S-8242B Datasheet, PDF (10/30 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK

BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK
S-8242B Series
Rev.1.4_00
„ Operation
Remark Refer to “„ Battery Protection IC Connection Example”.
1. Normal Status
This IC monitors the voltage of the battery connected between the VDD and VSS pins and the voltage difference
between the VM and VSS pins to control charging and discharging. When the battery voltage is in the range from
overdischarge detection voltage n (V_DLn) to overcharge detection voltage n (V_CUn), and the VM pin voltage is in the
range from the charger detection voltage (V_CHA) to overcurrent detection voltage 1 (V_IOV1), the IC 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.
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 connect the charger to restore the normal status.
2. Overcharge Status
When the battery voltage becomes higher than overcharge detection voltage n (V_CUn) during charging in the normal
status and detection continues for the overcharge detection delay time (t_CU) or longer, the S-8242B Series turns the
charging control FET off to stop charging. This condition is called the overcharge status.
The overcharge status is released in the following two cases ((1) and (2)).
(1) When the battery voltage falls below overcharge release voltage n (V_CLn), the S-8242B Series turns the charging
control FET on and returns to the normal status.
(2) When a load is connected and discharging starts, the S-8242B Series turns the charging control FET on and
returns to the normal status. Just after the load is connected and discharging starts, the discharging current
flows through the parasitic diode in the charging control FET. At this moment the VM pin potential becomes V_f,
the voltage for the parasitic diode, higher than the V_SS level. When the battery voltage goes under overcharge
detection voltage n (V_CUn) and provided that the VM pin voltage is higher than overcurrent detection voltage 1,
the S-8242B Series releases the overcharge condition.
Caution 1. If the battery is charged to a voltage higher than overcharge detection voltage n (V_CUn) and the
battery voltage does not fall below overcharge detection voltage n (V_CUn) even when a heavy
load is connected, overcurrent 1 and overcurrent 2 do not function until the battery voltage falls
below overcharge detection voltage n (V_CUn). 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 overcurrent 1 and overcurrent 2 function.
2. When a charger is connected after overcharge detection, the overcharge status is not released
even if the battery voltage is below overcharge release voltage n (V_CLn). The overcharge status
is released when the VM pin voltage goes over the charger detection voltage (V_CHA) by removing
the charger.
10
Seiko Instruments Inc.