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DRV8432 Bootstrap capacitor

DC Bandara
Prodigy 10 points

Hi,

I am using DRV8432 in full bridge mode to drive motor driven liquid control valves (5A max current and 13.8V). 

I need to know whether there is a formula to calculate the bootstrap capacitor for different frequencies? I need to calculate the correct capacitor value for 1kHz and 500Hz. I can't find any formula in the datasheet.

Please help. Can you please let me know whether DRV8432 has a SPICE model?

Regards,

DC

  • 0
    TI__Mastermind 26065 points

    Hi DC

    From the driving ability point of view, the 0.1uF boot cap will be fine to charge the internal MOSFET at all PWM frequecy settings. The reason why we need higher boot cap at lower frequency is to prevent the voltage on the boot cap drain down below BST_UVP and causing protection or non-eough voltage to turn on the MOSFETs, during the time the PWM is not switching. A big boot cap helps maintain the high side gate voltage above the proper level longer. 

    You should be able to cover as low as 500Hz with 1uF to 2.2uF boot caps. When use that big boot caps, please add the 5-ohm resistor to GVDD to limit the initial charging current into the boot caps. Other wise the gate driver may be damaged by the huge inital charging current which takes longer time to build up the voltage on a big boot cap than a small one.

    Also you should keep in mind that the boot caps need to be refreshed / recharged all the time by switching the low sides.

    Best regards,

  • 0 in reply to Wilson Zuo
    TI__Mastermind 26065 points
    We will check if the SPICE model is provided. But if you can't find in ti.com, it may not able to be provided.

    Best regards,