AiT Semiconductor Inc.
A4002
www.ait-ic.com
BATTERY MANAGEMENT
ONE CELL LITHIUM-ION/POLYMER BATTERY PROTECTION IC
however, an internal impedance of several dozens of mΩ, and the battery voltage drops immediately
after a heavy load which causes an overcurrent is connected, the overcurrent 1 and overcurrent 2
work. Detection of load short-circuiting works regardless of the battery voltage.
Overdischarge Condition
When the battery voltage drops below the overdischarge detection voltage (VDL) during discharging under
normal condition and it continues for the overdischarge detection delay time (tDL) or longer, the A4002 turns
the discharging condition. After the dischargingcontrol FET is turned off, the VM pin is pulled up by the RVMD
resistor between VM and VDD in A4002. meanwhile when VM is bigger than 1.5V (typ.) (the load
short-circuiting detection voltage), the current of the chip reduced to the power-down current (IPDN). This
condition is called power-down condition. The VM and VDD pins are shorted by the RVMD resistor in the IC
under the overdischarge and power-down conditions. The power-down condition is released when a charger
is connected and the potential difference between VM and VDD becomes 1.3V (typ.) or higher (load
short-circuiting detection voltage). At this time, the FET is still off. When the battery voltage becomes the
overdischarge detection voltage (VDL) or higher (see note), the A4002 turns the FET on and changes to the
normal condition from the overdischarge condition.
Remark If the VM pin voltage is no less than the charger detection voltage (VCHA), the battery under
overdischarge condition is connected to a charger, the overdischarge condition is released(the
discharging control FET is turned on) as usual, provided that the battery voltage reaches the
overdischarge release voltage (VDU) or higher.
Overcurrent Condition
When the discharging current becomes equal to or higher than a specified value (the VM pin voltage is equal
to or higher than the overcurrent detection voltage) during discharging under normal condition and the state
continues for the overcurrent detection delay time or longer, the A4002 turns off the discharging control FET
to stop discharging. This condition is called overcurrent condition. (The overcurrent includes overcurrent or
load short-circuiting). The VM and GND pins are shorted internally by the RVMS resistor under the overcurrent
condition. When a load is connected, the VM pin voltage equals the VDD voltage due to the load. The
overcurrent condition returns to the normal condition when the load is released and the impedance between
the B+ and B-pins becomes higher than the automatic recoverable impedance. When the load is removed,
the VM pin goes back to the GND potential since the VM pin potential is lower than the overcurrent detection
voltage (VIOV1),the IC returns to the normal condition.
Abnormal Charge Current Detection
If the VM pin voltage drops below the charger detection voltage (VCHA) during charging under the normal
condition and it continues for the overcharge detection delay time (tCU) or longer, the A4002 turns the charging
control FET off and stops charging. This action is called abnormal charge current detection. Abnormal charge
current detection works when the discharging control FET is on and the VM pin voltage droops below the
REV1.0
- JUN 2018 RELEASED -
- 6 -
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