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DRV8801: nFault signal close slowly to ground

Jin-U Kim
Prodigy 10 points
Part Number: DRV8801

Tool/software:

When the device is switched on, the nFault signal is initially open. After a few seconds, the nFault signal slowly starts pulling the voltage down to low. This is visible via the connected LED with a pull-up resistor.

What could be the cause of this issue?

  • 0
    TI__Mastermind 19380 points

    Hello,

    The nFAULT pin will be pulled logic low with fault condition. This pin is an open-drain output which does require an external pullup resistor. 

    Are you evaluating the DRV8801 on our DRV8801EVM?

    There could be any number of reasons why a fault is being triggered, could you provide a more detailed description of how you are testing? Are you driving a load? Whats the load type? Whats the supply voltage?

    Best,

    David

  • +1
    Prodigy 10 points

    Hi David,

    we have identified the root cause. The issue was that the motor driver is in sleep mode and only wakes up when it is activated. While in sleep mode, the outputs are likely in a tristate condition, which in some cases may result in the output being slightly driven. What’s strange is that the output is configured as open-drain, so I would have expected it to be either low or high.