S8240B datasheet(13/37 Pages) SII

13 / 37 page

BATTERY PROTECTION IC FOR 1-CELL PACK

Rev.1.0_00

S-8240B Series



Operation

Remark 1. Refer to " Battery Protection IC Connection Example".

2. Unless otherwise specified, the VM pin voltage is based on VSS.

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 (VDL) to overcharge detection voltage (VCU), and the VM pin voltage is in the range from charge

overcurrent detection voltage (VCIOV) to discharge overcurrent detection voltage (VDIOV), 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 (RVMD), and the resistance between VM pin and VSS pin (RVMS) 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 VCL

≠ VCU (Product in which overcharge release voltage differs from overcharge detection voltage)

When the battery voltage becomes higher than VCU during charging in the normal status and the condition continues

for the overcharge detection delay time (tCU) 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 VDIOV, the S-8240B Series releases the overcharge status when

the battery voltage falls below overcharge release voltage (VCL).

(2) In the case that the VM pin voltage is equal to or higher than VDIOV, the S-8240B Series releases the overcharge

status when the battery voltage falls below VCU.

When the discharge is started by connecting a load after the overcharge detection, the VM pin voltage rises by the Vf

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 VDIOV, the S-8240B Series releases

the overcharge status when the battery voltage is equal to or lower than VCU.

Caution If the battery is charged to a voltage higher than VCU and the battery voltage does not fall below VCU

even when a heavy load is connected, discharge overcurrent detection and load short-circuiting

detection do not function until the battery voltage falls below VCU. Since an actual battery has an

internal impedance of tens of m

Ω, 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 VCL = VCU (Product in which overcharge release voltage is the same as overcharge detection voltage)

When the battery voltage becomes higher than VCU during charging in the normal status and the condition continues

for the overcharge detection delay time (tCU) 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 VCU.

Caution 1. If the battery is charged to a voltage higher than VCU and the battery voltage does not fall below VCU

even when a heavy load is connected, discharge overcurrent detection and load short-circuiting

detection do not function until the battery voltage falls below VCU. Since an actual battery has an

internal impedance of tens of m

Ω, 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 VCL. The overcharge status is released when the VM pin voltage goes

over 0 V typ. by removing the charger.

S8240B Datasheet(PDF) 13 Page - Seiko Instruments Inc

S8240B Datasheet(HTML) 13 Page - Seiko Instruments Inc

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