201884B.pdf

DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
General Description
Features
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 regulates battery charge voltage and charge current, and
offers an integrated pass device, minimizing the number
of external components required.
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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 carefully monitored for fault conditions. A battery charge
stable monitor output pin is provided to indicate the battery 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 temperature range.
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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
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Cellular Telephones
Digital Still Cameras
Hand-Held PCs
MP3 Players
Personal Data Assistants (PDAs)
Typical Application
BAT
VP
Adapter
RSENSE
BATT+
R3
COUT = 1μF
T2X
Gate
VP
R4
DRV
BSENSE
BATTR T1
CSI
TS
VCC
STAT
C IN = 10μF
VSS
TEMP
LED 1
R2 = 1K
RT2
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1
DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Pin Descriptions
Pin #
Symbol
1
2, 3, 8, 12
TS
N/C
4
STAT
5
6
VSS
DRV
7
T2X
9
BAT
10
11
13
14
15
16
EP
VSS
GATE
VP
CSI
BSENSE
VCC
Function
Battery temperature sense input.
Not connected.
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.
Common ground connection.
Battery charge control output.
Battery trickle charge control input. Connect this pin to VSS to double the battery trickle charge current. Leave this pin floating for normal trickle current (10% of full charge current). To enter microcontroller fast-read status, pull this pin high during power up.
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.
Common ground connection.
Input voltage for biasing the pass device.
Battery charge power input.
Current sense input.
Battery voltage sense input.
AAT3682 bias input power.
Exposed paddle (bottom); connect to GND directly beneath the package.
Pin Configuration
QFN44-16
(Top View)
13
15
14
BSENSE
16
1
12
N/C
N/C
2
11
GATE
N/C
3
10
VSS
STAT
4
9
BAT
AAT3682
8
7
6
5
N/C
T2X
DRV
VSS
2
VP
CSI
VCC
TS
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Absolute Maximum Ratings1
Symbol
Description
VIN
VCSI
VT2X
Bias, VBAT
TJ
VIN Relative to GND
CSI to GND
T2X to GND
BAT to GND
Operating Junction Temperature Range
Value
Units
-0.3 to 6.0
-0.3 to VCC + 0.3
-0.3 to 5.5
-0.3 to VCC + 0.3
-40 to 85
°C
Value
Units
50
2.0
°C/W
W
V
Thermal Information
Symbol
JA
PD
Description
Maximum Thermal Resistance2, 3
Power Dissipation (TA = 25°C)
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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Electrical Characteristics1
VIN = 5.0V, TA = -20°C to +70°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
VIN
ICC
ISLEEP
ISTAT(HI)
VSTAT(LOW)
Description
Conditions
Operation Input Voltage
Operating Current
Sleep Mode Current
STAT High Level Output Leakage Current
STAT Low Level Sink Current
VIN
VIN
VIN
VIN
VCH
Output Charge Voltage Regulation
VCS
ICH
VMIN
Charge Current Regulation
Charge Current2
Preconditioning Voltage Threshold
Trickle Charge Current Regulation
Trickle Charge Current Gain
Low Temperature Threshold
High Temperature Threshold
Charge Termination Threshold Voltage
Battery Recharge Voltage Threshold
Under-Voltage Lockout
Over-Voltage Protection Threshold
Over-Current Protection Threshold
VTRICKLE
T2X
VTS1
VTS2
VTERM
VRCH
VUVLO
VOVP
VOCP
Min
Typ
4.7
=
=
=
=
5.5V, VCH = 4.2
3.5V, VCH = 4.2
5.5V
5.5V, ISINK = 5mA
TA = 25°C
VBAT = 4.2V
See Note 1
VIN = 5.5V, VCH = 4.2
VIN = 5.5V
VCH = 4.2V
T2X Floating; VCH = 4.2V
T2X = VSS
VCH = 4.2V
VIN Rising, TA = 25°C
0.5
3.0
-1.0
4.175
4.158
90
3.04
29.1
58.2
4
4.018
3.5
0.3
4.20
4.20
100
3.1
10
1.8
30
60
12
4.1
4.0
4.4
200
Max
Units
6.0
3.0
6.0
+1.0
0.6
4.225
4.242
110
1.0
3.16
V
mA
μA
μA
V
30.9
61.8
24
4.182
4.5
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mV
A
V
mV
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.
4
V
%VCC
%VCC
mV
V
V
V
%VCS
DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Typical Characteristics
Battery Recharge Threshold Voltage
vs.Temperature
Regulated Output Voltage vs. Charge Current
(RSENSE = 0.15Ω))
Regulated Output Voltage (V)
Battery Recharge
Threshold Voltage (V)
(RSENSE = 0.15Ω)
4.20
4.15
4.10
4.05
4.00
3.95
3.90
3.85
3.80
-25
-50
0
25
50
75
4.25
4.23
4.21
4.19
4.17
4.15
100
0
100
200
Temperature (°C)
Regulated Output Voltage vs. Input Voltage
Regulated Output Voltage (V)
Regulated Output Voltage (V)
4.30
4.20
4.10
4.00
5.0
5.5
6.0
4.200
4.175
4.150
4.125
4.100
-50
-25
Trickle Charge Current (mA)
Trickle Charge Threshold Voltage (V)
3.2
3.1
3.0
2.9
Temperature (°C)
50
75
100
(RSENSE = 0.15Ω)
3.3
50
25
Trickle Charge Current vs. Temperature
3.4
25
0
Temperature (°C)
(RSENSE = 0.15Ω)
0
700
4.225
6.5
Trickle Charge Threshold Voltage
vs.Temperature
-25
600
4.250
Input Voltage (V)
2.8
-50
500
(RSENSE = 0.15Ω)
4.40
4.5
400
Regulated Output Voltage vs. Temperature
(RSENSE = 0.15Ω)
4.0
300
Charging Current (mA)
75
100
170
165
160
155
150
145
140
135
130
-50
-25
0
25
50
75
100
Temperature (°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Typical Characteristics
Charging Current vs. Temperature
Charging Current vs. Input Voltage
(RSENSE = 0.15Ω)
(RSENSE = 0.15Ω with External Schottky)
700
Charging Current (mA)
Charging Current (mA)
700
690
680
670
660
650
-50
-25
0
25
50
75
600
500
VBAT = 4.1V
400
300
VBAT = 3.6V
200
100
0
4.0
100
4.5
Temperature (°C)
Charging Current vs. Battery Voltage
Trickle Charge Current (mA)
Charging Current (mA)
600
VIN = 5.5V
VIN = 4.75V
400
300
200
100
0
2.5
3.0
3.5
4.0
4.5
170
165
160
155
150
145
140
135
130
5.0
4.0
4.5
Battery Voltage (V)
VBAT = 4.0V
300
VBAT = 3.6V
100
5.0
Input Voltage (V)
6
Trickle Charge Current (mA)
Charging Current (mA)
500
4.5
6.0
(RSENSE = 0.2Ω; 1.8X Mode)
600
0
4.0
5.5
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.2Ω with External Schottky)
200
5.0
Input Voltage (V)
Charging Current vs. Input Voltage
400
6.0
(RSENSE = 0.15Ω; 1.8X Mode)
700
VIN = 4.5V
5.5
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.15Ω with External Schottky)
500
5.0
Input Voltage (V)
5.5
6.0
104
102
100
98
96
94
4
4.5
5
5.5
Input Voltage (V)
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Typical Characteristics
Charging Current vs. Battery Voltage
Safe Operating Area
(RSENSE = 0.2Ω with External Schottky)
(TJ(MAX) = 120°C)
Maximum Input Voltage (V)
Charging Current (mA)
600
500
400
VIN = 4.5V
300
VIN = 5.5V
200
VIN = 4.75V
100
0
2.5
3.0
3.5
4.0
4.5
5.0
7.0
6.0
5.0
TAMB = 85°C
4.0
TAMB = 70°C
TAMB = 40°C
TAMB = 50°C
3.0
2.0
1.0
Schottky VF = 0.2V
0.0
0.0
0.2
0.4
0.6
0.8
Charging Current (A)
Battery Voltage (V)
Safe Operating Area
Maximum Input Voltage (V)
(TJ(MAX) = 150°C)
6.2
6.0
5.8
TAMB = 85°C
5.6
TAMB = 70°C
5.4
TAMB = <50°C
5.2
Schottky VF = 0.2V
5.0
0
0.2
0.4
0.6
0.8
Charging Current (A)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Functional Block Diagram
VP
BAT
GATE
T2X
2X Trickle
Charge
Control
Loop Select
MUX
Driver
DRV
CSI
Current Loop
Error Amp
Microcontroller
Status Generator
STAT
VREF
Voltage Loop
Error Amp
Charge Status
Logic Control
MUX
BSENSE
LED Signal
Generator
Voltage
Comparator
Microcontroller
Read Enable
TS
VCC
T2X
VSS
Temperature
Sense
Comparator
Power-On
Reset
Under-Voltage
Lock Out
Over-Current /
Short-Circuit
Protection
Functional Description
Cell Preconditioning
The AAT3682 is a linear charger designed for single-cell
lithium-ion/polymer batteries. It is a full-featured battery 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.
Before the start of charging, the AAT3682 checks several conditions in order to maintain a safe charging environment. The input supply must be above the minimum
operating voltage, or under-voltage lockout threshold
(VUVLO), for the charging sequence to begin. Also, the cell
temperature, as reported by a thermistor connected to
the TS pin, must be within the proper window for safe
charging.
8
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Power On Reset
Power On Reset
UVLO
No
VCC > VUVLO
Shut Down
Shut Down
Mode
Mode
Yes
Temperature
Temperature
Fault
Fault
No
Temperature Test
TS > VTS1
TS < VTS2
Yes
Preconditioning Test
VMIN > VBAT
Yes
Low Current
Conditioning
Low Current
Charge
Conditioning
(Trickle
Charge)
Charge
No
Current Phase Test
VCH > VBAT
Yes
Current
Current
Charging
Charging
Mode
Mode
No
Voltage
Phase Test
VTERM
< I BAT
RSENSE
Yes
Voltage
Voltage
Charging
Charging
Mode
Mode
No
< VRCH
Charge Complete
Charge Complete
Latch Off
Latch Off
Figure 1: AAT3682 Operational Flow Chart.
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Preconditioning
(Trickle Charge)
Phase
Constant Voltage Charging
Constant Current
Phase
Constant Voltage
Phase
Output Charge
Voltage (VCH)
Preconditioning
Voltage Threshold
(VMIN)
Regulation
Current
(ICHARGE(REG))
Charge Cycle Termination,
Recharge Sequence
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 performed 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 transistor 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 feedback for the current control loop. The AAT3682 remains
in constant current charge mode until the battery reaches the voltage regulation point, VCH.
10
When the battery voltage reaches VCH during constant
current mode, the AAT3682 transitions to constant voltage 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.
After the charge cycle is complete, the AAT3682 shuts
off the pass device and automatically enters powersaving 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 voltage) or the AAT3682 is reset by cycling the input supply
through the power-on sequence. Falling below VRCH signals the IC that it is time to initiate a new charge cycle.
Sleep Mode
When the input supply is disconnected, the device automatically enters power-saving sleep mode. Only consuming 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 applications.
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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Resuming Charge and the VRCH Threshold
LED Display Charge Status Output
The AAT3682 will automatically resume charging under
most conditions when a battery charge cycle is interrupted. 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 voltage and automatically resume charging in the appropriate 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 charger from a USB bus supply. It is also beneficial for charging 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 erroneously turning on and off once a battery charge cycle is
complete.
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 display through an LED. The five modes include:
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 battery under charge is in the constant current mode and
the cell voltage is 3.7V when the input supply is inadvertently removed and then restored. The battery is below
the VRCH threshold and the charge cycle will immediately
resume where it left off.
Charge Status
1.
2.
3.
4.
5.
Sleep/Charge Complete: The IC goes into Sleep
mode when no battery is present -OR- when the
charge cycle is complete.
Fault: When an over-current (OC) condition is
detected by the current sense and control circuit
-OR- when an over-voltage (OV) condition is detected at the BAT pin -OR- when a battery over-temperature fault is detected on the TEMP pin.
Battery Conditioning: When the charge system is in
1X or 2X trickle charge mode.
Constant Current (CC) Mode: When the system is in
constant current charge mode.
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 periods. See Figure 3 below.
LED Display
Output Status
on/off
on/off
on/off
on/off
ON
Sleep / Charge Complete
off / off / off / off
Temp., OC, OV Fault
on / on / off / off
Battery Conditioning
on / on / on / on
Constant Current Mode
on / on / on / off
Constant Voltage Mode
on / off / off / off
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Figure 3: LED Display Output.
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
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 highspeed 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 control 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 configuration, the LED will be illuminated for all modes except the
Charge Status
Sleep / Charge Complete
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 addition to battery temperature monitoring, the IC constantly 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 overcurrent 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 overvoltage 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-current or over-voltage event, the STAT will report a FAULT
signal. In the event of a battery over-temperature condition, 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.
Output Status
STAT Level
HI / HI / HI / HI
Temp., OC, OV Fault
LO / LO / HI / HI
Battery Conditioning
LO / LO / LO / LO
Constant Current Mode
LO / LO / LO / HI
Constant Voltage Mode
LO / HI / HI / HI
Figure 4: Microcontroller Interface Logic Output.
12
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
VIN
2
1
C1
22μF
R1
2.2K
R5
100K
C5
4.7μF
13
14
15
16
J1
GND
R2
0.2Ω
N/C
GATE
VSS
BAT
12
11
10
9
J2
D1
8
7
6
5
R6
100K
Remove capacitor for
progressive dimming
TS
N/C
N/C
STAT
3
100K
1
C2
10μF
1
2
3
R4
1K
C3
47nF
R7
C4
1000pF
R3
1K
N/C
T2X
DRV
VSS
D2
Green LED
VP
CSI
BSENSE
VCC
1
2
3
4
U1
AAT3682
S1
2
SW-T2X
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 determine the maximum allowable charge current for a given
input voltage. The current sense resistor, RSENSE, programs
the charge current according to the following equation:
RSENSE =
VCC - VCSI
ICHARGE
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:
P=
VCS2
0.1V2
=
= 50mW
RSENSE
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 resistor 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
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13
DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
that the voltage at TS is within a voltage window bounded by VTS1 and VTS2. Please see the following equations
for specifying resistors:
RT1 and RT2 for use with NTC Thermistor:
RT1 =
RT2 =
5 ∙ RTH ∙ RTC
3 · (RTC - RTH)
5 ∙ RTH ∙ RTC
(2 ∙ RTC) - (7 ∙ RTH)
RT1 and RT2 for use with PTC Thermistor:
RT1 =
RT2 =
5 ∙ RTH ∙ RTC
3 · (RTH - RTC)
5 ∙ RTH ∙ RTC
(2 ∙ RTH) - (7 ∙ RTC)
Where RTC is the thermistor’s cold temperature resistance and RTH is the thermistor’s hot temperature resistance. See thermistor specifications for additional information. 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 decoupling 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 stability of the device itself. However, a capacitor connected
14
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 discharge 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 internal power dissipation. The maximum power dissipation
occurs when the input voltage is at a maximum and the
battery voltage is at the minimum preconditioning voltage threshold. This power is then multiplied times the
package theta to determine the maximum junction temperature. The worst case power junction temperature is
calculated as follows:
PMAX = (VIN(MAX) - VSENSE - VSCHOTTKY - VBAT(MIN)) ⋅ ICHG(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.
VIN(MAX) =
=
TJ(MAX) - TAMB
+ VBAT + VSCHOTTKY + VCS
θ ⋅ ICHG(MAX)
120°C - 70°C
+ 3.1V + 0.2V + 0.1V
50°C/W ⋅ 500mA
= 5.3V
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 quickly 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
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
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 applications, where it might not be desirable to have a “charger ready” blinking LED, a large COUT capacitor in the
range of 100μF or more would prevent the operation of
this mode.
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.
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.
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.
Charge Status
LED Display
No Battery Connected
Battery Condition
Constant Current
Constant Voltage
Sleep/Charge Complete
Blinking
100% LED Light
75% LED Light
25% LED Light
Off
Table 1: Charging Status.
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 voltage, and cost.
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.
First, one must determine the appropriate minimum
diode forward voltage drop:
As the battery is transitioning from trickle charge to constant 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.
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
Charge Status
LED Display
No Battery Connected
Battery Condition
Constant Current
Constant Voltage
Sleep/Charge Complete
Blinking
On
On
On
Off
VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE)
Where:
Based on the maximum constant current charge level set
for the system, the next step is to determine the minimum 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 current amplitude and the diode forward voltage (VF):
Table 2: Charging Status With C3 Connected.
PD(MIN) =
VF
ICC
Where:
Reverse Current Blocking Diode
PD(MIN) = Minimum power rating for a diode selection
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15
DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
VF = Diode forward voltage
ICC = Constant current charge level for the system
Rectifier 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 circuit. A Schottky diode allows for lower power dissipation,
smaller component package sizes, and greater circuit
layout densities.
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.
Figure 6: Evaluation Board Top Side Layout.
Figure 7: Evaluation Board Bottom Side Layout.
Schottky Diodes
16
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DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Reference
Symbol
Description
Footprint
Part Number
Manufacturer
U1
C1
C2
C3
R1
R2
R3
R4
R5
R6
R7
J1
J2
S1
D1
D2
Battery Charger AAT3682
Ceramic Capacitor 20μF-10V-X5R
Ceramic Capacitor 10μF-10V-X5R
Ceramic Capacitor 0.047μF-10V-X7R
Resistor 2.2k 1/4W
Current Sensing Resistor 0.2 1/4W
Resistor 1.0k 1% 1/4W
Resistor 1.0k 1% 1/4W
Resistor 100k 1% 1/4W
Resistor 100k 1% 1/4W
Resistor 100k 1% 1/4W
4-Pin Socket Connector
6-Pin Socket Connector
Jumper Stand Switch
Green LED
3.0A Schottky Diode
QFN44-16
1210
0805
0805
0402
0805
0402
0402
0402
0402
0402
4 Pin
6 Pin
2mm Jumper
1206
SMA
AAT3682-4.2
GRM32ER61A226KA65L
GRM21BR61A106KE19L
VJ0805Y473KXQA
CRCW04022211F
RL1220S-R20-F
CRCW04021003F
CRCW04021001F
CRCW04021003F
CRCW04021003F
CRCW04021003F
277-1273-ND
277-1274-ND
S2105-40-ND
L62215CT-ND
B340LADITR-ND
Skyworks
Murata
Vishay
SSM Susumu
Vishay
Chicago Miniature
Diodes Incorporated
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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17
DATA SHEET
AAT3682
Li-Ion/Polymer Linear Battery Charger
Ordering Information
Output Voltage
Package
Marking1
Part 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
2.400 ± 0.050
0.550 ± 0.020
0.330 ± 0.075
13
2.400 ± 0.050
1
4
9
8
4.000 ± 0.050
Pin 1 Identification
16
C0.3
0.650 BSC
5
2.280 REF
Top View
0.025 ± 0.025
Bottom View
0.214 ± 0.036
0.900 ± 0.100
4.000 ± 0.050
Pin 1 Dot By Marking
Side View
All dimensions in millimeters.
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.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Skyworks may change its documentation, products, services, specifications 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 conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided hereunder, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, INCLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or environmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of published parameters or design specifications. 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 specifications 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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18
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201884A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • April 17, 2012