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bq24616 / External gate resistor on /ACDRV pin

S.Satoshi
Guru 21685 points

Hi Everyone,

Please let me ask about external gate resistor on /ACDRV pin. The datasheet recommend to use 1kohm but it looks too large as gate resistor generally. So please let me ask following question.

  1. Please let me know the reason you recommend 1kohm
  2. Can I use smaller value or zero ohm? And then do you have any concern?

Best Regards,

Sonoki / Japan Disty

  • 0
    TI__Expert 5565 points

    Satoshi-san,

    The reason for that 1kOhm is for protecting the /ACDRV pin during hot plug scenarios. We have noticed spikes on the /ACDRV pin being coupled through the Cgd parasitic capacitance of Q1, so we placed a 1kOhm resistor to protect the pin.

    In a switching FET like Q3 and Q4, I agree that 1kOhm too high for series gate resistance, but Q1 and Q2 (and BATFET) are not switching FETs and have very slow turn-on times. Therefore, there is no impact to efficiency by putting a 1kOhm resistor there.

    Is there a reason you want to switch to a smaller value on the external /ACDRV resistor? Are you seeing issues?

  • 0 in reply to Smriti B
    Guru 21685 points
    Hi Smriti,

    I understood the reason of 1kohm resistor on the gate of AC FET. My customer want to shorten turn on time of AC FET so they are considering to use smaller value.

    Best Regards,
    Sonoki
  • 0 in reply to S.Satoshi
    TI__Expert 5565 points

    The turn-on time can be changed by changing the value of C14: