AIC1811
One-Cell Lithium-Ion Battery Protection IC
DS-1811-00 June 7, 00
www.analog.com.tw
1
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FEATURES
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Reduction in Board Size due to Miniature
Package SOT-23-5 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
50mV for the AIC1811A
4.30V
50mV for the AIC1811B
4.25V
50mV for the AIC1811C
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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 AIC1811 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 AIC1811 into the limited space of
battery pack.
The accurate
50mV 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+
51K
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
AIC1811
Protection Circuit for One-Cell Lithium-Ion Battery
AIC1811
2
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ORDERING INFORMATION
PACKAGE TYPE
V: SOT-23-5
OVERCHARGE PROTECTION
A: 4.35V
B: 4.30V
C: 4.25V
ORDER NUMBER
PIN CONFIGURATION
AIC1811ACV
AIC1811BCV
AIC1811CCV
(SOT-23-5)
TOP VIEW
VCC
OD
GND
CS
OC
AIC1811 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
O C
R3
10M
V
O D
V
CC
V
CS
R2
5
4
3
2
1
C1
0.1
F
R1
100
OC
CS
OD
GND
VCC
AIC1811
AIC1811
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
AIC1811A
4.30
4.35
4.40
AIC1811B
4.25
4.30
4.35
Overcharge Protection Voltage
AIC1811C
V
OCP
4.20
4.25
4.30
V
Overcharge Hysteresis Voltage
V
HYS
150
200
250
mV
Overdischarge Protection
Voltage
V
ODP
2.2
2.4
2.6
V
Overdischarge Release Voltage
V
ODR
2.6
2.9
3.2
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
50
100
150
mS
Overdischarge Delay Time
V
CC
= 2.5V
2.3V
T
OD
50
100
150
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
150
300
450
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
AIC1811
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.
AIC1811
5
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APPLICATION INFORMATIONS
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 AIC1811 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 AIC1811 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 AIC1811 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 AIC1811
immediately turns on all the timing generation and
AIC1811
6
detection circuitry. Charging is determined to be in
progress if the voltage between CS and GND is
below charge detection threshold voltage (V
CH
).
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
connected under overdischarge condition and
overstress protection at reverse connecting of a
charger. Larger value of R2 reduces the charger
leakage current in overcharge mode, but possibly
disables the charge detection function after
overdischarge. Resistance of
51K
is
recommended.
AIC1811
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TIMING DIAGRAM
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Overcharge
and
Overdischarge
Protection
charger connected
load connected
load connected
charger connected
charger connected
Hi-Z
TOD
TOC
TOC
V
CC
V
OC
V
OD
0V
V
CC
V
CC
V
ODR
V
ODP
V
OCP
V
OCP
-V
HYS
Hi-Z
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Overcurrent Protection (V
CC
=3.5V)
V
CC
V
CC
0.2V
V
OD
V
BATT-
0V
0V
1V
V
CC
<T
OI1
T
OI2
V
OC
T
OI1
AIC1811
8
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PHYSICAL DIMENSIONS
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SOT-25 (unit: mm)
SYMBOL
MIN
MAX
A
1.00
1.30
A1
--
0.10
A2
0.70
0.90
b
0.35
0.50
C
0.10
0.25
D
2.70
3.10
E
1.40
1.80
e
1.90 (TYP)
H
2.60
3.00
L
0.37
--
E
e
D
H
A1
A
A2
b
L
1
C
1
1
9
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SOT-23-5 MARKING
Part No.
Marking
AIC1811ACV
EA0A
AIC1811BCV
EA0B
AIC1811CCV
EA0C
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