BATTERY PROTECTION IC FOR 2-SERIAL-CELL PACK

S-8232 Series

Seiko Instruments Inc.

14

Delay Circuit

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.

= Delay factor

( 2.500,

4.545,

9.364 )

× C3 [µF]

= Delay factor ( 0.3045, 0.4545, 0.6409 ) × C3 [µF]

= 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 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

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

−" to inhibit charging. Charging is

possible only when the voltage of both connected batteries goes 0 V charge inhibit voltage 1 and 2

Note that charging may be possible when the total voltage of both connected batteries is less than the

voltage between VCC and VSS.

When using this optional function, a resistor of 4.7 M

Ω 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

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.