682
in the event that power is removed from the input to the
AAT3682. For this reason, the blocking diode must be
placed in the location shown in Figure 5.
Diode Selection
Typically, a Schottky diode is used in reverse current
blocking applications with the AAT3682. Other lower cost
rectifier type diodes may also be used if sufficient input
power supply headroom is available.
The blocking diode selection should based on merits of
the device forward voltage (VF), current rating, input
supply level versus the maximum battery charge volt-
age, and cost.
First, one must determine the appropriate minimum
diode forward voltage drop:
VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE)
Where:
VIN(MIN) = Minimum input supply level
VBAT(MAX) = Maximum battery charge voltage required
VF(TRAN) = Pass transistor forward voltage drop
VF(DIODE) = Blocking diode forward voltage
Based on the maximum constant current charge level set
for the system, the next step is to determine the mini-
mum current rating and power handling capacity for the
blocking diode. The constant current charge level itself
will dictate what the minimum current rating must be for
a given blocking diode. The minimum power handling
capacity must be calculated based on the constant cur-
rent amplitude and the diode forward voltage (VF):
V
F
P
D(MIN)
= I
CC
Where:
PD(MIN) = Minimum power rating for a diode selection
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
16 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Figure 6: Evaluation Board Top Side Layout. Figure 7: Evaluation Board Bottom Side Layout.
VF = Diode forward voltage
ICC = Constant current charge level for the system
Schottky Diodes
Schottky diodes are selected for this application because
they have a low forward voltage drop, typically between
0.3V and 0.4V. A lower VF permits a lower voltage drop
at the constant current charge level set by the system;
less power will be dissipated in this element of the cir-
cuit. A Schottky diode allows for lower power dissipation,
smaller component package sizes, and greater circuit
layout densities.
Rectifier Diodes
Any general purpose rectifier diode can be used with the
AAT3682 application circuit in place of a higher cost
Schottky diode. The design trade-off is that a rectifier
diode has a high forward voltage drop. VF for a typical
silicon rectifier diode is in the range of 0.7V. A higher VF
will place an input supply voltage requirement for the
battery charger system. This will also require a higher
power rated diode since the voltage drop at the constant
current charge amplitude will be greater. Refer to the
previously stated equations to calculate the minimum VIN
and diode PD for a given application.
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
17
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 25, 2012
Reference
Symbol Description Footprint Part Number Manufacturer
U1 Battery Charger AAT3682 QFN44-16 AAT3682-4.2 Skyworks
C1 Ceramic Capacitor 20μF-10V-X5R 1210 GRM32ER61A226KA65L Murata
C2 Ceramic Capacitor 10μF-10V-X5R 0805 GRM21BR61A106KE19L
C3 Ceramic Capacitor 0.047μF-10V-X7R 0805 VJ0805Y473KXQA Vishay
R1 Resistor 2.2k 1/4W 0402 CRCW04022211F
R2 Current Sensing Resistor 0.2 1/4W 0805 RL1220S-R20-F SSM Susumu
R3 Resistor 1.0k 1% 1/4W 0402 CRCW04021003F
Vishay
R4 Resistor 1.0k 1% 1/4W 0402 CRCW04021001F
R5 Resistor 100k 1% 1/4W 0402 CRCW04021003F
R6 Resistor 100k 1% 1/4W 0402 CRCW04021003F
R7 Resistor 100k 1% 1/4W 0402 CRCW04021003F
J1 4-Pin Socket Connector 4 Pin 277-1273-ND
J2 6-Pin Socket Connector 6 Pin 277-1274-ND
S1 Jumper Stand Switch 2mm Jumper S2105-40-ND
D1 Green LED 1206 L62215CT-ND Chicago Miniature
D2 3.0A Schottky Diode SMA B340LADITR-ND Diodes Incorporated
AAT3682
DATA SHEET
Li-Ion/Polymer Linear Battery Charger
18 Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201884A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 17, 2012
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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works may change its documentation, products, services, specifi cations or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for confl icts, incompatibilities, or other diffi culties arising from any future changes.
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifi cations as a result of design defects, errors, or operation of products outside of pub-
lished parameters or design specifi cations. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifi cations or parameters.
Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
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1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
Ordering Information
Output Voltage Package Marking1Part Number (Tape and Reel)2
4.2V QFN44-16 MGXXY AAT3682ISN-4.2-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 Information3
4.000
±
0.050
Pin 1 Dot By Marking
2.400
±
0.050
0.550
±
0.020
2.400
±
0.050
4.000
±
0.050 2.280 REF
0.650 BSC
0.900
±
0.100
Pin 1 Identification
C0.3
1
4
58
9
13 16
0.025
±
0.025
0.214
±
0.036
0.330
±
0.075
Top View Bottom View
Side View
All dimensions in millimeters.
