S-8252AAA-M6T1U Datasheet, PDF (15/36 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC

Rev.3.2_00
BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK
S-8252 Series
 Operation
Remark Refer to the " Battery Protection IC Connection Example".
Caution Unless otherwise specified, the VM pin voltage is based on V_SS.
1. Normal status
1. 1 With charge overcurrent detection function
The S-8252 Series 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 in the range from the charge overcurrent detection voltage (V_CIOV) to discharge overcurrent
detection voltage (V_DIOV), The S-8252 Series 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 set the VM pin voltage at the level of V_CIOV or more and V_DIOV or
less by connecting the charger. The S-8252 Series then returns to the normal status.
1. 2 Without charge overcurrent detection function
The S-8252 Series 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 in the range from the charger detection voltage (V_CHA) to discharge overcurrent detection
voltage (V_DIOV), The S-8252 Series 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 set the VM pin voltage at the level of V_CHA or more and V_DIOV or
less by connecting the charger. The S-8252 Series then returns to the normal status.
2. Overcharge status
When the battery voltage becomes higher than V_CU during charging in the normal status and detection continues for
the overcharge detection delay time (t_CU) or longer, the S-8252 Series turns the charging control FET off to stop
charging. This condition is called the overcharge status.
R_VMD and R_VMS 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 lower than V_DIOV, the S-8252 Series releases the overcharge status when
the battery voltage falls below V_CL.
(2) In the case that the VM pin voltage is higher than or equal to V_DIOV, the S-8252 Series releases the overcharge
status when the battery voltage falls below 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, 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 V_DIOV, the
S-8252 Series releases the overcharge status when the battery voltage is lower than or equal to V_CU.
Caution 1. If the battery is charged to a voltage higher than V_CU and the battery voltage does not fall below
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 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. If a charger is connected after the overcharge detection, the overcharge status is not released
even when the battery voltage falls below V_CL. The S-8252 Series releases the overcharge status
when the VM pin voltage returns to V_CIOV (or V_CHA when without charge overcurrent detection
function) or higher by removing the charger.
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