BATTERY PROTECTION IC FOR 1-CELL PACK
S-8241 Series
Rev.7.6_00
4. Overdischarge Condition
With power-down function
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 S-8241 turns the discharging
control FET off and stops discharging. This condition is called overdischarge condition. After the discharging control
FET is turned off, the VM pin is pulled up by the RVMD resistor between VM and VDD in the IC. Meanwhile the potential
difference between VM and VDD drops below 1.3 V (typ.) (the load short-circuiting detection voltage), current
consumption of the IC is reduced to the power-down current consumption (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 1.3 V (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*1, the S-8241 turns the FET on and changes to the
normal condition from the overdischarge condition.
*1. If the VM pin voltage is no less than the charger detection voltage (VCHA), when 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.
Without power-down function
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 S-8241 turns the discharging
control FET off and stops discharging. When the discharging control FET is turned off, the VM pin is pulled up by the
RVMD resistor between VM and VDD in the IC. Meanwhile the potential difference between VM and VDD drops below 1.3
V (typ.) (the load short-circuiting detection voltage), current consumption of the IC is reduced to the overdischarge
current consumption (IOPED). This condition is called overdischarge condition. The VM and VDD pins are shorted by the
RVMD resistor in the IC under the overdischarge condition.
When a charger is connected, the overdischarge condition is released in the same way as explained above in respect to
products having the power-down function. For products without the power-down function, in addition, even if the charger
is not connected, the S-8241 turns the discharging control FET on and changes to the normal condition from the
overdischarge condition provided that the load is disconnected and that the potential difference between VM and VSS
drops below the overcurrent 1 detection voltage (VIOV1), since the VM pin is pulled down by the RVMS resistor between
VM and VSS in the IC when the battery voltage reaches the overdischarge release voltage (VDU) or higher.
5. Charger Detection
If the VM pin voltage is lower than the charger detection voltage (VCHA) when a battery in overdischarge condition is
connected to a charger, overdischarge hysteresis is released, and when the battery voltage becomes equal to or higher
than the overdischarge detection voltage (VDL), the overdischarge condition is released (the discharging control FET is
turned on). This action is called charger detection. (The charger detection reduces the time for charging in which
charging current flows through the internal parasitic diode in the discharging control FET) .
If the VM pin voltage is not lower than the charger detection voltage (VCHA) when a battery in overdischarge condition is
connected to a charger, the overdischarge condition is released (the discharging control FET is turned on) as usual,
when the battery voltage reaches the overdischarge release voltage (VDU) or higher.
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Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
