PRELIMINARY
AIC1821
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
SPEC NO: DS-1821-P1 06/07/00
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500
FAX:(8863)577-2510
1
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FEATURES
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Reduction in Board Size due to Miniature Package
SOT-25 and Less External Components.
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Ultra-Low Quiescent Current at 7
A (V
CC
=3.5V).
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Ultra-Low Power-Down Current at 0.4
A (V
CC
=2.3V).
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Precision Overcharge Protection Voltage
4.35V
30mV for the AIC1821A
4.30V
30mV for the AIC1821B
4.25V
30mV for the AIC1821C
4.20V
30mV for the AIC1821D
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Built-in Delay Time Circuits for Overcharge, Over-
discharge, and Overcurrent Protection.
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Load Detection Function during Overcharge Mode.
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Two Detection Levels for Overcurrent Protection.
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APPLICATIONS
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Protection IC for One-Cell Lithium-Ion Battery
Pack.
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DESCRIPTION
The AIC1821 battery protection IC is designed to
protect lithium-ion battery from damage or
degrading the lifetime due to overcharge,
overdischarge, and/or overcurrent for one-cell
lithium-ion battery powered systems, such as
cellular phones. The ultra-small package and less
required external components make it ideal to
integrate the AIC1821 into the limited space of
battery pack.
The accurate
30mV overcharging detection
voltage ensures safe and full utilization charging.
Three different specification values for overcharge
protection voltage are provided for various
protection requirements. The very low standby
current drains little current from the cell while in
storage.
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TYPICAL APPLICATION CIRCUIT
BATT-
BATT+
100K
5
4
3
2
1
R2
R3
FUSE
C1
0.1
F
R1
100
10M
M2 SI9926
M1
SI9926
BATTERY
OC
CS
OD
GND
VCC
AIC1821
Protection Circuit for One-Cell Lithium-Ion Battery
AIC1821
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
SPEC NO: DS-1821-P1 06/07/00
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500
FAX:(8863)577-2510
2
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ORDERING INFORMATION
PACKAGE TYPE
V: SOT-23-5
OVERCHARGE PROTECTION
A: 4.35V
B: 4.30V
C: 4.25V
D: 4.20V
ORDER NUMBER
PIN CONFIGURATION
AIC1821ACV
AIC1821BCV
AIC1821CCV
AIC1821DCV
(SOT-23-5)
TOP VIEW
VCC
OD
GND
CS
OC
AIC1821 XCX
3
2
1
4
5
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ABSOLUTE MAXIMUM RATINGS
Supply Voltage
.................................... ... ... ... ... ... .....................................................
18V
DC Voltage Applied on other Pins ............... ... ... ... ... ... ... ... ... ... ... .............................. 18V
Operating Temperature Range ..................................... ... ... ... ... ... ... . ............. -40
C~85
C
Storage Temperature Range ......................... ... ... ... ... ... ... ... ..................... - 65
C~125
C
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TEST CIRCUIT
51K
I
OC
I
CC
S1
V
OC
R3
10M
V
OD
V
CC
V
CS
R2
5
4
3
2
1
C1
0.1
F
R1
100
OC
CS
OD
GND
VCC
AIC1821
AIC1821
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
SPEC NO: DS-1821-P1 06/07/00
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500
FAX:(8863)577-2510
3
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ELECTRICAL CHARACTERISTICS
(Ta=25
C, unless otherwise specified.)
PARAMETER
TEST CONDITIONS
SYMBOL
MIN.
TYP.
MAX.
UNIT
Supply Current
V
CC
=3.5V
I
CC
7
11
A
Power-Down Current
V
CC
=2.3V,
I
PD
0.4
1.0
A
AIC1821A
4.32
4.35
4.38
AIC1821B
4.27
4.30
4.33
AIC1821C
4.22
4.25
4.28
V
Overcharge Protection Voltage
AIC1821D
V
OCP
4.17
4.20
4.23
Overcharge Hysteresis Voltage
V
HYS
230
300
370
mV
Overdischarge Protection
Voltage
V
ODP
2.45
2.6
2.75
V
Overdischarge Release Voltage
V
ODR
2.85
3.0
3.15
V
Overcurrent Protection Voltage
V
CC
=3.5V
V
OIP
180
200
220
mV
Overcharge Delay Time
V
CC
=V
OCP
-0.1
V
OCP
+ 0.1V
T
OC
250
500
750
mS
Overdischarge Delay Time
V
CC
= 2.5V
2.3V
T
OD
5
10
15
mS
Overcurrent Delay Time (1)
V
CC
=3.5V, 1V>V
CS
>0.2V
T
OI1
5
10
15
mS
Overcurrent Delay Time (2)
V
CC
=3.5V, V
CS
>1V
T
OI2
50
S
OC Pin Source Current
V
CC
=3.5V, OC pin short to
GND
I
OC
240
340
440
A
OD Pin Output "H" Voltage
V
DH
V
CC
-0.1 V
CC
-0.02
V
OD Pin Output "L" Voltage
V
DL
0.01
0.1
V
Load Dectection Threshold
Voltage
V
CC
=V
OCP
50mV
V
LD
0.3
0.4
V
Charge Detection Threshold
Voltage
V
CC
=2.3V
V
CH
-0.45
-0.3
V
AIC1821
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
SPEC NO: DS-1821-P1 06/07/00
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500
FAX:(8863)577-2510
4
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BLOCK DIAGRAM
Power-down
Control
Wake-up Control
-0.3V
3
4
1
2
5
VCC
Overdischarge
Delay Circuit
Overcharge
Delay Circuit
Overcurrent
Delay Circuit
Enable
Enable
Load Detected
0.3V
0.2V
CS
GND
OC
OD
1.2V
1V
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PIN DESCRIPTIONS
PIN 1: OC
- PMOS open drain output for control
of the charge control MOSFET M2. In
normal mode, this PMOS turns on to
pull the gate of the MOSFET M2 to
high, then the MOSFET M2 turns on.
When overcharge occurs, this PMOS
turns off, then no current flows
through R3 and the MOSFET M2
turns off.
PIN 2: GND - Ground pin. This pin is to be
connected to the negative terminal of
the battery cell.
PIN 3: OD
- Output pin for control of the
discharge control MOSFET M1.
When overdischarge occurs, this pin
goes low to turn off the MOSFET M1
and discharging is inhibited.
PIN 4: CS
- Input pin for current sensing. Using
the sum of drain-source voltages of
the MOSFET M1 and the MOSFET
M2 (voltage between CS and GND),
it senses discharge current during
normal mode and detects whether
charge current is present during
power-down mode. It also used to
detect whether load is connected
during overcharge mode.
PIN 5: VCC - Power supply pin. This pin is to be
connected to the positive terminal of
the battery cell.
AIC1821
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
SPEC NO: DS-1821-P1 06/07/00
ANALOG INTEGRATIONS CORPORATION
www.analog.com.tw
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
TEL: (8863)577-2500
FAX:(8863)577-2510
5
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APPLICATION INFORMATIONS
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THE OPERATION
Overcharge Protection
When the voltage of the battery cell exceeds the
overcharge protection voltage (V
OCP
) beyond the
overcharge delay time (T
OC
) period, charging is
inhibited by the turning-off of the charge control
MOSFET M2. The overcharge delay time is fixed to
100mS by IC internal circuit. The overcharge
condition is released in two cases:
1. The voltage of the battery cell becomes lower
than the overcharge release voltage (V
OCR
or
V
OCP
- V
HYS
) through self-discharge.
2. The voltage of the battery cell falls below the
overcharge protection voltage (V
OCP
) and a load
is connected.
When the battery voltage is above V
OCP
, the
overcharge condition is never released even a load
is connected to the pack.
Overdischarge Protection
When the voltage of the battery cell goes below the
overdischarge protection voltage (V
ODP
) beyond the
overdischarge delay time (T
OD
) period, discharging
is inhibited by the turning-off of the discharge
control MOSFET M1. The overdischarge delay time
defaults to 100mS. Inhibition of discharging is
immediately released when the voltage of the
battery cell becomes higher than overdischarge
release voltage (V
ODR
) through charging.
Overcurrent Protection
In normal mode, the AIC1821 continuously monitors
the discharge current by sensing the voltage of CS
pin. If the voltage of CS pin exceeds the overcurrent
protection voltage (V
OIP
) beyond the overcurrent
delay time (T
OI
) period, the overcurrent protection
circuit operates and discharging is inhibited by the
turning-off of the discharge control MOSFET M1.
The overcurrent condition returns to the normal
mode when the load is released and the impedance
between the BATT+ and BATT- terminals is 20M
or higher.
The AIC1821 is provided with the two overcurrent
detection levels (0.2V and 1V) and the two
overcurrent delay time (T
OI1
and T
OI2
) corresponding
to each overcurrent detection level.
Load Detection after Overcharge
The load detection function after overcharge is
implemented by detecting the CS pin voltage. Once
a load is connected to the battery pack after
overcharge, discharge current flows through the
parasitic diode of MOSFET M2 and there is a diode
voltage drop between CS and GND. Load is
determined to be connected to the pack if the CS
pin voltage is above load detection threshold
voltage (V
LD
).
Power-Down after Overdischarge
When overdischarge occurs, the AIC1821 will go
into power-down mode, turning off all the timing
generation and detection circuitry to reduce the
quiescent current to 0.4
A (V
CC
=2.3V). At the same
time, the CS pin is pull-high to VCC through a high
resistance resistor.
Charge Detection after Overdischarge
When overdischarge occurs, the discharge control
MOSFET M1 turns off and discharging is inhibited.
However, charging is still permitted through the
parasitic diode of M1. Once the charger is
connected to the battery pack, the AIC1821
immediately turns on all the timing generation and
detection circuitry. Charging is determined to be in
progress if the voltage between CS and GND is
below charge detection threshold voltage (V
CH
).
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DESIGN GUIDE
Selection of External Control MOSFETs
Because the overcurrent protection voltage is
preset, the threshold current for overcurrent
detection is determined by the turn-on resistance of
the discharge control MOSFET M1. The turn-on
resistance of the external control MOSFETs can be
determined by the equation: R
ON
=V
OIP
/ (2 x I
T
) (I
T
is
the overcurrent threshold current). For example, if
the overcurrent threshold current I
T
is designed to
be 3A, the turn-on resistance of the external control
MOSFETs must be 33m
. Users should be aware
that turn-on resistance of the MOSFET changes
with temperature variation due to heat dissipation. It
changes with the voltage between gate and source
as well. (Turn-on resistance of a MOSFET
increases as the voltage between gate and source
decreases). Once the turn-on resistance of the
external MOSFET changes, the overcurrent
threshold current will change accordingly.
Suppressing the Ripple and Disturbance
from Charger
To suppress the ripple and disturbance from
charger, connecting R1, C1 to VCC pin is
recommended.
Protection at CS pin
R2 is used for latch-up protection when charger is
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