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MSP430F2618: MSP430F2618

Joseph Casey
Prodigy 160 points
Part Number: MSP430F2618


Greetings.

I have some processor boards on which the program sometimes fails to self start upon power up.

However when such a "freeze" happens, the program starts if I activate the RST/NMI pin.

I shall post schematics and start up code later, but first I would like some information about start up voltage.

My start up circuit has an R/C pair which slowly ramps up AVcc and DVcc to 3V. ( the power is supplied by a 3.3V regulator when program starts)

The time constant of the R/C circuit is long (about one minute)

Is that very slow ramp up a bad idea? Could it adversely affect the internal Brownout Reset (BOR) circuit?

Regards.

Joseph Casey.

  • 0
    TI__Guru 56685 points
    Hello Joseph,

    If you are having issues, then a slow ramp could definitely be a cause. You could get in a situation were your ramp is near the BOR power up voltage, but a voltage dip or fluctuation takes you back down. Or possibly the ramp is slow enough that the max BOR release time is not enough to ensure the device is at the min voltage needed to operate.

    if you do make it through the BOR threshold, then the device will start to operate normally. This could be an issue with a slow ramp if for say you are still ramping at around 1.8V, but one of the first things you do in your code is change the clock to 16 MHz. This would cause a Frequency vs Voltage violation of the part as the minimum voltage needed for 16MHz operation is 3.3V.

    In short, you can have some issues with a slow ramp, and if possible, the recommendation would be to speed up the ramp. Particularly in this case by reducing capacitance on the DVCC line.
  • 0 in reply to Jace H
    Prodigy 160 points
    Thank you Jace.
    It isn't possible at this stage to know if my problem is solved, bcause it is intermittent anyway.
    Your detailed information about start up process and clocks is something I can use to improve my start up hardware and code.
    JC
  • 0 in reply to Joseph Casey
    TI__Guru 56685 points
    Joseph,

    I'll mark this post as closed/resolved for now. If you reply back, we can re-open or start a new thread.

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