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DRV8912-Q1: VM input capacitor

Akihiro Hirata
Expert 4780 points
Part Number: DRV8912-Q1

Hello team,

There are 2 VM pins.

Each have the CVM1 and CVM2 respectively, so total 4 caps.

Do you recommend to use total 4 caps? or are we able to consolidate it to 2 caps(= 1 x CVM1 and 1 x CVM2 for both VM pins)?

Regards,

Hirata

  • 0
    TI__Expert 5980 points

    Hi Hirata-san,

    The two capacitors on both input pins serve different purposes for the system. One is a Bulk capacitor used for energy storage to allow the output voltage not to dip when a input step signal is given to the input. Theses bulk capacitors are usually large electrolytic capacitors to provide a steady input power supply when switching. The other is for current ripple reduction which are generally ceramic capacitors that help to reduce noise or ripple. 

    Best,

    David

  • 0 in reply to David Medis
    TI__Expert 4780 points

    Hi David-san,

    Thank you.

    Let me explain again.

    There are 2 bulk cap and 2 ceramic cap in total in the datasheet as shown the original question.

    Is it possible to reduce it to 1 bulk cap and 1 ceramic cap?

    I think ceramic cap must be as close to the VM pin as possible, so 1 ceramic cap for each pin is at least needed.

    How about the bulk cap?

    Do you think 2 bulk cap is needed? or 1 bulk cap can be also acceptable?

    Regards,

    Hirata

  • +1 in reply to Akihiro Hirata
    TI__Expert 5980 points

    Hi Hirata-san,

    Only one bulk capacitance could be used as long as it is large enough for both pins. It is still recommended that two ceramic capacitors are used for both VM pins because they are to be placed close to the pins and the pins are not located next to each other. 

    Best,

    David

  • 0 in reply to David Medis
    TI__Expert 4780 points

    Hi David-san,

    Thank you for your answer. I understood.

    I appreciate your support.

    Regards,

    Hirata