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MSPM0L1306: undefined startup behavior

Daniel Hardegger
Prodigy 60 points
Part Number: MSPM0L1306

If a voltage of 1 Volt is applied to the PA16 when the microcontroller (Revison A) is started, it shows different behaviors. Either it starts normally and recognizes the signal, it does not recognize the signal or it is in a mode in which nothing works until a reset is forced. The 1 volt signal at PA16 is present at the same time or slightly earlier (100ms) than the supply. Do you have an explanation for this behavior or at best a solution how to fix it?

  • +1
    TI__Guru 56685 points

    Hello Daniel,

    I suspect the intermittent error has to do with the timing of when that signal is applied to PA16 relative to when supply is reaching VDD pin of the device. If you are supplying 1V to PA16 before the device sees a voltage on VDD, then you are violating datasheet specifications for the device. By doing this, you are potentially creating a power path from that IO through the ESD structure to bring up the part. This can cause stability problems or the device not behaving as expected.  This is very common in most MCUs, which is why the below highlighted specification will be seen on most datasheets. 

    The solution is to sequence the power up so this situation doesn't happen. You could do this several ways. One would be having a signal between the MSPM0L and the source of this voltage. You would then not send out this voltage until the MSPM0 is powered up. Or you can gate it with a FET, etc. If it won't affect your signal coming in, you can also place a low pass filter potentially on the line. This way you could adjust the RC time constant so that the cap doesn't charge up to a voltage faster than VDD is propagated to the device.