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DRV8837: Maximum peak current with capacitive loads

Conrad Hoffman
Prodigy 40 points
Part Number: DRV8837
Other Parts Discussed in Thread: DRV8212P

We use pairs of DRV8837 to drive 2-phase piezoelectric motors. They run near resonance, so capacitive and not a simple load. The peak currents can exceed plus and minus 2 amps (2 divisions on scope photo, yellow trace), but the duration is on the order of a microsecond. Is the absolute maximum current 1.8 amps regardless? We don't see any current limiting or thermal shutdown, but we're also near the deglitch time so maybe it doesn't come into play. Are we on the edge of trouble?

We also use the DRV8212P with the higher rating, depending on availability and our application. Are the two chips the same part, but selected for current capability, or completely different?

  • +1
    TI__Mastermind 22790 points

    Hey Conrad,

    2A for that amount of time should be fine as far as chip safety goes. If you look in Protection Circuits part of 6.5 Electrical Characteristics, the overcurrent deglitch time (tDEG) is 1us, so no matter what the current is it won't trip until it's seen >1.9A for 1us or more.  However, as you say I do think you're right on the edge of trouble if it does decide to trip.  I would ask how much of a problem it is if the device trips near the end of your ~1us signal and the device disables all the outputs for 1ms, and you can determine whether that would be noticeable or not in this use case.  

    The DRV8212P is basically a "refresh" of the DRV8837, designed to be a drop-in pin to pin compatible replacement for the DRV8837.  DRV8837 was released in 2012 (see the top right of the datasheet pages), whereas the DRV8212P was released in 2021.  If you can I would definitely recommend going with the newer part (DRV8212P).  

    TI also has Piezo Drivers and Haptic Motor Drivers if one of those might fit your application better.  Looks like the Haptic motor drivers have auto-resonance tracking.  And here are some other E2E posts that seem maybe similar:  Post 1 Post 2

    Regards,

    Jacob