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DRV8323: operation question

user021864
Intellectual 2145 points
Part Number: DRV8323

Hi, 

I wonder if i can operate the driver for testing under below condition: 

VM is only apply to 8323 but not the power stage of IGBT or MOSFET

There will have voltage same as VM be at V drain, I wonder if this is normal for the driver. 

Since it's a sense pin input, it should not have voltage output, is this correct? 

thanks for your help.

  • 0
    TI__Genius 14487 points

    Hello user021864,

    You should be able to power the DRV8323 while not powering the MOSFET bridge. The VDRAIN pin is used to sense the high-side MOSFET drain, so it is not an output. I agree that you should still connect it to the same VM net as the DRV8323 IC.

    Edit: VDRAIN needs to be connected to the same net as the MOSFET bridge supply.

  • 0 in reply to James Lockridge19
    TI__Intellectual 2145 points

    Hi, 

    If i am able to power DRV8323 and not power the MOSFET bridge, why there will be output at the MOSFET bridge?

    Why there is an voltage equal to VM is been measured at Vdrain pin?

    Thank you.

  • 0 in reply to user021864
    TI__Genius 14487 points

    Hello user8323,

    I misunderstood your original question. I can ask our design team, but I need to know the following.

    1) How does the customer separate the supply of the power FETs from the device VM? Can you please provide a block diagram or a schematic?

    2) Does the customer have the ENABLE pin high or low when they measure VM on VDRAIN with this condition?

    Also, I updated my previous post. Please see the edit.

  • 0 in reply to James Lockridge19
    TI__Genius 14487 points
    Hello user8323,

    The reason you see VM on the VDRAIN net when the H-bridge supply is not powered is because there is a leakage path through the charge pump, out the SHx pin, and up the body diode of the high-side FET. While you may measure this voltage on VDRAIN or SHx, the leakage path will not be able to supply enough current to drive anything unintentionally.