S-8240BAA-I6T1U Datasheet, PDF (13/37 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 1-CELL PACK

Rev.1.0_00
BATTERY PROTECTION IC FOR 1-CELL PACK
S-8240B Series
 Operation
Remark 1. Refer to " Battery Protection IC Connection Example".
2. Unless otherwise specified, the VM pin voltage is based on V_SS.
1. Normal status
The S-8240B Series monitors the voltage of the battery connected between VDD pin and VSS pin, the voltage between
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 charge
overcurrent detection voltage (V_CIOV) to discharge overcurrent detection voltage (V_DIOV), the S-8240B 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 VDD pin and VM pin (R_VMD), and the resistance between VM pin and VSS pin (R_VMS) are not
connected in the normal status.
Caution After the battery is connected, discharging may not be carried out. In this case, the S-8240B Series
becomes the normal status by connecting a charger.
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 the condition continues
for the overcharge detection delay time (t_CU) or longer, the S-8240B 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-8240B 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-8240B 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-8240B 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 the condition continues
for the overcharge detection delay time (t_CU) or longer, the S-8240B 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 equal to or higher than 0 V typ., the S-8240B 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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