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AM5728: AM5728/TPS659037 Cold Weather Performance

Stephen Newberry
Prodigy 50 points
Part Number: AM5728
Other Parts Discussed in Thread: TPS659037,

We believe we have seen an issue in our application and would like confirmation. We are using a 3rd party SoM on our custom carrier board. We noticed during testing that we could not get the SoM to boot in cold temperatures (this was observed around 3°C). Lab testing confirmed this on multiple boards. Behavior showed as the PMIC (TPS659037) REGEN1 never coming high, and AM5728's RSTOUTN never coming high either.

Through extensive troubleshooting, we found that we could resolve the issue by lengthening the rise time of our 3.3V supply to the SoM. (As alluded to in this TI document: http://www.ti.com/lit/an/swca302/swca302.pdf). Our default/previous ramp time was 1ms, and we resolved it by extending ramp time to about 80ms (far longer than the 90mV/ms requirement in that document). FYI, this 3.3V rail is powering VCC1 on the PMIC.

I would like to specifically ask - has TI seen any issue at all with cold weather performance on this SoM/PMIC? Are you aware of any limitations regarding power supply ramp time aside from what is mentioned in TI documentation?

Thanks,

Stephen

  • 0
    TI__Guru**** 393215 points
    Hi Stephen,

    TI does not test 3rd party boards, so we cannot comment on this SOM's behavior. I am moving this over to the Power Management forum, where our experts have better knowledge of PMIC behavior. They will comment here.
  • 0
    TI__Genius 10000 points
    Stephen,

    The 90 mV/ms requirement is enough time for the POR of the TPS659037 to correctly power up across temperature. You should not need 80ms to turn on VCC1. I am not sure what is causing this cold temp start up issue, but it is likely not the POR requirements, if you need 80ms to turn on the device. Feel free to share the schematic of the PMIC portion if you want feedback.

    Thanks,
    Nastasha
  • 0 in reply to Nastasha
    Prodigy 50 points
    Hi Nastasha,

    Thanks for getting back to me. I can't share the schematic due to it being a 3rd party module.

    Thanks,
    Stephen