Analogic AAT3682ISN-4.2-T1 Lithium-ion/polymer linear battery charger Datasheet

AAT3682
Lithium-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 the sleep mode option for
when the input supply is removed. In this mode, it
draws only 2.0µA of typical current.
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The AAT3682 is available in a 16-pin QFN44 and is
specified over the -20°C to +70°C temperature
range.
BatteryManager™
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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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
Pin Description
Pin #
Symbol
1
2, 3, 8, 12
4
TS
N/C
STAT
5
6
7
VSS
DRV
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 2.2kΩ from STAT to VIN
for a visual monitor battery charge state or connect to a microcontroller to monitor battery status. A 100kΩ 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)
AAT3682
12
N/C
11
GATE
10
VSS
9
BAT
8
7
6
5
N/C
T2X
DRV
VSS
2
13
STAT
4
14
3
VP
CSI
N/C
15
2
BSENSE
N/C
16
1
VCC
TS
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AAT3682
Lithium-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
V
V
V
V
°C
Value
Units
50
2.0
°C/W
W
Thermal Information
Symbol
θJA
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.
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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
Electrical Characteristics1
VIN = 5.0V, TA = -20 to +70°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
VIN
ICC
ISLEEP
ISTAT(HI)
VSTAT(LOW)
Description
Operation Input Voltage
Operating Current
VIN
Sleep Mode Current
VIN
STAT High Level Output Leakage Current VIN
STAT Low Level Sink Current
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
Conditions
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
V
mV
A
V
mV
30.9 %VCC
61.8 %VCC
24
mV
4.182
V
4.5
V
V
%VCS
1. The AAT3682 output charge voltage is specified over 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.
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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
Typical Characteristics
Regulated Output Voltage vs. Charge Current
Battery Recharge Threshold Voltage
vs.Temperature
(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
400
500
600
700
Regulated Output Voltage vs. Temperature
(RSENSE = 0.15Ω)
(RSENSE = 0.15Ω)
Regulated Output Voltage (V)
Regulated Output Voltage (V)
300
Regulated Output Voltage vs. Input Voltage
4.40
4.30
4.20
4.10
4.00
4.0
4.5
5.0
5.5
6.0
4.250
4.225
4.200
4.175
4.150
4.125
4.100
-50
6.5
-25
Input Voltage (V)
Trickle Charge Threshold Voltage
vs.Temperature
3.3
3.2
3.1
3.0
2.9
0
25
50
Temperature (°C)
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50
75
100
(RSENSE = 0.15Ω)
3.4
-25
25
Trickle Charge Current vs. Temperature
(RSENSE = 0.15Ω)
2.8
-50
0
Temperature (°C)
Trickle Charge Current (mA)
Trickle Charge Threshold Voltage (V)
200
Charging Current (mA)
Temperature (°C)
75
100
170
165
160
155
150
145
140
135
130
-50
-25
0
25
50
75
100
Temperature (°C)
5
AAT3682
Lithium-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)
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.15Ω with External Schottky)
(RSENSE = 0.15Ω; 1.8X Mode)
Trickle Charge Current (mA)
Charging Current (mA)
5.5
Charging Current vs. Battery Voltage
700
600
VIN = 5.5V
VIN = 4.5V
500
VIN = 4.75V
400
300
200
100
0
2.5
3.0
3.5
4.0
Battery Voltage (V)
6
5.0
6.0
Input Voltage (V)
4.5
5.0
170
165
160
155
150
145
140
135
130
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
Typical Characteristics
Charging Current vs. Input Voltage
Trickle Charge Current vs. Input Voltage
(RSENSE = 0.2Ω with External Schottky)
(RSENSE = 0.2Ω; 1.8X Mode)
Trickle Charge Current (mA)
Charging Current (mA)
600
500
400
VBAT = 4.0V
300
200
VBAT = 3.6V
100
0
4.0
4.5
5.0
5.5
104
102
100
98
96
94
4
6.0
4.5
5
Input Voltage (V)
Safe Operating Area
(TJ(MAX) = 120°C)
(RSENSE = 0.2Ω with External Schottky)
Maximum Input Voltage (V)
Charging Current (mA)
600
500
400
VIN = 4.5V
VIN = 5.5V
200
VIN = 4.75V
100
0
2.5
3.0
3.5
6
Input Voltage (V)
Charging Current vs. Battery Voltage
300
5.5
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)
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AAT3682
Lithium-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.
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AAT3682
Lithium-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.
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.
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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
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.
(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.
Constant Current Charging
Charge Inhibit
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.
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.
Constant Voltage Charging
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.
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
10
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.
Resuming Charge and the VRCH
Threshold
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
3682.2005.02.1.1
AAT3682
Lithium-Ion/Polymer Linear Battery Charger
system. This is done to prevent the charger from
erroneously 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 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.
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
Charge Status
status word will take four seconds to display
through an LED. The five modes include:
1. Sleep/Charge Complete: The IC goes into
Sleep mode when no battery is present -ORwhen 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 detected at the BAT pin -OR- when a
battery Over-Temperature fault is detected
on the TEMP pin.
3. Battery Conditioning: When the charge system is in the 1X or 2X trickle charge mode.
4. Constant Current (CC) Mode: When the system is in the constant current charge mode.
5. Constant Voltage (CV) Mode: When the system is in the 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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11
AAT3682
Lithium-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 power-up sequence. The T2X pin should be
pulled high with the use of a 100kΩ resistor. If the
input supply to VIN will not exceed 5.5V, then the
T2X pin may be tied directly to VIN through a
100KΩ 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
Charge Status
Sleep / Charge Complete
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 recording
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 Sleep/Charge
Complete mode. In addition, the T2X input must be
tied to VCC through a 100kΩ 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 out as the battery becomes fully
charged (see Figure 5).
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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AAT3682
Lithium-Ion/Polymer Linear Battery Charger
VIN
R2
2
1
C1
22µF
J1
GND
0.2Ω
R1
2.2K
R5
100K
13
14
15
16
C5
4.7µF
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.
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 overvoltage 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-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.
3682.2005.02.1.1
Applications Information
Choosing a Sense Resistor
The charging rate recommended by Lithium-Ion
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
Characteristic table as VCS. To program a nominal
500mA charge current during fast-charge, a
200mΩ value resistor should be selected.
13
AAT3682
Lithium-Ion/Polymer Linear Battery Charger
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 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
5 • RTH • RTC
RT1 = 3 • (R - R )
TC
TH
5 • RTH • RTC
RT2 = (2 • R ) - (7 • R )
TC
TH
RT1 and RT2 for use with PTC Thermistor
5 • RTH • RTC
RT1 = 3 • (R - R )
TC
TH
5 • RTH • RTC
RT2 = (2 • R ) - (7 • R )
TH
TC
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 tem-
14
perature-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 undervoltage 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 adaptor,
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 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 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.
3682.2005.02.1.1
AAT3682
Lithium-Ion/Polymer Linear Battery Charger
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
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.
AAT3682 features 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.
3682.2005.02.1.1
Charge Status
LED Display
No battery connected
Battery condition
cc
cv
Sleep/charge complete
blinking
100% LED light
75% LED light
25% LED light
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 100KΩ resistor.
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.
Charge Status
LED Display
No battery connected
Battery condition
cc
cv
Sleep/charge complete
Blinking
On
On
On
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.
15
AAT3682
Lithium-Ion/Polymer Linear Battery Charger
PD(MIN) =
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 to
save cost if sufficient input power supply head
room 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.
First, one must determine the appropriate minimum
diode forward voltage drop. Refer to the following
equation:
VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE)
VF
ICC
Where:
PD(MIN) = Minimum power rating for a diode selection
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 circuit. A Schottky diode allows
for lower power dissipation, smaller component
package sizes, and greater circuit layout densities.
Where:
VIN(MIN) = Minimum input supply level
Rectifier Diodes
VBAT(MAX) = Maximum battery charge voltage required
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.
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 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):
16
3682.2005.02.1.1
AAT3682
Lithium-Ion/Polymer Linear Battery Charger
Figure 6: Evaluation Board Top Side Layout.
Figure 7: Evaluation Board Bottom Side Layout.
Reference
Component
Designator Description
U1
C1
C2
C3
R1
R2
R3
R4
R5
R6
R7
J1
J2
S1
D1
D2
3682.2005.02.1.1
Footprint
Battery Charger AAT3682
QFN44-16
Ceramic Capacitor 20µF-10V-X5R
1210
Ceramic Capacitor 10µF-10V-X5R
0805
Ceramic Capacitor 0.047µF-10V-X7R
0805
Resistor 2.2KΩ 1/4W
0402
Current Sensing Resistor 0.2Ω 1/4W
0805
Resistor 1.0KΩ 1% 1/4W
0402
Resistor 1.0KΩ 1% 1/4W
0402
Resistor 100KΩ 1% 1/4W
0402
Resistor 100KΩ 1% 1/4W
0402
Resistor 100KΩ 1% 1/4W
0402
4-Pin Socket Connector
4 Pin
6-Pin Socket Connector
6 Pin
Jumper Stand Switch
2 mm Jumper
Green LED
1206
3.0A Schottky Diode
SMA
Part Number
Manufacturer
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
AnalogicTech
muRata
muRata
Vishay
Vishay
SSM Susumu
Vishay
Vishay
Vishay
Vishay
Vishay
Chicago Miniature
Diodes Incorporated
17
AAT3682
Lithium-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
0.330 ± 0.050
Pin 1 Identification
13
16
0.650 BSC
1
R0.030Max
4
9
8
4.000 ± 0.050
2.400 ± 0.050
5
2.280 REF
Top View
0.0125 ± 0.0125
Bottom View
0.203 ± 0.025
0.900 ± 0.050
4.000 ± 0.050
Pin 1 Dot By Marking
0.450 ± 0.050
0.600 ± 0.050
Package Information
Side View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
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performed.
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830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
18
3682.2005.02.1.1
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