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DRV8871-Q1: DRV8871-Q1 VM Bulk Cap

Jack CCY
Intellectual 1695 points
Part Number: DRV8871-Q1

Hi team,

Greetings. I have a question about the VM bulk cap of DRV8871-Q1.

The parameter is that VM=12V coming from automotive battery, normal working current=1A, stall current=2.5A.

Duty cycle is 100% only using high or low voltage level to controll.

Can I just use a 1uF ceramic cap here? Is there any drawback?

What if I use 10uF ceramic cap or a bulk cap?  Any problems?

Customer said they used 0.1uF cap on VM pin when they used two half bridge chips before, there was no problem.

Look forward to your reply.

Thank you.

Best Regards

Jack Chen

  • 0
    TI__Genius 14487 points
    Hi Jack,

    If the duty cycle is 100%, then the bulk capacitor size should not matter for the most part. The purpose of the bulk capacitor is to supply most of the current to the motor during PWM. It also reduces ripple from the power supply to the board. If there is nothing on the board that switches, and the power supply rails have low ripple, then your customer can probably use a smaller bulk capacitor on their board.

    For future reference, here is an application note that addresses bulk capacitor sizing: www.ti.com/.../slta055.pdf

    Be sure to correctly use decoupling capacitors recommended in the datasheet.