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BQ76PL455A-Q1: BQ76PL455A-Q1 cannot get Fault_N Working

Alex Terry
Intellectual 625 points
Part Number: BQ76PL455A-Q1


Hi, Im using the BQ76PL455A-Q1 to monitor 16 cells, Ive set the over voltage and under voltage thresholds for the VSENSE inputs and set the under voltage threshold for AUX0, I have enabled these faults on the FO_CTRL register, when reading the individual fault registers when simulating a fault the fault is found. However when using the GetFaultStat() as written into the example code a 1 is always returned no matter if a fault is present or not. Having run some tests I can see that with no fault present the voltage is at ~3.3V, it seems when a fault is triggered it falls to ~1.8V, however it seems this is not low enough to trigger the GetFaultStat() when used. Any Help would be greatly appreciated.

Thanks,

Alex

  • 0
    TI__Genius 11480 points
    Hi Alex,

    Looking back at your schematic, it looks like you have FAULT_N tied to GIOA[0]. The GetFaultStat() function in the example code reads back the value from GIOA[1]. Try changing the argument in the function from 1 to 0 to switch to the other GPIO.
  • 0 in reply to David Wiest Jr
    Intellectual 625 points
    Hi David,

    Thanks for pointing that out, I completely overlooked those connections.

    Dont know how the device was being woken up at all at the moment but I shall try and make the change first thing tomorrow.

    Cheers,
    Alex
  • 0 in reply to David Wiest Jr
    Intellectual 625 points

    Hi David,

    I've tried switching the argument but unfortunately it hasn't worked either. After further testing I've found that the output on the FAULT_N lines from the BQPL455 is 0.8V when a fault is simulated (which still seems a bit high) but when measuring the GIO[0] pin I am reading 1.8V which seems like the pin is configured as an output rather than an input, the 1V difference seems to be being dropped across the series resistor. When there is no fault present both pins read 3.28V with no voltage drop across the resistor. Any idea on what could cause the input on the MCU side to not drop below 1.8V?

    Also Ive noticed that the Wakeup output (from now GIO[1]) doesn't toggle like the code suggests, instead it starts at 0V and then jumps to 1.8V when the code has been run and remains there, is this normal?


    Thanks,
    Alex