ANALOGICTECH AAT3680ITP-4.2-T1

AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
BatteryManager™
General Description
Features
The AAT3680 BatteryManager is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. This device is a lithiumion/polymer battery charge and management IC,
specifically designed for compact portable applications. The AAT3680 precisely regulates battery
charge voltage and charge current, and 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, protecting the charging
device and the battery under charge. A battery
charge state monitor output pin is provided to indicate the battery charge status through 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 a Pb-free, 8-pin MSOP
or 12-pin TSOPJW package, specified over the
-20°C to +70°C temperature range.
Applications
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Input Voltage Range: 4.5V to 7V
1% Accurate Preset Voltages: 4.1V, 4.2V
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, Over-Current, and OverTemperature Protection
Power On Reset
LED Charge Status Output or System
Microcontroller Serial Interface
Temperature Range: -20°C to +70°C
8-Pin MSOP or 12-Pin TSOPJW Package
Cellular Phones
Desktop Chargers
Personal Digital Assistants (PDAs)
USB Chargers
Typical Application
RSENSE
0.2Ω
Q1
FZT968
SMA
BATT+
VP
B34DLA
C2
1µF
R1
1.9k
DRV
T2X
BATT-
VP
CSI
BAT
RT1
AAT3680
VP
TS
TEMP
VSS
STAT
C3
10µF
RT2
Battery
Pack
LED1
R2
1k
3680.2006.03.1.6
1
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Pin Description
Pin #
TSOPJW-12
MSOP-8
Symbol
Function
1
8
BAT
Battery voltage level sense input.
2
7
CSI
Current sense input.
3
N/A
N/C
Not connected.
4
6
T2X
2X 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.
5
5
DRV
Battery charge control output.
6
4
VSS
Common ground connection.
7
3
STAT
Battery charge status output. Connect an LED in series with 2.2kΩ
from STAT to VP to monitor battery charge state.
8, 9, 10, 11
1
VP
Power supply input pin.
12
2
TS
Battery temperature sense input.
Pin Configuration
TSOPJW-12
(Top View)
12
2
11
3
10
4
9
5
8
6
7
TS
VP
VP
VP
VP
STAT
8
BAT
7
CSI
3
6
T2X
4
5
DRV
VP
1
TS
2
STAT
VSS
2
2
1
1
BAT
CSI
N/C
T2X
DRV
VSS
MSOP-8
(Top View)
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Absolute Maximum Ratings1
TA=25°C, unless otherwise noted.
Symbol
VP
VCSI
VT2X
VBAT
TJ
ESD
Description
VP Relative to VSS
CSI to GND
T2X to GND
BAT to GND
Operating Junction Temperature Range
ESD Rating
Value
Units
-0.3 to 7.5
-0.3 to VP + 0.3
-0.3 to 5.5
-0.3 to VP + 0.3
-40 to 150
Note 2
V
V
V
V
°C
kV
Thermal Information3
Symbol
Description
ΘJA
Maximum Thermal Resistance
PD
Maximum Power Dissipation
Value
TSOPJW-12
MSOP-8
TSOPJW-12
MSOP-8
Units
120
150
1.0
833
°C/W
W
mW
Recommended Operating Conditions
Symbol
VP
IDRV
T
Description
Operation Input Voltage
DRV Pin Sink Current
Ambient Temperature Range
Conditions
Min
4.5
-20
Typ
Max
Units
7.0
40
70
V
mA
°C
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. IC devices are inherently ESD sensitive; handling precautions required.
3. Mounted on an FR4 printed circuit board.
3680.2006.03.1.6
3
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Electrical Characteristics
VIN = 4.5V to 5.5V, TA = -20°C to 70°C, unless otherwise noted; typical values are at TA = 25°C.
Symbol
IP
ISLEEP
ISTAT(HI)
VSTAT(LOW)
ISINK
[email protected]
Description
Conditions
Operating Current
Sleep Mode Current
STAT High-Level Output
Leakage Current
STAT Low-Level Sink Current
DRV Pin Sink Current
DRV Pin Output Low
VIN = 5.5V, VCH = 4.1V, VCH = 4.2V
VIN = 3.5V, VCH = 4.1V, VCH = 4.2V
VIN = 5.5V
VCH
Output Charge Voltage
VCS
Charge Current Regulation
VMIN
Preconditioning Voltage Threshold
VTRICKLE
T2X
VTS1
VTS2
VTERM
Trickle-Charge Current Regulation
Trickle Charge Current Gain
Low-Temperature Threshold
High-Temperature Threshold
Charge Termination Threshold Voltage
VRCH
Battery Recharge Voltage Threshold
VUVLO
VOVP
VOCP
Under-Voltage Lockout
Over-Voltage Protection Threshold
Over-Current Protection Threshold
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
VIN = 5.5V, VCH = 4.1V, VCH = 4.2V
AAT3680-4.1
AAT3680-4.2
T2X Floating, VCH = 4.1V, VCH = 4.2V
T2X = VSS
VIN = 5.5V
VIN = 5.5V
VCH = 4.1V
VCH = 4.2V
VIN Rising, TA = 25°C
Min
Typ
Max Units
0.5
2
3
6
+1
mA
µA
µA
0.3
0.6
0.4
4.100
4.100
4.200
4.200
100
3.0
3.1
10
1.8
30
60
12
4.00
4.10
4.0
4.4
200
1.0
4.125
4.141
4.225
4.242
110
3.06
3.16
V
mA
V
-1
20
4.075
4.059
4.175
4.158
90
2.94
3.04
29.1
58.2
4
3.92
4.018
3.5
V
mV
V
mV
30.9
61.8
24
4.08
4.182
4.5
% VP
% VP
mV
V
V
V
% VCS
1. The AAT3680 output charge voltage is specified over 0° to 50°C ambient temperature; operation over -20°C to +70°C is guaranteed
by design.
4
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
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
STAT
VREF
Voltage Loop
Error Amp
Charge Status
Logic Control
MUX
BAT
Voltage
Comparator
TS
VP
LED Signal
Generator
Temperature Sense
Comparator
Power-On
Reset
UnderVoltage
Lock Out
Functional Description
The AAT3680 is a linear charge controller designed
for single-cell lithium-ion/polymer batteries. It is a
full-featured battery management system IC with
multiple levels of integrated power savings, system
communication, and protection. Refer to the block
diagram (above) and flow chart (Figure 1) in this
section for details.
Cell Preconditioning
Before the start of 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 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.
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. For
3680.2006.03.1.6
VSS
Over-Current /
Short-Circuit
Protection
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 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
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 the 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/Polymer
Linear Battery Charge Controller
Constant Voltage Charging
Charge Cycle Termination, Recharge
Sequence
When the battery 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 are available to
support different anode materials in lithium-ion/polymer 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
Shutdown
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
(TrickleCharge
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: AAT3680 Operational Flow Chart.
6
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
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 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.
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 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. 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. This feature 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.
For example, the AAT3680-4.2 has a typical VRCH
threshold of 4.1V. A battery under charge is above
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Charge Status Output
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 -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
AAT3680 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 2.
7
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Charge Status
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 2: LED Display Output.
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.
High-Speed Data Reporting
A high-speed data reporting application schematic
is shown in Figure 3. An optional system microcontroller interface can be enabled by pulling up
the T2X pin to 4.5V to 5.5V during the 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 in high-speed data reporting, the AAT3680
will only trickle charge at the 2X trickle charge
level. This is because the TX2 pin is pulled high to
enable the high-speed data reporting.
A status display LED may not be connected to the
STAT pin when the high-speed data reporting is
being utilized. If both display modes are required,
the display LED must be switched out of the circuit
before the T2X pin is pulled high. Failing to do so
could cause problems with the high-speed switching
control circuits internal to the AAT3680.
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).
RSENSE
0.2
Q1
FZT788B
BATT+
VP
C2
10µF
VP
R1
2.5k
DRV
BATT-
TX2
100k
CSI
BAT
RT1
AAT3680
VP
TS
TEMP
C1
4.7µF
R2
100k
VSS
STAT
RT2
C3
0.1µF
Battery
Pack
STAT
Figure 3: High-Speed Data Reporting Application Schematic.
8
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Charge Status
Sleep / Charge Complete
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.
Protection Circuitry
The AAT3680 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 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
Preconditioning
(Trickle Charge)
Phase
Constant Current
Phase
maximum 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 5: Typical Charge Profile.
3680.2006.03.1.6
9
AAT3680
Lithium-Ion/Polymer
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 the lowest during
fast-charge (this is referred to as VMIN, nominally 3.1V when the AAT3680-4.2 transitions from
trickle charge to constant current mode). In this
equation, VCS is the voltage across RSENSE.
PD = (VP(MAX) - VCS - VMIN) ⋅ ICHARGE(REG)
= (5.5V - 0.1V - 3.1V) ⋅ 600mA
= 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
(150 - 40)
1.38
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 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 a 900mA rating.
5. Calculate the required current gain (β or hFE);
β > 200:
βMIN =
=
IC(MAX)
IB(MIN)
0.60
0.02
= 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 by a factor of three
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
The following conditions apply to Figure 6, for use
with the AAT3680-4.2V version: VP = 5V (with 10%
supply tolerance), ICHARGE(REG) = 750mA, 0.4V
Schottky diode, 4.2V single cell lithium-ion battery
pack. VP is the input voltage to the AAT3680, and
ICHARGE(REG) is the desired fast-charge current.
= 80°C/W
10
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
RSENSE
0.2Ω
Q1
RFD10P03L
BATT+
VP
R4
C2
10µF
100k
R1
1k
DRV
T2X
BATT-
VP
CSI
BAT
RT1
AAT3680
VP
TS
TEMP
VSS
STAT
C1
4.7µF
D1
Battery
Pack
RT2
R2
1k
Figure 6: Typical Applications Schematic Using a P-Channel Power MOSFET with the AAT3680-4.2.
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 the lowest during fast-charge
(this is referred to as VMIN, nominally 3.1V when
the AAT3680-4.2 transitions from trickle charge 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.
PD = (VP(MAX) - VCS - VD - VMIN) ⋅ ICHARGE(REG)
= (5.5V - 0.1V - 0.4V - 3.1V) ⋅ 750mA
= 1.4W
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:
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RθJA =
=
(TJ(MAX) - TA(MAX))
PD
(150 - 40)
1.4
= 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 an 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 a 1.125A rating.
11
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
5. Calculate the required threshold voltage to
deliver ICHARGE(REG):
VGS = (VCS + [email protected]) - VP(MIN)
= (0.1V + 0.1V) - 4.5V
= - 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)
(4.5V - 0.11V - 4.242V)
0.75A
= 197mΩ
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.
Choosing a Sense Resistor
The charging rate recommended by lithiumion/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
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:
12
P=
=
(VCS)2
RSENSE
(0.1)2
0.2
= 50mW
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
Select a P-channel power MOSFET with RDS(ON)
lower than 197mΩ at VGS = -4.3V.
RSENSE =
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:
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 negative
temperature coefficient thermistor (NTC) or positive temperature coefficient thermistor (PTC) can
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 the equations
below for specifying resistors:
RT1 and RT2 for use with NTC Thermistor
RT1 =
5 ⋅ RTH ⋅ RTC
3 ⋅ (RTC - RTH)
RT2 =
5 ⋅ RTH ⋅ RTC
(2 ⋅ RTC) - (7 ⋅ RTH)
(VP - VCSI)
ICHARGE(REG)
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
RT1 and RT2 for use with PTC Thermistor
RT1 =
5 ⋅ RTH ⋅ RTC
3 ⋅ (RTC - RTH)
5 ⋅ RTH ⋅ RTC
RT2 =
(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
information. To ensure there is no dependence on
the input supply changes, connect the divider
between VP and VSS. Disabling the temperaturemonitoring 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 VP 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 AAT3680 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 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 lithium-ion/polymer 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-
3680.2006.03.1.6
impedance load and assure device stability over all
operating conditions.
Operation Under No-Load Conditions
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 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.
Reverse Current Blocking Diode
Bipolar 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
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
A reverse blocking diode is generally required for
the circuit shown in Figure 6. For this application,
the blocking diode gives the system protection
from a shorted input, when the AAT3680 is used
13
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
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 if
sufficient input power supply headroom is available.
The blocking diode selection should based on merits of the device forward voltage (VF), current rating, and input supply level versus the maximum
battery charge voltage and cost.
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. Schottky
diodes allow for lower power dissipation, smaller
component package sizes, and greater circuit layout densities.
VF(TRAN) = Pass transistor forward voltage drop
Rectifier Diodes
Any general-purpose rectifier diode can be used
with the AAT3680 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(DIODE) = Blocking diode forward voltage
PCB Layout
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 constantcurrent 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):
For the best results, it is recommended to physically place the battery pack as closely as possible to
the AAT3680's BAT pin. To minimize voltage drops
in the PCB, keep the high current carrying traces
adequately wide. For maximum power dissipation
in the pass transistor, it is critical to provide enough
copper to spread the heat. Refer to the AAT3680
demo board PCB layout in Figures 8, 9, and 10.
First, determine the minimum diode forward voltage
drop requirement. Refer to the following equation:
VIN(MIN) = VBAT(MAX) + VF(TRAN) + VF(DIODE)
Where:
VIN(MIN)
= Minimum input supply level
VBAT(MAX) = Maximum
required
battery
PD(MIN) =
14
charge
voltage
VF
ICC
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Evaluation Board Schematic
Figure 8: AAT3680 Demo Board Silk Screen /
Assembly Drawing.
Figure 9: AAT3680 Demo Board Component
Side Layout.
Figure 10: AAT3680 Demo Board
Solder Side Layout.
3680.2006.03.1.6
15
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Evaluation Board Bill of Materials
PNP Transistor Example
Designator
R3
R2
RT1
RT2
R1
C2
Header/SW1
C1
C3
R4
U1
D1
D2
D3
Q1
Part Type
0.2Ω, 0.5 Watt
1kΩ, 5%
100kΩ, 5%
100kΩ, 5%
3.9kΩ, 5%
1µF
Footprint
1206
1206
0805
0805
0805
1206
2mm, 3 Pos
10µF
10µF
Not Populated
Li-Ion Charge Controller IC
Green LED
1.0A Schottky Diode
0.0Ω Jumper
PNP Transistor
Manufacturer
Part Number
IRC
Various
Various
Various
Various
MuRata
LRC1206-01-R200F
Sullins
1206
1206
MuRata
MuRata
PRPN031PAEN
Select with Starting Jumper
GRM42-6X5R75K10
GRM42-6X5R106K16
MSOP-8
1206
SMA
AnalogicTech
Various
Diodes Inc.
AAT3680IKS-4.2-T1
SOT223
Zetex
F2T968
B340LA
P-Channel Power MOSFET Example
Designator
Part Type
Footprint
R3
R2
RT1
RT2
R1
C2
0.2Ω, 0.5W
1kΩ, 5%
100kΩ, 5%
100kΩ, 5%
1kΩ, 5%
1µF
1206
1206
0805
0805
0805
1206
Header/SW1
2mm, 3 Pos
C1
C3
R4
U1
D1
D2
D3
Q1
16
10µF
10µF
100kΩ, 5%
Li-Ion Charge Controller IC
Green LED
0.0Ω Jumper
1.0A Schottky Diode
30V P-Ch MOSFET, 0.2Ω
Manufacturer
Part Number
IRC
Various
Various
Various
Various
MuRata
LRC1206-01-R200F
Sullins
1206
1206
0805
MSOP-8
1206
MuRata
MuRata
Various
AnalogicTech
Various
SMA
TO-252
Diodes Inc.
Various
PRPN031PAEN
Select with Starting Jumper
GRM42-6X5R75K10
GRM42-6X5R106K16
AAT3680IKS-4.2
B340LA
RFD10P03L
3680.2006.03.1.6
AAT3680
Lithium-Ion/Polymer
Linear Battery Charge Controller
Ordering Information
Output Voltage
Package
Marking1
Part Number (Tape and Reel)2
MSOP-8
4.2V
ESXYY
AAT3680IKS-4.2-T1
TSOPJW-12
4.2V
ESXYY
AAT3680ITP-4.2-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
MSOP-8
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
0.30 ± 0.08
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on all part numbers listed in BOLD.
3680.2006.03.1.6
17
AAT3680
Lithium-Ion/Polymer
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
0.04 REF
0.055 ± 0.045
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
All dimensions in millimeters.
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights,
or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold
subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
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Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
18
3680.2006.03.1.6