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SC451

LI-ION BATTERY PROTECTOR

Silan Microelectronics 

Silan

Semiconductors

SC451XX

• VD2/OVER-DISCHARGE DETECTOR

The VD2 monitors a VDD pin voltage. When the VDD voltage crosses the over-discharge detector threshold

VDET2 from a high value to a value lower than the VDET2, the VD2 can sense an over-discharging and the

external discharge control Nch-MOS-FET turns to “off” with the DOUT pin being at “L”.

Resetting the VD2 with the DOUT pin level being “H” again after detecting over-discharge is only possible by

connecting a charger to the battery pack. When the VDD voltage stays under over-discharge detector threshold

VDET2 charge current can flow through parasitic diode of external discharge control Nch-MOS-FET, then after the

VDD voltage comes up to a value larger than VDET2 discharging process would be advanced through “on” state

discharge control Nch-MOS-FET. Connecting a charger to the battery pack makes the DOUT level being “H”

instantaneously when the VDD voltage is higher than VDET2.

When a cell voltage equals to zero, connecting charger to the battery pack makes the system allowable for

charge with higher charge voltage than Vst, 1.2V Max.

An output delay time of the over-discharge detection is fixed internally. Though the VDD voltage would be

going down to a lower level than VDET2 if it is within a time period of the output delay time, VD2 would not output

a signal for turning “off” of discharge control Nch-MOS-FET.

After detection of an over-discharge by VD2, supply current would be reduced to 0.3µATYP. at VDD=2.0V

and into standby, only the charger detector is operating.

The output type of DOUT pin is CMOS having “H” level of VDD and “L” level of VSS.

• VD3/EXCESS CURRENT DETECTOR, SHORT CIRCUIT PROTECTOR

*Both of the excess current detector and short circuit protector can work when both control Nch-MOS-FETs

are in “on” state.

When the V-pin voltage is going up to a value between the short protection voltage Vshort and excess

current threshold VDET3, the excess current detector operates and further soaring of V-pin voltage higher than

Vshort makes the short circuit protector enabled. As a result the external discharge control Nch-MOS-FET turns

to “off” with the DOUT pin being at “L”.

*An output delay time for the excess current detector is internally fixed, 13ms TYP. at VDD=3.0V. A quick

recovery of V-pin level from a value between Vshort and VDET3 within the delay time keeps the discharge control

FET staying “ON” state.

When the short circuit protector is enabled, the DOUT would be “L” and its delay time would be 5µs TYP.

*The V-pin has a built-in pull down resistor, TYP.100KΩ, connected to the VSS pin.

After an excess current or short circuit protection is detected, removing a cause of excess current or external

short circuit makes an external discharge control Nch-MOS-FET to an “on” state automatically with the V-pin level

being down to the VSS level through the built-in pull down resistor.

* When VDD voltage is higher than VDET2 at a time when the excess current is detected the SC451XX does not

enter a standby mode, while VDD voltage is lower than VDET2 the SC451XX enters a standby mode.

After detecting short circuit the SC451XX will not enter a standby mode.

HANGZHOU SILAN MICROELECTRONICS JOINT-STOCK CO.,LTD

Rev: 1.0 2000.12.31

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