1
AAT3681
DATA SHEET
USB Port or AC Ada
p
ter Li-Ion/Pol
y
mer Batter
y
Char
g
er
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
General Description
The AAT3681 BatteryManager is an integrated single cell
lithium-ion/polymer battery charger IC, designed to oper-
ate from a DC power source or USB port up to an input
voltage of 7.5V. It requires just one external component.
The AAT3681 precisely regulates battery charge voltage
and current for 4.2V (4.375V option) lithium-ion/poly-
mer battery cells. When charged from an AC adapter or
USB port, the battery charging current can be set by an
external resistor up to 300mA.
Battery charge state is continuously monitored for fault
conditions. In the event of an over-voltage, short-cir-
cuit, or over-temperature failure, the device will auto-
matically shut down, thus protecting the charging device,
control system, and the battery under charge. A status
monitor output pin is provided to indicate the battery
charge status by directly driving an external LED.
The AAT3681 is available in a Pb-free, thermally
enhanced, space-saving 8-pin 2.0 × 2.2mm SC70JW
package and is specified for operation over the -40°C to
+85°C temperature range.
Features
• USB or AC Adapter System Power Charger
▪ Programmable from 15mA to 300mA
• 4.0V ~ 7.5V Input Voltage Range
• High Level of Integration with Internal:
▪ Charging Device
▪ Reverse Blocking Diode
• Automatic Current Sensing
• Automatic Recharge Sequencing
• Full Battery Charge Auto Turn Off/Sleep Mode/Charge
Termination
• Shutdown Current <1μA
• Automatic Trickle Charge for Battery Pre-Conditioning
(AAT3681-1 is No Trickle Charge Option)
• Over-Voltage and Emergency Thermal Protection
• Power On Reset and Soft Start
• LED Status Pin
• 8-Pin 2.0 × 2.2mm SC70JW Package
Applications
• Bluetooth® Headsets
• DECT Headsets
• Digital Still Cameras
• MP3, Portable Music, and Portable Media Players
• Personal Data Assistants (PDAs)
• Wrist Watches
• Other Lithium-Ion/Polymer Battery-Powered Devices
Typical Application
AAT3681
C
BATT-
Battery
Pack
ADP
GND
BAT
BATT+
RSET
A
dapter/USB Input
STAT
EN
ISET
Enable
2
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Pin Descriptions
Pin # Symbol Type Function
1 EN In Enable pin. Logic high enables the IC (internally pulled down).
2 ISET In/Out Connect resistor here to set the charge current.
3 BAT In/Out Battery charging and sensing.
4 ADP Power In Input from USB/adapter charger.
5 STAT Out Open drain status pin.
6, 7, 8 GND Power Ground connection.
Pin Configuration
SC70JW-8
(Top View)
ISET
BAT
ADP
GND
GND
GND
STAT
EN 1
2
3
45
6
7
8
3
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
AAT3681 Feature Options
Product Trickle Charge
AAT3681 Yes
AAT3681-1 No
Absolute Maximum Ratings1
Symbol Description Value Units
VPADP Continuous -0.3 to 8.0 V
VNBAT, STAT, ISET, EN -0.3 to VP + 0.3
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at Leads) 300
Thermal Information2
Symbol Description Value Units
PDMaximum Power Dissipation 0.687 W
JA Maximum Thermal Resistance 160 °C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
4
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Electrical Characteristics1
VADP = 5V, TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol Description Conditions Min Typ Max Units
Operation
VADP Adapter Voltage Range 4.0 7.5 V
VUVLO Under-Voltage Lockout (UVLO) Rising Edge 3 4
UVLO Hysteresis 150 mV
IOP Operating Current Charge Current = 200mA 0.5 1 mA
ISHUTDOWN Shutdown Current VBAT = 4.25V, EN = GND 0.3 1 μA
ILEAKAGE Reverse Leakage Current from BAT Pin VBAT = 4V, ADP Pin Open 0.4 2
Voltage Regulation
VBAT_EOC End of Charge Accuracy 4.158 4.20 4.242 V
VCH/VCH Output Charge Voltage Tolerance 0.5 %
VMIN Preconditioning Voltage Threshold AAT3681 Only 2.85 3.0 3.15 V
VRCH Battery Recharge Voltage Threshold Measured from VBAT_EOC -0.1
Current Regulation
ICH Charge Current Programmable Range 15 300 mA
ICH/ICH Charge Current Regulation Tolerance 10 %
VSET ISET Pin Voltage 2V
KI_A Current Set Factor: ICH/ISET 800
Charging Devices
RDS(ON) Charging Transistor On-Resistance VADP = 5.5V 0.9 1.1
Logic Control/Protection
VEN(H) Input High Threshold 1.6
VVEN(L) Input Low Threshold 0.4
VSTAT Output Low Voltage STAT Pin Sinks 4mA 0.4
ISTAT STAT Pin Current Sink Capability 8mA
VOVP Over-Voltage Protection Threshold 4.4 V
ITK/ICH Pre-Charge Current ICH = 100mA; AAT3681 Only 10 %
ITERM/ICH Charge Termination Threshold Current 10
1. The AAT3681 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -40°C to +85°C temperature range is guaranteed by design.
5
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Typical Characteristics
RSET (kΩ
Ω
)
ICH (mA)
1
10
100
1000
1 10 100 1000
Constant Charging Current
vs. Set Resistor Values
Charging Current vs. Battery Voltage
(AAT3681 Only)
VBAT (V)
ICH (mA)
0
50
100
150
200
250
300
350
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3
RSET = 8.06kΩ
RSET = 5.36kΩ
RSET = 16.2kΩ
RSET = 31.6kΩ
Charging Current vs. Battery Voltage
(AAT3681-1 Only)
VBAT (V)
ICH (mA)
0
100
200
300
400
500
600
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3
RSET = 3.24K
RSET = 5.36K
RSET = 8.06K
RSET = 16.2K
RSET = 31.6K
End of Charge Battery Voltage
vs. Input Voltage
Input Voltage (V)
Battery Voltage (V)
4.180
4.185
4.190
4.195
4.200
4.205
4.210
4.215
4.220
4.5 5.0 5.5 6.0 6.5 7.0 7.
5
End of Charge Voltage Regulation
vs. Temperature
(RSET = 8.06kΩ
Ω
)
Temperature (
°
C)
VBAT_EOC (V)
4.17
4.18
4.19
4.20
4.21
4.22
4.23
-50 -25 0 25 50 75 100
Constant Charging Current vs. Input Voltage
(RSET = 8.06kΩ
Ω
)
Input Voltage (V)
Charging Current (mA)
120
140
160
180
200
220
240
260
280
4 4.5 5 5.5 6 6.5 7 7.5
VBAT = 3.3V
VBAT = 3.6V
VBAT = 4.0V
6
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Typical Characteristics
Constant Charging Current vs. Temperature
(RSET = 8.06kΩ
Ω
)
Temperature (
°
C)
ICH (mA)
190
193
195
198
200
203
205
208
210
-50 -25 0 25 50 75 100
Operating Supply Current vs. Set Resistor
RSET (kΩ
Ω
)
IOP (µA)
10
100
1000
1 10 100
VBAT = 2.85V
VBAT = 3.6V
Operating Current vs. Temperature
(RSET = 8.06kΩ
)
Temperature (
C)
IOP (µA)
300
350
400
450
500
550
-50 -25 0 25 50 75 100
Preconditioning Threshold Voltage
vs. Temperature
(RSET = 8.06kΩ
Ω
; AAT3681 Only)
Temperature (
°
C)
VMIN (V)
2.97
2.98
2.99
3
3.01
3.02
3.03
-50 -25 0 25 50 75 100
Preconditioning Charge Current
vs. Temperature
(RSET = 8.06kΩ
Ω
; AAT3681 Only)
Temperature (
°
C)
ITRICKLE (mA)
19.2
19.4
19.6
19.8
20.0
20.2
20.4
20.6
20.8
-50 -25 0 25 50 75 100
Preconditioning Charge Current vs. Input Voltage
(AAT3681 Only)
Input Voltage (V)
Trickle Charge Current (mA)
0
5
10
15
20
25
30
35
4 4.5 5 5.5 6 6.5 7 7.5
RSET = 5.36kΩ
RSET = 8.06kΩ
RSET = 16.2kΩ
RSET = 31.6kΩ
7
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Typical Characteristics
Recharging Threshold Voltage
vs. Temperature
(RSET = 8.06kΩ
Ω
)
Temperature (
°
C)
VRCH (V)
4.02
4.04
4.06
4.08
4.10
4.12
4.14
4.16
4.18
-50 -25 0 25 50 75 100
Shutdown Current vs. Supply Voltage
(RSET = 8.06kΩ
Ω
)
Supply Voltage (V)
Shutdown Current (nA)
0
200
400
600
800
1000
1200
1400
1600
1800
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.
5
85°C
25°C-40°C
VIH_ENABLE vs. Supply Voltage
(RSET = 8.06kΩ
Ω
)
VIN (V)
VIH_ENABLE (V)
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5
-40°C
25°C85°C
VIL_ENABLE vs. Supply Voltage
(RSET = 8.06kΩ
Ω
)
VIN (V)
VIL_ENABLE (V)
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5
-40°C
25°C
85°C
8
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Functional Description
The AAT3681 is a high performance battery charger
designed to charge single cell lithium-ion/polymer batter-
ies with up to 300mA of current from an external power
source. It is a stand-alone charging solution, with just one
external component required for complete functionality.
The AAT3681 precisely regulates battery charge voltage
and current for 4.2V lithium-ion/polymer battery cells.
The adapter/USB charge input constant current level can
be programmed up to 300mA for rapid charging applica-
tions. The AAT3681 is rated for operation from -40°C to
+85°C. In the event of operating ambient temperatures
exceeding the power dissipation abilities of the device
package for a given constant current charge level, the
charge control will enter into thermal limit.
A status monitor output pin is provided to indicate the
battery charge state by directly driving one external
LED.
Device junction temperature and charge state are fully
monitored for fault conditions. In the event of an over-
voltage or over-temperature failure, the device will auto-
matically shut down, protecting the charging device,
control system, and the battery under charge.
Charging Operation
The AAT3681 has four basic modes for the battery charge
cycle: pre-conditioning/trickle charge; constant current/
fast charge; constant voltage; and end of charge (see
Figure 1). (AAT3681-1 does not have trickle charge.)
Functional Block Diagram
Charge
Control
Current
Compare
Reverse Blocking
CV/
Precharge
Constant
Current
ADP BAT
ISET
UVLO
Over-
Temperature
Protection
Charge
Status
STAT
GND
EN
9
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Battery Preconditioning
Before the start of charging, the AAT3681 checks sev-
eral conditions in order to assure a safe charging envi-
ronment. The input supply must be above the minimum
operating voltage, or under-voltage lockout threshold
(VUVLO), for the charging sequence to begin. When these
conditions have been met and a battery is connected to
the BAT pin, the AAT3681 checks the state of the bat-
tery. If the cell voltage is below the preconditioning volt-
age threshold (VMIN), the charge control begins precon-
ditioning the cell. The battery preconditioning trickle
charge current is equal to the fast charge constant cur-
rent divided by 10. For example, if the programmed fast
charge current is 300mA, then the preconditioning mode
(trickle charge) current will be 30mA. Cell precondition-
ing is a safety precaution for deeply discharged battery
cells and also aids in limiting power dissipation in the
pass transistor when the voltage across the device is at
the greatest potential.
Constant Current Charging
Battery cell preconditioning continues until the voltage
on the BAT pin exceeds the preconditioning voltage
threshold (VMIN). At this point, the AAT3681 begins the
constant current charging phase. The charge constant
current (ICH) amplitude is programmed by the user via
the RSET resistor. The AAT3681 remains in the constant
current charge mode until the battery reaches the volt-
age regulation point, VBAT_EOC.
Constant Voltage Charging
The system transitions to a constant voltage charging
mode when the battery voltage reaches the output
charge regulation threshold (VBAT_EOC) during the con-
stant current fast charge phase. The regulation voltage
level is factory programmed to 4.2V (±0.5%). Charge
current in the constant voltage mode drops as the bat-
tery cell under charge reaches its maximum capacity.
End of Charge Cycle Termination
and Recharge Sequence
When the charge current drops to 10% of the pro-
grammed fast charge current level in the constant volt-
age mode, the device terminates charging and goes into
a sleep state. The charger will remain in a sleep state
until the battery voltage decreases to a level below the
battery recharge voltage threshold (VRCH).
Consuming very low current in sleep state, the AAT3681
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
AAT3681 input voltage drops, the device will enter sleep
state and automatically resume charging once the input
supply has recovered from the fault condition.
Constant Current
Charge Phase
Preconditioning
Trickle Charge
Phase
Charge Complete Voltage
Constant Current Mode
Voltage Threshold
Regulated Current
Trickle Charge and
Termination Threshold
I = CC / 10
I = Max CC
Battery Recharge
Voltage Threshold
Battery Discharge
Constant Voltage
Charge Phase
Constant Voltage
Charge Phase
Figure 1: Current vs. Voltage Profile During Charging Phases.
10
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
System Operation Flow Chart
Power On Reset
Power Input
Voltage
V
IN
> V
UVLO
Fault Conditions
Monitoring
OV, OT
Preconditioning
Test
V
MIN
> V
BAT
Current Phase Test
Voltage Phase Test
I
BAT
> I
TERM
No (AAT3681)
No
Yes
No
Preconditioning
(Trickle Charge)
Constant
Current Charge
Mode
Constant
Voltage Charge
Mode
Yes
Yes
Yes
Charge Completed
Charge
Control
No
Recharge Test
V
RCH
> V
BAT
Yes
No
Shut Down Yes
Enable
Yes
No
No (AAT3681-1)
V
BAT_EOC
> V
BAT
11
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Application Information
Adapter or USB Power Input
Constant current charge levels up to 300mA may be
programmed by the user when powered from a sufficient
input power source. The AAT3681 will operate from the
adapter input over a 4.0V to 7.5V range. The constant
current fast charge current for the adapter input is set
by the RSET resistor connected between ISET and ground.
Refer to Table 1 for recommended RSET values for a
desired constant current charge level.
Adapter Input Charge Inhibit and Resume
The AAT3681 has a UVLO and power on reset feature so
that if the input supply to the ADP pin drops below the
UVLO threshold, the charger will suspend charging and
shut down. When power is re-applied to the ADP pin or
the UVLO condition recovers, the system charge control
will assess the state of charge on the battery cell and will
automatically resume charging in the appropriate mode
for the condition of the battery.
Enable / Disable
The AAT3681 provides an enable function to control the
charger IC on and off. The enable (EN) pin is internally
pulled down. When pulled to a logic high level, AAT3681
is enabled. When left open or pulled to a logic low level,
the AAT3681 will be shut down and forced into the sleep
state. Charging will be halted regardless of the battery
voltage or charging state. When the device is re-enabled,
the charge control circuit will automatically reset and
resume charging functions with the appropriate charging
mode based on the battery charge state and measured
cell voltage on the BAT pin.
Programming Charge Current
The fast charge constant current charge level is user
programmed with a set resistor placed between the ISET
pin and ground. The accuracy of the fast charge, as well
as the preconditioning trickle charge current, is domi-
nated by the tolerance of the set resistor used. For this
reason, a 1% tolerance metal film resistor is recom-
mended for the set resistor function. Fast charge con-
stant current levels from 15mA to 300mA may be set by
selecting the appropriate resistor value from Table 1.
Nominal
ICHARGE (mA) Set Resistor
Value (k)
300 5.36
250 6.49
200 8.06
150 10.7
100 16.2
50 31.6
40 38.3
30 53.6
20 78.7
15 105
Table 1: RSET Values.
RSET (kΩ
Ω
)
ICH (mA)
1
10
100
1000
1 10 100 1000
Figure 2: Constant Charging Current
vs. Set Resistor Values.
Protection Circuitry
Over-Voltage Protection
An over-voltage event is defined as a condition where
the voltage on the BAT pin exceeds the maximum bat-
tery charge voltage and is set by the over-voltage pro-
tection threshold (VOVP). If an over-voltage condition
occurs, the AAT3681 charge control will shut down the
device until voltage on the BAT pin drops below VOVP
. The
AAT3681 will resume normal charging operation after
the over-voltage condition is removed.
Over-Temperature Shutdown
The AAT3681 has a thermal protection control circuit
which will shut down charging functions should the inter-
nal die temperature exceed the preset thermal limit
threshold. Once the internal die temperature falls below
the thermal limit, normal operation will resume the pre-
vious charging state.
12
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Charge Status Output
The AAT3681 provides battery charge status via a status
pin. This pin is internally connected to an N-channel
open drain MOSFET, which can be used to drive an exter-
nal LED. The status pin can indicate the following condi-
tions:
Event Description Status
No battery charging activity OFF
Battery charging via adapter or USB port ON
Charging completed OFF
Table 2: LED Status Indicator.
The LED should be biased with as little current as neces-
sary to create reasonable illumination; therefore, a bal-
last resistor should be placed between the LED cathode
and the STAT pin. LED current consumption will add to
the overall thermal power budget for the device pack-
age, hence it is good to keep the LED drive current to a
minimum. 2mA should be sufficient to drive most low-
cost green or red LEDs. It is not recommended to exceed
8mA for driving an individual status LED.
The required ballast resistor values can be estimated
using the following formulas:
(V
ADP -
V
F(LED)
)
R
1
=I
LED
Example:
(5.5V
- 2.0
V)
R
1
= = 1.75kΩ
2mA
Note: Red LED forward voltage (VF) is typically 2.0V @
2mA.
Thermal Considerations
The AAT3681 is offered in a SC70JW-8 package which
can provide up to 687mW of power dissipation when it
is properly bonded to a printed circuit board and has a
maximum thermal resistance of 160°C/W. Many consid-
erations should be taken into account when designing
the printed circuit board layout, as well as the placement
of the charger IC package in proximity to other heat
generating devices in a given application design. The
ambient temperature around the charger IC will also
have an effect on the thermal limits of a battery charg-
ing application. The maximum limits that can be expect-
ed for a given ambient condition can be estimated by the
following discussion.
First, the maximum power dissipation for a given situa-
tion should be calculated:
(T
J(MAX) -
T
A
)
P
D(MAX)
= θ
JA
Where:
PD(MAX) = Maximum Power Dissipation (W)
JA = Package Thermal Resistance (°C/W)
TJ(MAX) = Maximum Device Junction Temperature (°C)
[135°C]
TA = Ambient Temperature (°C)
Figure 3 shows the relationship of maximum power dis-
sipation and ambient temperature of AAT3681.
TA (°
°
C)
PD(MAX) (mW)
0
200
400
600
800
1000
0 20 40 60 80 100
Figure 3: Maximum Power Dissipation.
Next, the power dissipation can be calculated by the fol-
lowing equation:
PD = [(VIN - VBAT) · ICH + (VIN · IOP)]
Where:
PD = Total Power Dissipation by the Device
VIN = Input Voltage
VBAT = Battery Voltage as Seen at the BAT Pin
ICH = Constant Charge Current Programmed for the
Application
IOP = Quiescent Current Consumed by the Charger IC
for Normal Operation [0.5mA]
By substitution, we can derive the maximum charge cur-
rent before reaching the thermal limit condition (thermal
cycling). The maximum charge current is the key factor
when designing battery charger applications.
13
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
(P
D(MAX) -
V
IN
·
I
OP
)
V
IN
- V
BAT
I
CH(MAX)
=
(T
J(MAX) -
T
A
)
θ
JA
V
IN
- V
BAT
I
CH(MAX)
=
-
V
IN
·
I
OP
In general, the worst condition is the greatest voltage
drop across the charger IC, when battery voltage is
charged up to the preconditioning voltage threshold.
Figure 4 shows the maximum charge current in different
ambient temperatures.
VIN (V)
ICH(MAX) (mA)
0
50
100
150
200
250
300
4.25 4.5 4.75 5 5.25 5.5 5.75 6 6.25 6.5 6.75 7
TA = 85°C
TA = 60°C
TA = 45°C
TA = 25°C
Figure 4: Maximum Charging Current Before
Thermal Cycling Becomes Active.
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a decou-
pling capacitor between the ADP pin and GND. An input
capacitor in the range of 1μF to 22μF is recommended.
If the source supply is unregulated, it may be necessary
to increase the capacitance to keep the input voltage
above the under-voltage lockout threshold during device
enable and when battery charging is initiated. If the
AAT3681 adapter input is to be used in a system with an
external power supply source, such as a typical AC-to-
DC wall adapter, then a CIN capacitor in the range of 10μF
should be used. A larger input capacitor in this applica-
tion will minimize switching or power transient effects
when the power supply is “hot plugged” in.
Output Capacitor
The AAT3681 only requires a 1μF ceramic capacitor on
the BAT pin to maintain circuit stability. This value should
be increased to 10μF or more if the battery connection is
made any distance from the charger output. If the
AAT3681 is to be used in applications where the battery
can be removed from the charger, such as with desktop
charging cradles, an output capacitor greater than 10μF
may be required to prevent the device from cycling on
and off when no battery is present.
Printed Circuit Board
Layout Considerations
For the best results, it is recommended to physically
place the battery pack as close as possible to the
AAT3681 BAT pin. To minimize voltage drops on the PCB,
keep the high current carrying traces adequately wide.
Refer to the AAT3681 evaluation board for a good layout
example (see Figures 5 and 6).
14
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Figure 5: AAT3681 Evaluation Board Figure 6: AAT3681 Evaluation Board
Top Layer. Bottom Layer.
RED LED
D1 R1
1K
10μF
C1 2.2μF
C2
VIN(ADP)
VBAT
8.06K
R8
JP2
JP1
0Ω
EN
1
ISET
2
BAT
3
ADP
4STAT 5
GND 6
GND 7
GND 8
AAT3681
U1 (SC70JW-8)
Figure 7: AAT3681 Evaluation Board Schematic Diagram.
Component Part Number Description Manufacturer
U1 AAT3681IJS-T1 USB/ADP Battery Charger; SC70JW-8 Package Skyworks
R1 Chip Resistor 1k, 5%, 1/4W; 0603
VishayR8 Chip Resistor 8.06k, 1%, 1/4W; 0805
JP1 Chip Resistor 0, 5%, 1/4W; 0603
C1 GRM21BR61A106KE19L CER 10μF 10V 10% X5R 0805 Murata
C2 GRM21BR71A225KA01L CER 2.2μF 10V 10% X7R 0805
JP2 PRPN401PAEN Connecting Header, 2mm Zip Sullins Electronics
LED1 CMD15-21SRC/TR8 Red LED; 1206 Chicago Miniature Lamp
Table 3: AAT3681 Evaluation Board Bill of Materials.
15
AAT3681
DATA SHEET
USB Port or AC Adapter Li-Ion/Polymer Battery Charger
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201882C • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • February 7, 2013
Copyright © 2012, 2013 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
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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
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Ordering Information
Trickle Charge Package Marking1Part Number (Tape and Reel)2
Yes SC70JW-8 REXYY AAT3681IJS-4.2-T1
No SC70JW-8 STXYY AAT3681IJS-4.2-1-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
SC70JW-8
0.225
±
0.075
0.45
±
0.10
0.05
±
0.05
2.10
±
0.30
2.00
±
0.20
7
°
±
3
°
4
°
±
4
°
1.75
±
0.10
0.85
±
0.15
0.15
±
0.05
1.10 MAX
0.100
2.20
±
0.20
0.048REF
0.50 BSC 0.50 BSC 0.50 BSC
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.