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bq77908a current sensing

vivek kumar
Prodigy 50 points
Other Parts Discussed in Thread: BQ77908A

Dear TI Experts,

Assume the sense resistor interface to the bq77908a sees a pulsating current as shown in the attached image below. How will the safety IC interpret the voltage across the sense resistor?

  1. Is the amplitude of the voltage seen by bq77908a averaged or it will see the peaks for the period seen as in the waveform?
  2. If the duration of the peaks/spikes of the current are lesser than OCD trip delay of 180 ms, are we good?

Your quick response will be appreciated.

  • 0
    TI__Guru 54715 points
    The input pins do not average inside the IC, they are sampled. Generally we would expect some filter on the pins outside the part. The IC samples at ~ 30 us, if it sees a sample below the threshold it will re-start the timer. Of course if your waveform aligns with the part sampling such that it misses the low voltage portion of the waveform the part will trip.