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DRV8350F: GND pin 30 - digital GND?

Part Number: DRV8350F

Hi,

I'm designing a board with the DRV8350F and I'm not sure, how I should connect pin30 (GND). 

My GND plane looks like this:

So the SLx are connected to the mid pad of the IC and to the PWR GND. Pin30 is currently connected to my digital GND, as you can see above. What I fear is a latch up effect.

Kind Regards,
Sebastian

  • Hello Sebastian,

    The pin 30 GND should be tied to the same net as the thermal pad, and please take care of the following:

    You should trace the following paths to make sure they are as short as possible:

    • VGLS paths:
      • DRV835x VGLS pin to VGLS capacitor
      • VGLS capacitor to DRV835x GND pin
      • VGLS capacitor to bottom of the sense resistor
      • top of sense resistor to low-side MOSFET source
      • low-side MOSFET gate to DRV835x GLx pin

    Thanks,

    Matt

  • Thanks Matt,

    One more question about two options I have with the DRV8350F:

    VM can be connected to VDRAIN or a separate power supply. I have a low noise +12V buck regulator available

    and I'm unsure, if I should connect VM to the +12V buck regulator or VDRAIN? VDRAIN can vary by reuperation in between +48VDC to +57VDC when the chopper triggers, so this will be a way more unstable way. I personally would prefer the +12V variant, but is this even possible to supply VM with +12V while VDRAIN is up to 57VDC? From the datasheet, VM minimum is 9VDC, but I cannot find a dependency from VDRAIN.

    Another question that came up for me is, how fast VM should be switched on? Can I take some ms of time to switch the voltage to it?

  • Hi Sebastian,

    I would recommend that you review this app note (LINK). DRV835x can operate in either mode. A lower VM results in less power dissipation.

    It is OK to switch on VM slowly. The pin has an undervoltage lockout and it will not drive the motor until the threshold is exceeded.

    Thanks,

    Matt