S-8211D Datasheet, PDF (15/36 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 1-CELL PACK

Rev.4.5_00
BATTERY PROTECTION IC FOR 1-CELL PACK
S-8211D Series
„ Operation
Remark Refer to the “Battery Protection IC Connection Example”.
1. Normal Status
This IC monitors the voltage of the battery connected between the VDD pin and VSS pin and the voltage difference
between the VM pin and VSS pin to control charging and discharging. When the battery voltage is in the range from
overdischarge detection voltage (V_DL) to overcharge detection voltage (V_CU), and the VM pin voltage is not more than
the discharge overcurrent detection voltage (V_DIOV), the IC turns both the charging and discharging control FETs on.
This condition is called the normal status, and in this condition charging and discharging can be carried out freely.
The resistance (R_VMD) between the VM pin and VDD pin, and the resistance (R_VMS) between the VM pin and VSS pin
are not connected in the normal status.
Caution When the battery is connected for the first time, discharging may not be enabled. In this case, short
the VM pin and VSS pin or connect the charger to restore the normal status.
2. Overcharge Status
When the battery voltage becomes higher than overcharge detection voltage (V_CU) during charging in the normal
status and detection continues for the overcharge detection delay time (t_CU) or longer, the S-8211D Series turns the
charging control FET off to stop charging. This condition is called the overcharge status.
The resistance (R_VMD) between the VM pin and VDD pin, and the resistance (R_VMS) between the VM pin and VSS pin
are not connected in the overcharge status.
The overcharge status is released in the following two cases ( (1) and (2) ).
(1) In the case that the VM pin voltage is higher than or equal to charger detection voltage (V_CHA), and is lower than
the discharge overcurrent detection voltage (V_DIOV), S-8211D Series releases the overcharge status when the
battery voltage falls below the overcharge release voltage (V_CL).
(2) In the case that the VM pin voltage is higher than or equal to the discharge overcurrent detection voltage (V_DIOV),
S-8211D Series releases the overcharge status when the battery voltage falls below the overcharge detection
voltage (V_CU).
When the discharge is started by connecting a load after the overcharge detection, the VM pin voltage rises more
than the voltage at VSS pin due to the V_f voltage of the parasitic diode. This is because the discharge current
flows through the parasitic diode in the charging control FET. If this VM pin voltage is higher than or equal to the
discharge overcurrent detection voltage (V_DIOV), S-8211D Series releases the overcharge status when the battery
voltage is lower than or equal to the overcharge detection voltage (V_CU).
Cautions 1. If the battery is charged to a voltage higher than overcharge detection voltage (V_CU) and the
battery voltage does not fall below overcharge detection voltage (V_CU) even when a heavy load is
connected, discharge overcurrent detection and load short-circuiting detection do not function
until the battery voltage falls below overcharge detection voltage (V_CU). Since an actual battery
has an internal impedance of tens of mΩ, the battery voltage drops immediately after a heavy
load that causes overcurrent is connected, and discharge overcurrent detection and load short-
circuiting detection function.
2. When a charger is connected after overcharge detection, the overcharge status is not released
even if the battery voltage is below overcharge release voltage (V_CL). The overcharge status is
released when the VM pin voltage goes over charger detection voltage (V_CHA) by removing the
charger.
Seiko Instruments Inc.
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