S-8240ACS-M6T1U Datasheet, PDF (17/45 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 1-CELL PACK

Rev.2.1_01
BATTERY PROTECTION IC FOR 1-CELL PACK
S-8240A 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-8240A 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-8240A
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-8240A 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-8240A 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-8240A 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-8240A 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-8240A
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-8240A 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-8240A 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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