S-8241ABKMC-GBKT2G Datasheet, PDF (21/39 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 1-CELL PACK

Rev.9.1_00
BATTERY PROTECTION IC FOR 1-CELL PACK
S-8241 Series
4. Overdischarge Status
With power-down function
When the battery voltage drops below the overdischarge detection voltage (V_DL) during discharging under normal status
and it continues for the overdischarge detection delay time (t_DL) or longer, the S-8241 turns the discharging control FET
off and stops discharging. This status is called overdischarge status. After the discharging control FET is turned off, the
VM pin is pulled up by the R_VMD 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 (I_PDN). This status is called power-down status. The VM and VDD pins are
shorted by the R_VMD resistor in the IC under the overdischarge and power-down statuses.
The power-down status 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 (V_DL) or higher^*1, the S-8241 turns the FET on and changes to the
normal status from the overdischarge status.
*1. If the VM pin voltage is no less than the charger detection voltage (V_CHA), when the battery under overdischarge
status is connected to a charger, the overdischarge status is released (the discharging control FET is turned on) as
usual, provided that the battery voltage reaches the overdischarge release voltage (V_DU) or higher.
Without power-down function
When the battery voltage drops below the overdischarge detection voltage (V_DL) during discharging under normal status
and it continues for the overdischarge detection delay time (t_DL) 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 R_VMD 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 (I_OPED). This status is called overdischarge status. The VM and VDD pins are shorted by the R_VMD resistor
in the IC under the overdischarge status.
When a charger is connected, the overdischarge status 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 status from the
overdischarge status provided that the load is disconnected and that the potential difference between VM and VSS
drops below the overcurrent 1 detection voltage (V_IOV1), since the VM pin is pulled down by the R_VMS resistor between
VM and VSS in the IC when the battery voltage reaches the overdischarge release voltage (V_DU) or higher.
5. Charger Detection
If the VM pin voltage is lower than the charger detection voltage (V_CHA) when a battery in overdischarge status is
connected to a charger, overdischarge hysteresis is released, and when the battery voltage becomes equal to or higher
than the overdischarge detection voltage (V_DL), the overdischarge status 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 (V_CHA) when a battery in overdischarge status is
connected to a charger, the overdischarge status is released (the discharging control FET is turned on) as usual, when
the battery voltage reaches the overdischarge release voltage (V_DU) or higher.
Seiko Instruments Inc.
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