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DRV8312: Output voltage when in reset

Joe Williams3
Prodigy 40 points
Part Number: DRV8312

Hi,

Could you tell me what the expected output voltage is on OUT_X when the reset lines are asserted?

We're currently seeing ~10.5V whilst the reset lines are LOW, with VDD/GVDD_X = 12V and PVDD_X = 18V.

I can't find mention of this in the datasheet and couldn't see from the diagrams where this voltage would be coming from.

Thanks,

Joe

  • 0
    TI__Guru 62730 points

    Joe,

    If you add a resistor to GND does this voltage dissipate?

    Do you have a motor connected at this time?

    I think you are seeing a small leakage voltage.

    Regards,

    -Adam

  • 0 in reply to Adam Sidelsky
    Prodigy 40 points

    Hi Adam,

    Thanks for the quick response.

    The voltage doesn't dissipate when connecting a resistor to GND, it does drop though as if it's forming a potential divider. With GVDD_X = 12V, adding a 10k between OUT_X and GND drops to voltage to 3.92V, suggesting a ~21 kOhm resistor to GVDD_X. However, on removing the resistor the voltage returns to ~10.5V.

    It looks like it's a path between OUT_X and GVDD_X, if I vary the GVDD_X supply, the voltage at OUT_X changes. The voltage doesn't change if I vary PVDD_X.

    During this testing the motor wasn't connected, I believe it behaves the same with the motor connected though.

    Could it be something to do with the bootstrap circuit?

    I'm looking for confirmation that this is expected behaviour. We do some diagnostic checking at startup in our application, just to make sure the controller is responding correctly to our inputs, so need to know what voltage we should be seeing on the OUT_X pins when held in rest.

    Thanks,

    Joe

  • 0 in reply to Joe Williams3
    Prodigy 40 points

    Hi Adam,

    Have you had any further thoughts on this?

    Best regards,

    Joe

  • 0 in reply to Joe Williams3
    TI__Guru 62730 points

    Joe,

    In RESET mode the BST charging circuit is still active so you will see the BST charging current and any internal high side gate drive leakage.

    Regards,

    -Adam