S-8250BAB-I6T1U Datasheet, PDF (14/32 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 1-CELL PACK

BATTERY PROTECTION IC FOR 1-CELL PACK
S-8250B Series
Rev.1.1_02
 Operation
Remark Refer to " Battery Protection IC Connection Example".
1. Normal status
The S-8250B Series monitors the voltage of the battery connected between the VDD pin and VSS pin and the voltage
between the VM pin and VSS pin to control charging and discharging. When the battery voltage is in the range from
the overdischarge detection voltage (V_DL) to the overcharge detection voltage (V_CU), and the VM pin voltage is in the
range from the charge overcurrent detection voltage (V_CIOV) to the discharge overcurrent detection voltage (V_DIOV),
the S-8250B Series turns both the charge and discharge control FETs on. This condition is called the normal status,
and in this condition charging and discharging can be carried out freely.
The resistance between the VM pin and VDD pin (R_VMD) and the resistance between the VM pin and VSS pin (R_VMS)
are not connected in the normal status.
Caution When the battery is connected for the first time, the S-8250B Series may not be in the normal status.
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 at the level of V_DIOV or less by connecting the charger. The S-8250B Series then becomes the
normal status.
2. Overcharge status
2. 1 V_CL ≠ V_CU (Product in which overcharge release voltage differs from overcharge detection voltage)
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-8250B Series turns the charge control FET off to
stop charging. This condition is called the overcharge status.
The overcharge status is released in the following two cases.
(1) In the case that the VM pin voltage is lower than V_DIOV, the S-8250B Series releases the overcharge status
when the battery voltage falls below overcharge release voltage (V_CL).
(2) In the case that the VM pin voltage is equal to or higher than V_DIOV, the S-8250B 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 by
the V_f voltage of the parasitic diode than the VSS pin voltage, because the discharge current flows through the
parasitic diode in the charge control FET. If this VM pin voltage is equal to or higher than V_DIOV, the S-8250B
Series releases the overcharge status when the battery voltage is equal to or lower than V_CU.
Caution
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. 2 V_CL = V_CU (Product in which overcharge release voltage is the same as overcharge detection voltage)
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-8250B Series turns the charge control FET off to
stop charging. This condition is called the overcharge status.
In the case that the VM pin voltage is higher than 0 V typ., the S-8250B Series releases the overcharge status
when the battery voltage falls below 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. When a charger is connected after overcharge detection, the overcharge status is not released
even if the battery voltage is below V_CL. The overcharge status is released when the VM pin
voltage goes over 0 V typ. by removing the charger.
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