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DRV8353M: nFAULT always low and no output

Mitcham Tuell
Prodigy 150 points
Part Number: DRV8353M

I'm working on a design using the DRV8353HMRTAT. I originally designed for the DRV8353FHRTAR, but had to populate with the HM instead due to availability. I believe they are the same except for safety rating and temperature range. I'm having trouble getting the part to behave the way I think it should. A PWM input produces no output and the nFAULT line appears to be low all the time, even during and after I pulse ENABLE low for 30us. 

I am only using 2 of the three outputs. MODE is set to 3x PWM (47k to GND). INHA and INHB are the PWM inputs, INLA and INLB are pulled high through a 10k resistor, INHC is floating, and INLC is tied to GND. I see ~5V on DVDD output and ~16V on VGLS output. VM is 16V for now, although we also need it to work at 54V. 

I originally didn't have a pull-up on nFAULT, but I added one and it's still low all the time. Continuity check shows it is not shorted to GND.

GAIN is set to 10V/V, drive current to 100/200mA, and VDS set to 0.4V. The FETs I'm driving are FDMS8090 dual packages. Gate resistors 22 ohm.

Any ideas on what I might be doing wrong?

Thanks,

Mitcham

  • 0
    TI__Mastermind 19610 points

    Hello Mitcham,

    Thanks for posting to the MD forum. I will review your post and provide feedback tomorrow, thank you for your patience!

    Best,

    Isaac

  • +1
    Prodigy 150 points

    It seems we solved our own problem. We determined from the fault table that the VGS overvoltage and VSENSE overcurrent faults were probably the problem. We tied the VGS pin to GND to disable it and it didn't fix the problem. Then we shorted both C-channel current sense inputs to GND and it worked! The datasheet was not clear from anything we could find about whether you can leave those floating, but I guess the answer is that you can't without causing unpredictable readings on the current sense and potentially triggering an overcurrent fault.

  • 0 in reply to Mitcham Tuell
    TI__Mastermind 19610 points

    Hey Mitcham,

    I am glad you were able to get the fault condition sorted out and thank you for the datasheet feedback!

    Best,

    Isaac