BQ76940: BQ76940

GURURAJ TALEWAD

Intellectual 445 points

Part Number: BQ76940

Hello,

I have used bq76940 and I m getting 44V at REGSRC, how to reduce it.

over 4 years ago

0 Jessica LI over 4 years ago

TI__Prodigy 590 points

Hello Gururaj,

For the REGSRC design for BQ76940, the datasheet shows using FET referenced to the VC5X voltage as a source follower, this topology allowe REGSRC to operate approximately Vgsth of the FET below the VC5X voltage. And the AN SLUA749A http://www.ti.com/lit/an/slua749a/slua749a.pdf give detail description for REGSRC deisgn in section 9.

Thank you

0 GURURAJ TALEWAD over 4 years ago in reply to Jessica LI

Intellectual 445 points

hello Jesica,

I have tried all configurations from datasheets. still, REGSRC voltage is 44V.

check image attached.

0 GURURAJ TALEWAD over 4 years ago in reply to Jessica LI

Intellectual 445 points

0 GURURAJ TALEWAD over 4 years ago in reply to GURURAJ TALEWAD

Intellectual 445 points

I tried both above circuits but still, voltage is 44V.

0 WM5295 over 4 years ago in reply to GURURAJ TALEWAD

TI__Guru 54715 points

Hi Gururaj,

If the REGSRC is 44V the FET is likely damaged or connected wrong.

Check the voltage of all the pins of the FET. If they are shorted together the FET is bad. Check if the source and drain could be swapped, if so is a diode drop through the FET.

Check the VC5X voltage and the gate voltage in the circuits above. There should be no current in the gate so the voltages should be the same. If there is a voltage difference the FET is damaged or there is an unexpected connection.

The source of the FET should be about 2V lower than the gate voltage. The exact value will depend on the VGSth of the FET and the current.

If VC5X is 44 or 46V the BQ76940 is likely damaged.

The BQ76940 may be damaged by the 44V on REGSRC, once the cause of the problem is fixed check if the part still works, but you should replace it before needing reliable operation..

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BQ76940: BQ76940