ANALOGICTECH AAT3680IKS-8.4-T1

AAT3680
Lithium-Ion Linear Battery Charge Controller
BatteryManager™
Features
The AAT3680 BatteryManager™ is a member of
AnalogicTech's Total Power Management IC™
family. This device is an advanced Lithium-Ion (LiIon) battery charge and management IC, specifically designed for low cost compact portable applications. In a single 8-pin package, the AAT3680
precisely regulates battery charge voltage and
charge current. This device is capable of two trickle charge current levels controlled by one external
pin. Battery charge temperature and charge state
are carefully monitored for fault conditions. In the
event of an over current, short circuit or over temperature failure, the device will automatically shut
down, thus protecting the charging device and the
battery under charge. A battery charge state monitor output pin is provided to indicate the battery
charge status though a display LED. The battery
charge status output is a serial interface which may
also be read by a system microcontroller.
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The AAT3680 is available in an 8-pin MSOP or 12pin TSOPJW package, specified over -20 to 70°C
range.
Applications
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4.5V to 15V Input voltage range
1% Accurate Preset Voltages: 4.1V, 4.2V,
8.2V, 8.4V
Low operation current, typically 0.5mA
Programmable Charge Current
Automatic recharge sequencing
Battery temperature monitoring
Deep discharge cell conditioning
Fast trickle charge option with thermal over-ride
Full battery charge auto turn off / sleep mode
Over voltage, current and temperature
protection
Power on reset
LED Charge Status Output or System
Microcontroller serial interface
Temperature range -20 to 70°C
8 pin MSOP, 12 pin TSOPJW package
Cellular Phones
Personal Digital Assistants (PDA's)
Desktop Chargers
USB Chargers
Typical Application
VP
RSENSE
0.2Ω
Q1
FZT788B
BATT+
C2
10µF
R1
2.5k
DRV
T2X
BATT-
VP
CSI
BAT
RT1
AAT3680
VP
TS
TEMP
VSS
STAT
C1
4.7µF
D1
RT2
Battery
Pack
R2
1k
3680.2003.4.0.91
1
Preliminary Information
General Description
AAT3680
Lithium-Ion Linear Battery Charge Controller
Pin Description
Pin #
SOP, TSSOP
MSOP
Symbol
Function
1
7
CSI
Current Sense Input.
2
8
BAT
Battery voltage level sense input.
3
1
VP
Power supply input pin.
4
2
TS
Battery temperature sense input
5
3
STAT
Battery charge status output. Connect an LED in series with 2.2kΩ
from STAT to VP to monitor battery charge state.
6
4
VSS
Common ground connection.
7
5
DRV
Battery charge control output
8
6
T2X
2 x battery trickle charge control input. Connect this pin to VSS to
double the battery trickle charge current. Leave this pin floating for
normal trickle charge current (10% of full charge current). To enter
microcontroller fast-read status, pull this pin high during power-up.
Pin Configuration
MSOP-8
(Top View)
1
CSI
2
CSI
NC
T2X
DRV
VSS
TS
2
STAT
3
6
T2X
VSS
4
5
DRV
8
7
8
7
2
BAT
1
1
BAT
VP
1
2
2
TSOPJW-12
(Top View)
3
6
4
5
5
6
6
5
TS
VP
VP
VP
VP
STAT
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
Absolute Maximum Ratings
Symbol
VP
VCSI
VT2X
VBAT
TJ
TLEAD
ESD
(TA=25°C unless otherwise noted)
Description
VP relative to VSS
CSI to GND
T2X to GND
BAT to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at Leads)
ESD Rating
Value
Units
-0.3 to 16
-0.3 to VP+0.3
-0.3 to 5.5
-0.3 to VP+0.3
-40 to 150
300
Note 1
V
V
V
V
°C
°C
kV
Note: 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.
Note 1: IC devices are inherently ESD sensitive; handling precautions required.
Thermal Information
Symbol
ΘJA
ΘJA
PD
PD
Description
Maximum Thermal Resistance (TSOPJW-12) 2
Maximum Thermal Resistance (MSOP-8) 2
Maximum Power Dissipation (TSOPJW-12) 2
Maximum Power Dissipation (MSOP-8) 2
Value
Units
120
150
1.0
833
°C/W
°C/W
W
mW
Note 2: Mounted on an FR4 printed circuit board.
Recommended Operating Conditions
Symbol
VP
IDRV
T
3680.2003.4.0.91
Description
Operation Input Voltage
DRV Pin Sink Current
Ambient Temperature Range
Conditions
Min
4.5
-20
Typ
Max
Units
15
40
70
V
mA
°C
3
AAT3680
Lithium-Ion Linear Battery Charge Controller
Electrical Characteristics
(VIN = 4.5V to 15V, TA = -20 to 70°C unless otherwise noted. Typical
values are at TA=25°C)
Symbol
IP
Description
Conditions
Operating Current
VIN = 5.5V
VIN = 5.5V, VCH = 4.1V, VCH = 4.2V
VCH = 8.2V, VCH = 8.4V
VIN = 5.5V
ISLEEP
Sleep Mode Current
ISTAT(HI)
STAT high level output
leakage current
STAT low level sink current
DRV pin sink current
DRV pin output low
VSTAT(LOW)
ISINK
[email protected]
VCH
Output Charge Voltage
VCS
Charge Current Regulation
VMIN
Preconditioning Voltage Threshold
VTRICKLE
Trickle-Charge Current Regulation
T2X
VTS1
VTS2
VTERM
VRCH
VUVLO
VOVP
VOCP
Trickle Charge Current Gain
Low Temperature Threshold
High Temperature Threshold
Charge termination threshold voltage
VIN = 5.5V, ISINK = 5mA
VIN = 5.5V
ISINK = 5mA, VIN = 5.5V
T = 25°C
AAT3680-4.1 A
see note 1
TA = 25°C
AAT3680-4.2
see note 1
T = 25°C
AAT3680-8.2 A
see note 1
TA = 25°C
AAT3680-8.4
see note 1
VIN = 5.5V, VCH = 4.1V, VCH = 4.2V
VIN = 12V, VCH = 8.2V, VCH = 8.4V
AAT3680-4.1
AAT3680-4.2
AAT3680-8.2
AAT3680-8.4
V = 4.1V, VCH = 4.2V
T2X floating CH
VCH = 8.2V, VCH = 8.4V
T2X = VSS
VIN = 15V
VIN = 15V
VCH = 4.1V
VCH = 4.2V
Battery Recharge Voltage Threshold
VCH = 8.2V
VCH = 8.4V
Undervoltage Lockout
VIN rising, TA = 25°C
Over-voltage Protection Threshold
Over-current Protection Threshold
Min
Typ
0.5
2
3
Max Units
3
6
10
+1
mA
0.3
0.6
0.4
4.100
4.100
4.200
4.200
8.200
8.200
8.400
8.400
100
100
3.0
3.1
6.1
6.2
10
10
1.8
30
60
12
4.00
4.10
8.00
8.20
4.0
4.4
200
1.0
4.125
4.141
4.225
4.242
8.249
8.282
8.450
8.484
110
110
3.06
3.16
6.22
6.32
V
mA
V
-1
20
4.075
4.059
4.175
4.158
8.151
8.118
8.350
8.316
90
90
2.94
3.04
5.98
6.08
29.1
58.2
4
3.92
4.018
7.84
8.306
3.5
µA
µA
V
mV
V
mV
30.9
61.8
24
4.08
4.182
8.16
8.364
4.5
% VP
% VP
mV
V
V
V
% VCS
Note 1: The AAT3680 output charge voltage is specified over 0° to 50°C ambient temperature; operation over -20 to 70°C is guaranteed
by design.
4
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
Functional Block Diagram
Microcontroller
Read Enable
T2X
CSI
2x Trickle
Charge
Control
Loop Select
MUX Driver
Current Loop
Error Amp
DRV
Microcontroller
Status Generator
VREF
Voltage Loop
Error Amp
Charge Status
Logic Control
STAT
MUX
BAT
Voltage
Comparator
TS
VP
LED Signal
Generator
Temperature Sense
Comparator
Power-On
Reset
Under
Voltage
Lock Out
Functional Description
The AAT3680 is a Linear Charge Controller
designed for one and two cell Lithium Ion or
Lithium 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
and flow chart in this section.
Cell Preconditioning
Before starting charging, the AAT3680 checks several conditions in order to maintain a safe charging
environment. The input supply must be above the
minimum operating voltage, or undervoltage lockout threshold (VUVLO), for the charging sequence to
begin. Also, the cell temperature, as reported by a
thermistor connected to TS pin, must be within the
proper window for safe charging. When these conditions have been met, and a battery is connected
to the BAT pin, the AAT3680 checks the state of the
battery. If the cell voltage is below VMIN, the
AAT3680 begins preconditioning the cell. This is
performed by charging the cell with 10% of the programmed constant-current amount. For example if
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VSS
Over Current /
Short Circuit
Protection
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
the power dissipation in the pass transistor when
the voltage across the device is largest. The
AAT3680 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 AAT3680 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
AAT3680 begins constant-current charging (fast
charging). Current level for this mode is programmed using a current sense resistor RSENSE
between VP and CSI pins. The CSI pin monitors the
voltage across RSENSE to provide feedback for the
current control loop. The AAT3680 remains in constant current charge mode until the battery reaches
the voltage regulation point, VCH.
5
AAT3680
Lithium-Ion Linear Battery Charge Controller
Constant Voltage Charging
Charge Cycle Termination, Recharge
Sequence
When the battery's voltage reaches VCH during
constant-current mode, the AAT3680 transitions to
constant-voltage mode. The regulation voltage is
factory programmed: 4.1V and 4.2V (or 8.2V and
8.4V for two-cell applications) are available to support different anode materials in Lithium Ion cells.
In constant-voltage operation, the AAT3680 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 AAT3680
latches off the pass device and automatically enters
power-saving sleep mode. Either of two possible
conditions will bring the IC out of sleep mode: the
battery voltage at the BAT pin drops below VRCH
(recharge threshold voltage) or the AAT3680 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.
Power On Reset
Power On Reset
UVLO
No
VP > 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
Yes
Voltage
Voltage
Charging
Charging
Mode
Mode
No
Voltage
Phase Test
VTERM
< I BAT
RSENSE
No
< VRCH
Charge Complete
Charge Complete
Latch Off
Latch Off
Figure 1: AAT3680 Operational Flow Chart
6
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
Sleep Mode
When the input supply is disconnected, the charger
automatically enters power-saving sleep mode. Only
consuming an ultra-low 2µA in sleep mode, the
AAT3680 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 AAT3680 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 AAT3680
well suited for USB battery charger applications.
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
Charge Inhibit
The AAT3680 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 VP
or VSS will force the AAT3680 to turn off the pass
device and wait for a voltage between the low and
high temperature voltage thresholds.
Resuming Charge and the VRCH
Threshold
The AAT3680 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 AAT3680 will monitor the
battery voltage and automatically resume charging in
the appropriate mode based upon the measured battery cell voltage. The feature is useful for systems
with an unstable input supply which could be the case
when powering a charger from a USB bus supply.
This feature is also beneficial for charging or "topping
off" partially discharged batteries.
The only restriction on resuming charge of a battery is 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
one a battery charge cycle is complete.
For example, the AAT3680-4.2 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
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The AAT3680 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:
1. Sleep/Charge Complete: The IC goes into
Sleep mode when no battery is present -OR- When
the charge cycle is complete.
2. Fault: When an Over-Current (OC) condition is
detected by the current sense and control circuit OR- When an Over-Voltage (OV) condition is
detected at the BAT pin -OR- When a battery OverTemperature 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
AAT3680 senses there is no battery connected to
the BAT pin, the STAT output will turn the LED on
and off at a rate dependant on the size of the output capacitor being used. The LED cycles on for
two periods then remains off for two periods. See
figure 2 below.
7
AAT3680
Lithium-Ion Linear Battery Charge Controller
Charge Status
Output Status
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
LED Display
on/off
on/off
on/off
on/off
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Figure 2: LED Display Output
High Speed Data Reporting
An optional system microcontroller interface can be
enabled by pulling the T2X pin up to 4.5V to 5.5V
during power-up sequence. The T2X pin should be
pulled high with the use of a 100kΩ resistor. If the
input supply to VP will not exceed 5.5V, then the
T2X pin may be tied directly to VP 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
3 below.
Charge Status
Sleep / Charge Complete
An additional feature is the Output Status for Battery
Not Detected state. When the AAT3680 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 AAT3680
will only trickle charge at the 2x trickle charge level.
This is because the TX2 pin is pull high the enable
the high speed data reporting.
A status display LED may not be 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 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 AAT3680.
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 3: Microcontroller Interface Logic Output
8
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
RSENSE
0.2
VP
Q1
FZT788B
BATT+
C2
10µF
VP
R1
2.5k
DRV
TX2
CSI
BAT
BATT100k
RT1
AAT3680
VP
C1
4.7µF
R2
100k
VSS
TS
TEMP
STAT
RT2
C3
0.1µF
Battery
Pack
STAT
High Speed Data Reporting Application Schematic
Protection Circuitry
The AAT3680 is truly 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 AAT3680 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
Preconditioning
(Trickle Charge)
Phase
Constant Current
Phase
battery charge constant voltage threshold. The
AAT3680 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.
Constant Voltage
Phase
Output Charge
Voltage (VCH)
Preconditioning
Voltage Threshold
(VMIN)
Regulation
Current
(ICHARGE(REG))
Trickle Charge
and Termination
Threshold
Figure 4: Typical Charge Profile
3680.2003.4.0.91
9
AAT3680
Lithium-Ion Linear Battery Charge Controller
Applications Information
Choosing an External Pass Device
(PNP or PMOS)
The AAT3680 is designed to work with either a
PNP transistor or P-Channel Power MOSFET.
Selecting one or the other requires looking at the
design tradeoffs including performance versus cost
issues. Refer to the following design guide for
selecting the proper device:
PNP Transistor:
In this design example, we will use the following
conditions: VP=5V (with 10% supply tolerance),
ICHARGE(REG) = 600mA, 4.2V single cell Lithium Ion
pack. VP is the input voltage to the AAT3680, and
ICHARGE(REG) is the desired fast-charge current.
1. The first step is to determine the maximum
power dissipation (PD) in the pass transistor. Worst
case is when the input voltage is the highest and
the battery voltage is at the lowest during fastcharge (this is referred to as VMIN, nominally 3.1V
when the AAT3680-4.2 transitions from tricklecharge to constant-current mode). In this equation
VCS is the voltage across RSENSE.
PD = (VP(MAX) - VCS - VMIN) · ICHARGE(REG)
PD = (5.5V - 0.1V - 3.1V) · 600mA
PD = 1.38W
2. The next step is to determine which size package
is needed to keep the junction temperature below its
rated value, TJ(MAX). Using this value, and the maximum ambient temperature inside the system TA(MAX),
calculate the thermal resistance RθJA required:
RθJA =
(TJ(MAX) - TA(MAX))
PD
RθJA =
(150 - 40)
1.38
RθJA = 80°C/W
It is recommended to choose a package with a lower
RθJA than the number calculated above. A SOT223
package would be an acceptable choice, as it has an
RθϑΑ of 62.5°C/W when mounted to a PCB with adequately sized copper pad soldered to the heat tab.
10
3. Choose a collector-emitter (VCE) voltage rating
greater than the input voltage. In this example, VP
is 5.0V, so a 15V device is acceptable.
4. Choose a transistor with a collector current rating
at least 50% greater than the programmed
ICHARGE(REG) value. In this example we would select
a device with at least 900mA rating.
5. Calculate the required current gain (β or hFE):
βMIN =
IC(MAX)
IB(MIN)
βMIN =
0.60
0.02
βMIN = 30
where IC(MAX) is the collector current (which is the
same as ICHARGE(REG)), and IB(MIN) is the minimum
amount of base current drive shown in Electrical
Characteristics as ISINK. Important Note: The current gain (β or hFE) can vary a factor of 3 over temperature, and drops off significantly with increased
collector current. It is critical to select a transistor
with β, at full current and lowest temperature,
greater than the βMIN calculated above.
In summary, select a PNP transistor with ratings
VCE ≥ 15V, RθJA ≤ 80°C/W, IC ≥ 900mA, βMIN ≥ 30 in
a SOT223 (or better thermal) package.
P-Channel Power MOSFET:
In this design example, as shown in Figure 5, we
will use the following conditions: VP = 5V (with 10%
supply tolerance), ICHARGE(REG) = 750mA, 0.4V
Schottky diode, 4.2V single cell Lithium Ion pack.
VP is the input voltage to the AAT3680, and
ICHARGE(REG) is the desired fast-charge current.
1. The first step is to determine the maximum
power dissipation (PD) in the pass transistor. Worst
case is when the input voltage is the highest and
the battery voltage is at the lowest during fastcharge (this is referred to as VMIN, nominally 3.1V
when the AAT3680-4.2 transitions from tricklecharge to constant-current mode). In this equation
VCS is the voltage across RSENSE, and VD is the
voltage across the reverse-current blocking diode.
Refer to section below titled Schottky Diode for
further details. Omit the value for VD in the equation below if the diode is not used.
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
PD = (VP(MAX) - VCS - VD - VMIN) · ICHARGE(REG)
PD = (5.5V - 0.1V - 0.4V - 3.1V) · 750mA
PD = 1.4W
5. Calculate the required threshold voltage to deliver ICHARGE(REG):
2. The next step is to determine which size package
is needed to keep the junction temperature below its
rated value, TJ(MAX). Using this value, and the maximum ambient temperature inside the system TA(MAX),
calculate the thermal resistance RθJA required:
RθJA =
(TJ(MAX) - TA(MAX))
PD
RθJA =
(150 - 40)
1.4
RθJA = 79°C/W
It is recommended to choose a package with a lower
RθJA than the number calculated above. A SOT223
package would be an acceptable choice, as it has an
RθJA of 62.5°C/W when mounted to a PCB with adequately sized copper pad soldered to the heat tab.
3. Choose a drain-source (VDS) voltage rating
greater than the input voltage. In this example, VP
is 5.0V, so a 12V device is acceptable.
4. Choose a MOSFET with a drain current rating at
least 50% greater than the programmed
ICHARGE(REG) value. In this example we would
select a device with at least 1.125A rating.
VP
RSENSE
0.2Ω
VGS = (VCS + [email protected]) - VP(MIN)
VGS = (0.1V + 0.1V) - 4.5V
VGS = -4.3V
where VGS is the available gate to source voltage provided by the AAT3680, VCS is the voltage across the
sense resistor, [email protected] is the rated low voltage at the
DRV pin, and VP(MIN) is the worst case input voltage
(assuming 10% tolerance on the 5V supply). Choose
a MOSFET device with sufficiently low VGS(TH) so the
device will conduct the desired ICHARGE(REG).
6. Calculate the worst case maximum allowable
RDS(ON) at worst case VGS voltage:
RDS(ON) =
(VP(MIN) - VCS(MAX) - VBAT(MAX))
ICHARGE(REG)
RDS(ON) =
(4.5V - 0.11V - 4.242V)
0.75A
RDS(ON) = 197mΩ
Select a P-Channel Power MOSFET with RDS(ON)
lower than 197mΩ at VGS = -4.3V.
In summary, select a P-Channel MOSFET with ratings
VDS ≥ 12V, RθJA ≤ 79°C/W and RDS(ON) ≥ 197mΩ at
VGS = -4.3V in a SOT223 (or better thermal) package.
Q1
RFD10P03L
BATT+
R4
100k
C2
10µF
R1
1k
DRV
T2X
BATT-
VP
CSI
BAT
RT1
AAT3680
VP
TS
TEMP
VSS
STAT
C1
4.7µF
D1
RT2
Battery
Pack
R2
1k
Figure 5: Typical Applications Schematic Using P-Channel Power MOSFET
3680.2003.4.0.91
11
AAT3680
Lithium-Ion Linear Battery Charge Controller
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. The current sense resistor, RSENSE, programs the charge
current according to the following equation:
RSENSE =
(VP -VCSI)
ICHARGE(REG)
Where ICHARGE(REG) is the desired typical charge current during constant-current charge mode. VP-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. Calculate the
worst case power dissipated in the sense resistor
according to the following equation:
P=
(VCS)2
RSENSE
P=
(0.1)2
0.2
P = 50mW
be used because the AAT3680 checks to see that
the voltage at TS is within a voltage window bounded by VTS1 and VTS2. Please see equations below
for specifying resistors:
RT1 and RT2 for use with NTC Thermistor
5 · RTH · RTC
3 · (RTC - RTH)
5 · RTH · RTC
=
(2 · RTC) - (7 · RTH)
RT1 =
RT2
RT1 and RT2 for use with PTC Thermistor
5 · RTH · RTC
3 · (RTC - RTH)
5 · RTH · RTC
=
(2 · RTH) - (7 · RTC)
RT1 =
RT2
Where RTC is the thermistor's cold temperature
resistance, and RTH is the thermistor's hot temperature resistance. See thermistor specifications for
info. To ensure there is no dependence on the
input supply changes, connect divider between VP
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
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 AAT3680 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 negativetemperature coefficient thermistor (NTC) or positive-temperature coefficient thermistor (PTC) can
12
In general, it is good design practice to place a
decoupling capacitor between VP and VSS pins. An
input capacitor in the range of 0.1µF to 4.7µF 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 AAT3680 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.
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
Output Capacitor
The AAT3680 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 AAT3680 is powered up
when no battery is connected. The AAT3680 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.
Operation Under No-Load
Under no-load conditions, that is when the
AAT3680 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
AAT3680 will drop into the 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 Desk Top 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.
Reverse Current Blocking Diode
Bi-Polar Circuit Application
When using the AAT3680 with a PNP transistor, a
reverse-blocking diode is not required because
there is no current path from BAT to VP. However,
it is advisable to still place a blocking diode
between the bipolar transistor collector and the
BAT pin connection to the circuit output. In the
event where the input supply is interrupted or
removed during the constant current or constant
3680.2003.4.0.91
voltage phases of the charging cycle, the battery
under charge will discharge through the circuit
pass transistor rendering it impossible to turn off. If
the circuit is unable to turn off, the reverse leakage
will eventually discharge the battery. A blocking
diode will prevent this undesirable effect.
MOSFET Circuit Application
An reverse-blocking diode is generally required for
the circuit shown in Figure 5. For this application,
the blocking diode gives the system protection
from a shorted input, when the AAT3680 is used
with a P-Channel MOSFET. If there is no other protection in the system, a shorted input could discharge the battery through the body diode of the
pass MOSFET. If a reverse-blocking diode is
added to the system, a device should be chosen
which can withstand the maximum constant- current charge current at the maximum system ambient temperature.
Diode Selection
Typically, a Schottky diode is used in reverse current blocking applications with the AAT3680. 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 what the minimum diode
forward voltage drop must be. Refer to the following equation where:
VIN(MIN) = Minimum input supply level
VBAT(MAX) = Maximum battery charge voltage
required
VF(TRAN) = Pass transistor forward voltage drop
VF(DIODE) = Blocking diode forward voltage
VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE)
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
13
AAT3680
Lithium-Ion Linear Battery Charge Controller
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):
Where:
PD(MIN) = Minimum power rating for a diode selection
VF = Diode forward voltage
ICC = Constant current charge level for the system
PD(MIN) = VF / ICC
Schottky Diodes
The reason for selecting a Schottky diode for this
application is because Schottky diodes have a low
forward voltage drop. The forward voltage (VF) for
a Schottky diode is typically between 0.3V and
0.4V. A lower VF permits a lower voltage drop at
14
the constant current charge level set by the system, less power will be dissipated in this element of
the circuit. Schottky diode allow for lower power
dissipation, smaller component package sizes and
greater circuit layout densities.
Rectifier Diodes
Any general purpose rectifier diode can be used
with the AAT3680 application circuit in place of a
higher cost Schottky type diode. The design tradeoff is 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 a 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.
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
PCB Layout
For the best results, it is recommended to physically place the battery pack as close as possible to
the AAT3680's BAT pin. To minimize voltage drops
in the PCB, keep the high current carrying traces
Figure 6: AAT3680 Demo Board
Silk Screen / Assembly Drawing
3680.2003.4.0.91
adequately wide. For maximum power dissipation
in the pass transistor, it is critical to provide enough
copper to spread the heat. Refer to AAT3680
demo board PCB layout, see figures 6, 7 and 8
below.
Figure 7: AAT3680 Demo Board
Component Side Layout
Figure 8: AAT3680 Demo
Board Solder Side Layout
15
AAT3680
Lithium-Ion Linear Battery Charge Controller
Evaluation Board Bill of Materials
PNP Transistor Example
Designator
R3
R2
RT1
RT2
R1
C2
SW1
C1
C3
R4
U1
D1
D2
D3
Q1
Part Type
0.2Ω, 0.5 Watt
1kΩ, 5%
1MΩ, 5%
1MΩ, 5%
1.5kΩ, 5%
0.1µF
Switch
4.7µF
10µF
Not populated
Li Ion Charge Controller IC
Green LED
1.0A Schottky Diode
0.0 Ohm jumper
PNP Transistor
Footprint
Manufacturer
Part Number
1206
1206
0805
0805
0805
1206
IRC
Various
Various
Various
Various
MuRata
Mountain Switch
MuRata
MuRata
LRC1206-01-R200F
1206
1206
10JS001
GRM42-6X5R75K10
GRM42-6X5R106K16
MSOP-8
1206
SMA
AnalogicTech
Various
TSC
AAT3680IKS-4.2
SOT223
Zetex
FZT788B
Footprint
Manufacturer
Part Number
1206
1206
0805
0805
0805
1206
LRC1206-01-R200F
1206
1206
0805
MSOP-8
1206
IRC
Various
Various
Various
Various
MuRata
Mountain Switch
MuRata
MuRata
Various
AnalogicTech
Various
SMA
TO-252
TSC
Various
LL5817
P-Channel Power MOSFET Example
Designator
R3
R2
RT1
RT2
R1
C2
SW1
C1
C3
R4
U1
D1
D2
D3
Q1
16
Part Type
0.2Ω, 0.5W
1kΩ, 5%
1MΩ, 5%
1MΩ, 5%
1kΩ, 5%
0.1µF
Switch
4.7µF
10µF
100kΩ, 5%
Li Ion Charge Controller IC
Green LED
0.0 Ohm jumper
1.0A Schottky Diode
30V P-Ch MOSFET, 0.2Ω
10JS001
GRM42-6X5R75K10
GRM42-6X5R106K16
AAT3680IKS-4.2
LL5817
Various
3680.2003.4.0.91
AAT3680
Lithium-Ion Linear Battery Charge Controller
Ordering Information
Output Voltage
Package
Marking
Part Number (Tape and Reel)
MSOP-8
4.1V
AAT3680IKS-4.1-T1
MSOP-8
4.2V
AAT3680IKS-4.2-T1
MSOP-8
8.2V
AAT3680IKS-8.2-T1
MSOP-8
8.4V
AAT3680IKS-8.4-T1
TSOPJW-12
4.1V
AAT3680ITP-4.1-T1
TSOPJW-12
4.2V
AAT3680ITP-4.2-T1
TSOPJW-12
8.2V
AAT3680ITP-8.2-T1
TSOPJW-12
8.4V
AAT3680ITP-8.4-T1
Package Information
MSOP8
4° ± 4°
4.90 ± 0.10
3.00 ± 0.10
1.95 BSC
0.95 REF
0.60 ± 0.20
PIN 1
3.00 ± 0.10
0.85 ± 0.10
0.95 ± 0.15
10° ± 5°
GAUGE PLANE
0.254 BSC
0.155 ± 0.075
0.075 ± 0.075
0.65 BSC
3680.2003.4.0.91
0.30 ± 0.08
17
AAT3680
Lithium-Ion Linear Battery Charge Controller
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.10
0.20 +- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.055 ± 0.045
0.04 REF
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
18
3680.2003.4.0.91