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PGA450-Q1: STATUS1 failed

Petr Dada
Prodigy 30 points
Part Number: PGA450-Q1

Some pieces in our utrasonic sensor production (output check) have set some bit in STATUS1 register, so internal self-test is failed - specifically we have detected bit 4 (MBIST_FAIL) and bit 6 (TRIM_FAIL) is set. Could you please tell us what exactly means failed tests and what can be impacts on sensor work (obstacle measurement, communication?). Sensors with failed STATUS1 (b4 and b6 set) seems to be OK in all other our tests. However, because our control units reports error if the STATUS1 register is not zero in some connected sensor, this is the problem. Our important customers return sensors with failed STATUS1 (meantime 5 sensors from 5000). Could you recommend what bits of STATUS1 register are necessary to check in startup? Is there some way to reduce these fails?

  • 0
    TI__Mastermind 27950 points
    Hello Petr,

    The b4 (MBIST_FAIL) and b6 (TRIM_FAIL) failures may indicate that the STATUS1 register is read too soon upon POR. The system must allow at least 5ms to expire after POR before attempting to read the STATUS1 register. Does your system first read b5 (MBIST_DONE) to determine if the built-in self-test is complete before reading the STATUS1 register?

    For the five devices failing STATUS1, have you tried waiting for at least 1 second before reading back STATUS1? Do the flags eventually clear?

    The MBIST_FAIL could indicate that the FIFO RAM and external RAM have become corrupt. Similarly, the ASIC trim value may have become corrupt for similar reasons. Did these units always return a failing STATUS1, or did the failure flag only recently?

    Depending on how corrupt the ASIC trim is, the results may or may not be impacted severely. IF the RAM memories are compromised, then saving the echo data dump to FIFO memory may not be possible to perform the time-of-flight distance calculation.

    The more critical flags are b0-b3. Any over/under voltage/current will impact the analog reference, which will offset or prevent the analog front end's multiplier from scaling the return correctly.
  • 0 in reply to Akeem Whitehead
    Prodigy 30 points
    Hello Akeem,

    Thanks for answer.

    Our PGA450 software in ultrasonic sensors returns value of STATUS1 register in special LIN Slave Response Frame, so it is always read minimally 20 ms after POR. Three sensors return STATUS1 = 64 (bit 6 set) and two sensors return STATUS1 = 16 (bit 4 set), bit 5 is clear in all cases. When I read STATUS1 a few second after POR, STATUS1 value is still same (failed). All five PGA return failing STATUS1 always - repeatedly in laboratory. Can STATUS1 fails depend on conditions as temperature, supply voltage, ... ?

    We forgot to check STATUS1 in end of our production line, so we don't know if these five sensors were failed in our production, or they had failed at the customer. I supposed, in TI, you check the status of all chips and supply to customers only pieces with clear STATUS1 register?

    We add the STATUS1 check to our production a few days before and also we are checking all produced sensors in stock. Until now we checked about 200 pieces and we found two sensors with failed STATUS1 - one with bit 6 set and one with bit 4 set!