AIC1821 AIC [Analog Intergrations Corporation], AIC1821 Datasheet - Page 5

• Manufacturer Part Number: AIC1821
• Description: ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
• Manufacturer: AIC [Analog Intergrations Corporation]

n
l THE OPERATION
ANALOG INTEGRATIONS CORPORATION
4F, 9 Industry E. 9th Road, Science-based Industrial Park , Hsinchu, Taiwan, R.O.C.
APPLICATION INFORMATIONS
Overcharge Protection
When the voltage of the battery cell exceeds the
overcharge protection voltage (V
overcharge delay time (T
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
2. The voltage of the battery cell falls below the
When the battery voltage is above V
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
overdischarge delay time (T
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
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
delay time (T
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
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
than the overcharge release voltage (V
V
overcharge protection voltage (V
is connected.
OCP
- V
HYS
OI
) through self-discharge.
) period, the overcurrent protection
ODR
) through charging.
OIP
) beyond the overcurrent
OI1
OC
and T
OD
) period, charging is
) period, discharging
OI2
OCP
ODP
OCP
) corresponding
) beyond the
) beyond the
) and a load
OCP
OCR
, the
ONE-CELL LITHIUM-ION BATTERY PROTECTION IC
or
l DESIGN GUIDE
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
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
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
Selection of External Control MOSFETs
Because the overcurrent protection voltage is
preset,
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
the overcurrent threshold current). For example, if
the overcurrent threshold current I
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
increases as the voltage between gate and source
decreases). Once the turn-on resistance of the
external
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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well.
the
LD
MOSFET
(Turn-on
).
threshold
FAX:[phone]
resistance
changes,
SPEC NO: DS-1821-P1 06/07/00
current
CC
ON
=2.3V). At the same
=V
AIC1821
the
of
T
for
OIP
is designed to
/ (2 x I
a
overcurrent
overcurrent
MOSFET
CH
T
) (I
).
5
T
is