S-8232 Datasheet, PDF (14/27 Pages) Seiko Instruments Inc – BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK

BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK
S-8232 Series
Rev.5.4_00
Delay Circuit
The overcharge detection delay time (t_{CU1, 2}), the overdischarge detection delay time (t_{DD1, 2}), and the
overcurrent detection delay time 1 (t_I0V1) change with an external capacitor (C3). Since one capacitor
determine each delay time, delay times are correlated by the following ratio :
Overcharge delay time : Overdischarge delay time : Overcurrent delay time = 100 : 10 : 1
The delay times are calculated by the following equations : (Ta = − 40 to + 85 °C)
Min., Typ., Max.
Overcharge detection delay time t_CU [s] = Delay factor ( 2.500, 4.545, 9.364 ) × C3 [µF]
Overdischarge detection delay time t_DD [s] = Delay factor ( 0.3045, 0.4545, 0.6409 ) × C3 [µF]
Overcurrent detection delay time t_IOV1 [s] = Delay factor ( 0.02864, 0.04545, 0.06682 ) × C3 [µF]
Remark The delay time for overcurrent detection 2 is fixed by an internal circuit. The delay time cannot
be changed via an external capacitor.
0 V Battery Charging Function ^*3
This function is used to recharge both of two serially-connected batteries after they self-discharge to 0 V.
When the 0 V charging start voltage (V_0CHA) or higher is applied to between VM and VCC by connecting
the charger, the charging FET gate is fixed to V_CC potential.
When the voltage between the gate and the source of the charging FET becomes equal to or higher than
the turn-on voltage by the charger voltage, the charging FET turns on to start charging. At this time, the
discharging FET turns off and the charging current flows through the internal parasitic diode in the
discharging FET. If all the battery voltages become equal to or higher than the overdischarge release
voltage (V_{DU1, 2}), the normal condition returns.
0 V Battery Charge Inhibiting Function ^*3
This function is used for inhibiting charging when either of the connected batteries goes 0 V due to its
self-discharge. When the voltage of either of the connected batteries goes below 0 V charge inhibit
voltage 1 and 2 (V_{0INH1, 2}), the charging FET gate is fixed to "EB−" to inhibit charging. Charging is
possible only when the voltage of both connected batteries goes 0 V charge inhibit voltage 1 and 2
(V_{0INH1, 2}) or more.
Note that charging may be possible when the total voltage of both connected batteries is less than the
minimum value (V_DSOPmin) of the operating voltage between VCC and VSS even if the voltage of either of
the connected batteries is 0 V charge inhibit voltage 1 and 2 (V_{0INH1, 2}) or less. Charging is prohibited
when the total voltage of both connected batteries reaches the minimum value (V_DSOPmin) of the operating
voltage between VCC and VSS.
When using this optional function, a resistor of 4.7 MΩ is needed between the gate and the source of the
charging control FET (refer to the Figure 8).
*1. When initially connecting batteries, the IC may fail to enter the normal condition (discharging ready
state). If so, once set the VM pin to VSS voltage (short pins VM and VSS or connect a charger).
*2. The products indicated with *4 of the 2. Product Name List in the “„ Product Name Structure” are set
to “overcharge detection / release hysteresis”, “no final overcharge function”, and “0 V battery charge
inhibiting function.” The following phenomena may be found, but there is no problem for practical use.
The product is an overcurrent condition due to overload connection when the battery voltage is
overcharge release voltage (V_{CD1, 2}) or more and overcharge detection voltage (V_{CU1, 2}) or less. Usually,
the IC returns to its normal condition when overload is removed under this condition. However, the
charging FET may be turned OFF when overload is removed under this condition, leading to an
overcharge condition. If so, attach load to start discharge. The charging FET is turned ON to return to
the normal condition. Refer to the “Overcharge condition” in this section.
*3. Some lithium ion batteries are not recommended to be recharged after having been completely
discharged. Please contact the battery manufacturer when you decide to select a 0 V battery charging
function.
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Seiko Instruments Inc.