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DRV8860: Using as general open drain output

Miroslav Bozic
Intellectual 420 points
Part Number: DRV8860

Dear,

I am working on the Test Interface that will be used for functional testing of the specific control board at the end of the line and for troubleshooting in the exploitation. I need to integrate 8 channels of general open-drain outputs in my system. Since the DUT (Device Under Test) can be broken it is required that outputs are protected so Test Interface won't fail when the DUT produces short circuit or similar fault. I found DRV8860as very useful for my application and would like to integrate it into the system.

The only concern I have is whether DRV8860 outputs can be referenced to the voltage rail that is different than VM rail? I am wondering whether this can produce open load fault os something similar? 

Looking forward to getting feedback from your side.

Best regards.

  • 0
    TI__Guru** 114905 points

    Hi Miroslav,

    What it the VM rail and what is the output referenced voltage rail?

    This may be possible if the output voltage rail is less than the VM rail, but we would have to confirm.

    It the output voltage rail is higher than the VM rail, the internal recirculating diodes shown in the Functional Block Diagram will cause VM to rise to a diode less than the output voltage rail.

  • 0 in reply to Rick Duncan
    Intellectual 420 points

    Dear Rick,

    I can keep VM rail at 24V which is maximal voltage the DUT uses. This will keep output voltage rail bellow VM voltage. Below is a simplified schematic diagram of two examples that can be expected on my DUT. I need to interface similar inputs in order to test the DUT functionally.

    Please check and confirm whether this is a possible use-case or it is not so I can decide which way to go.

    Thanks best regards.

  • 0 in reply to Miroslav Bozic
    Intellectual 420 points

    Dear Rick,

    do you have any update on the topic?

    Regards.

  • 0 in reply to Miroslav Bozic
    TI__Guru** 114905 points

    Hi Miroslav,

    The simplified schematic should work, but there is one additional item to consider.

    A diode (anode at OUT1 and cathode at 5V) is needed to re-circulate the current and keep the voltage at the load below 5V + Vf. If this diode is not placed, the OUT1 voltage will increase to VM + Vf when the output is disabled.

    This could damage the load.

  • 0 in reply to Rick Duncan
    Intellectual 420 points

    Hi Rick,

    thanks for the answer. It seems like this is not the best way to go, I will try to find something similar to DRV8860 since there are too many things to be considered.

    Newer the less, thank you for the help you have provided.

    Best regards.