BQ77915: Exceed absolute maximum rating of LD in stacked arrangement

Martin R.

Part Number: BQ77915

Hello guys,

I came across something that made me wonder.

In a stacked arrangement of 2x bq77915 with low-sided mosfets, UV loafd detection, battery voltage of 42V (10s @ OV 4,2V) and a load like 2k resistor is connected.

Everytime any protection trips and one or both mosfets cut of, PACK- Pin get near PACK+ pin. Further I have 42V on LD Pin. The absolut maximum ratings says MAX 20V are allowed.

Do i have a fundamental understanding mistake? Probably someone can clarfy me.

Thanks in advice!

over 4 years ago

0 Martin R. over 4 years ago

Intellectual 335 points

0 Matt Sunna over 4 years ago in reply to Martin R.

TI__Guru* 81035 points

Hi Martin,

I understand your concern. The 20V Abs max is derived from the table below where the LD pin was tested by forcing current (to measure the clamp voltage) and by forcing a voltage (to test the max current).There is a clamp internal to this pin, so the current into this pin through the 450k will be very small with PACK- at 42V. This should be okay.

Best regards,

Matt

Power management

Power management forum

BQ77915: Exceed absolute maximum rating of LD in stacked arrangement