AIC1811
n
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.
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 20MΩ 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
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.
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 0.4µA (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
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
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
5
AIC [ ANALOG INTERGRATIONS CORPORATION ]
