• State
  • Locked Locked
  • Replies 4 replies
  • Subscribers 31 subscribers
  • Views 449 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV8432 - PVDD capacitance

YIts Ab
Prodigy 100 points
Other Parts Discussed in Thread: DRV8412

Hi ,

I'm using DRV8432 on Parallel Full bridge mode (PFB)  , PVDD = 24V and the current for the each side of the motor is up to 5 A.

I wonder if  1000uF isn't too big for that application?

Can i reduce the capacitance?

 

thanks

YITS

  • 0
    TI__Guru** 114905 points

    Hi Yits,

    The 1000uF used on the EVM is intended for up to 14A continuous. If the motor is 5A continuous, then lower the capacitance is acceptable. As you are running the motor, watch the ripple on PVDD to make sure it is acceptable.

    By the way, if using only 5A have you looked at the DRV8412? It can handle up to 6A continuous and 12A peak in parallel mode.

     

  • 0 in reply to Rick Duncan
    Prodigy 100 points

    Thanks 

    "then lower capacitance is acceptable" .. how much? 500uF? 300uF?

    we use this device because we maybe will need it for extra more application/

    so , can u be more specific?

  • 0 in reply to YIts Ab
    TI__Guru** 114905 points

    Hi YIts,

    As we are discussing only the driver, it seems that 470uF should work. If this capacitor is also powering other parts of the board, then you may need a larger value.

    One option is to pick a footprint that works for multiple value capacitors (330uF, 470uF, etc). This will allow you to pick the cap that you desire.

    Are you asking for more specifics on the cap value or something else?

  • 0 in reply to Rick Duncan
    TI__Expert 8885 points

    Yits,

    There are various factors which decide the value of bulk cap at PVDD.

    1. To filter out ripple in PVDD due to ripple present incoming power source
    2. To filter out ripple in PVDD due to high frequency switching current drawn by  H-bridge circuit. Two things affect this, PWM switching frequency and power rating. Higher switching frequency leads to lesser cap, but higher power rating means higher peaky current, which would require bigger capacitor value.  
    3. To meet filtering for any  standard EMI requirements
    4. Hold-up requirement in case of power interruption.
    5. Breaking requirement, if you need to break the motor with high deceleration rates, you will face over-voltage across PVDD, if cap is small.

    From first two factors, I can recommend based on my experience that if you’re input is DC source (without much ripple i.e. from Battery) and you are going to operate above 10Khz, 4.7uF per  watt would good selection. Note that this is ball-park figure solely based on my experience; you would be better judge to select right value based on your end application needs.

    Best Regards

    Milan