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DRV8334: BST cap sizing

Keith Keller
Expert 7250 points
Part Number: DRV8334

Tool/software:

Hello,

Is there any limitation to the size of the cap used for Cbst on the DRV8334?  Any concerns with a cap up to 2.2uF (or larger) in value?  

I see a recommended value of 1uF to 1.5uF in the datasheet.

Thank you Keith

  • 0
    TI__Genius 15475 points

    Hi Keith,

    This is really dependent on what the customer might be willing to deal with. Using a Cbst capacitor larger than what the datasheet recommend might be more demanding on GVDD to recharge the caps, especially at startup. This is especially relevant if all 3 low side MOSFETs are on, which will result in all 3 bootstrap capacitors recharging at the same time. This may cause a dip in the GVDD voltage in the attempt to charge up the Cbst capacitors, which may lead to a GVDD undervoltage fault. I think they'd be able to increase the GVDD cap if they're seeing that 2.2uF Cbst is too demanding but a large GVDD cap would also mean a slower initial power up for the device.

    Have they calculated their Cbst value using this formula? is that where the 2.2uF value is coming from?

    Regards,

    Yara