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BQ24725A: BQ24725A charge query

Star Xu
Genius 9645 points
Part Number: BQ24725A
Other Parts Discussed in Thread: BQ24725

Hi 

The customer design with BQ24725A.

4 cells, charging voltage 16.8V. As shown in the screenshot, when the battery is charging, the upper and lower bridge MOSFT waveforms, and the lower bridge waveform is a triangle (ideally should be a square wave), what is the reason for this?

12. VBAT-BQ24725.pdf

 

Waiting for your reply.

Thanks

Star

  • 0
    TI__Genius 17350 points

    Hello Star,

    That waveform does look unusual. The customer should turn everything off and use an ohm meter to measure the impedance between the LODRV pin and ground to check if there is a high impedance that is affecting the waveform. The LODRV pin or the gate pin of the lower bridge MOSFET could also be damage and need to be replaced.

    Regards,

    Christian

  • 0 in reply to Christian Moyer
    TI__Genius 9645 points

    Hi Christian

    Thanks for your reply.

    The customer directly measure the chip (Pin14 to Pin15, 18 resistance or impedance)

    Multimeter resistance measurement: LODRV is 160K ohms, HIDRV is 7M ohms;

    Multimeter diode measurement: LODRV is 331, HIDRV is 667;

    5pcs were tested, the data are the same, Does the chips normal?

    Waiting for your reply.

    Thanks

    Star

  • 0 in reply to Star Xu
    TI__Genius 17350 points

    Hello Star,

    I don't see obvious issues with the resistance measurements. I attached an image of the LODRV waveform that I measured using the EVM, to show how a normal LODRV waveform looks.

    I don't see obvious issues with the PCB design either. There are multiple possibilities on what could be affecting the waveform such as a damage IC, a damage  MOSFET, or a damage/ faulty BR13 resistor.

    My recommendation would be to order the EVM board for further testing. I would also recommend confirming there is zero resistance between the LODRV pin and the gate pin of the lower bridge MOSFET on the customer board.

    Regards,

    Christian