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DRV8311: The output voltage of nFAULT pin issue

Zhang Liang
Genius 4125 points
Part Number: DRV8311

Hi,

We uset the DRV8311 in our project, and now, we measure the output voltage of nFAULT pin is 1.0V when the power on, and we change the RnFAULT from 10Kohm to 5.1Kohn(Same as the datasheet), the output voltage is also 1V, pleaes kindly review below schematic and provide your comment is there any error, thanks.

  • 0
    TI__Genius 12231 points

    Hi Zhang, 

    Can you provide the voltage waveform on the supply nFAULT / MODE / GAIN / SLEW is being pulled up to? Are any of those pins experiencing lower than expected voltage as well?

    Lastly, can you check if any of the fault registers have been triggered? 

    Best Regards,

    -Joshua

  • 0 in reply to Joshua Maize
    Genius 4125 points

    Hi,

    Please refer to below waveform for nFAULT power on/ power off:

    The MODE pull down with 47Kohm and there are no waveform;

    The GAIN pull down with 47Kohm and there are no waveform;

  • 0 in reply to Zhang Liang
    TI__Genius 12231 points

    Hi Zhang, 

    Thank you for the additional info and I apologize for some of the confusion on the device/parameters used.

    Looking over the schematic again I notice nSLEEP (pin 24) is being pulled-up to AVDD as well, is that correct? I believe nSLEEP has an internal pulldown resistor, so can you remove that resistor and also give a reset pulse to it to reset the device?? 

    Further, can you check the other major input/output pins to determine if there are any other abnormal waveforms, as well as provide what voltage this device is operating at?

    I'd like to understand if there is potentially a fault being tripped at all which will help narrow down the possible causes. 

    Best Regards,

    -Joshua