• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 28 subscribers
  • Views 122 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

DRV8426: Regarding undershoot

Daisuke Higa
Genius 3515 points
Part Number: DRV8426

Hi support team.

Is my understanding correct as following Figure?

If yes, the measured body diode VF value during the dead time period is 1.06V, and it is incomprehensible why it exceeds 1V.

Also, since this exceeds the absolute maximum ratings, is this considered a problem?

The measurement point is close to the device's output terminal AOUT1, so I don't think it depends on the layout.

The mainly parameters are below.

<Motor parameter>

Rs = 25ohm

Ls = 42mH

Best regards,

Higa

  • +1
    TI__Genius 16835 points

    Hi Higa-san,

    "If yes, the measured body diode VF value during the dead time period is 1.06V, and it is incomprehensible why it exceeds 1V.". Your understanding is correct. 42 mH is a very high inductance typical inductances of steppers are below 10 mH many below 5 mH. The body-diode of the FETs are not fast enough in this case with the higher kick-back voltage from the inductance. If you'd want to mitigate this situation use four additional fast Schottky diodes across the FETs to help comply with the absolute max specifications of the device. 

    Regards, Murugavel

  • 0 in reply to Murugavel4637
    Genius 3515 points

    Hi Murugavel-san

    Thank you for your advise.

    I understood well.

    Thanks!

    Regards,

    Higa