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TMS320F28034: Double check about the released time of reset pin during power on

Daniel Fang
Genius 11600 points
Part Number: TMS320F28034

Hi,

In the process of power on, what's the power voltage when reset pin is released?  Or how long about reset pin released time during power on. 

Below is our test result and hardware. The blue wave is power, red is reset.

On datasheet, it says it has 400-800us after POR event. Sorry for I don't know POR voltage threshold. Thanks.

  • 0
    Guru 30330 points
    Daniel,

    A few comments.
    Your power ramp is extremely slow. Is that 15 ms from start to finish? We don't specify a max or minimum ramp time, so I don't believe that there is any issues other than it being slow.

    I think what you are seeing is a factor of the slow ramp time. The MCU internals are slowly rising along with the VDDIO supply, until what looks like about 0.7 volts (top of the small hump in the reset signal). This is roughly about where the reset circuitry is able to actually assert the XRSn to 0. We also do not specify at what voltage the MCU recognizes the VDDIO power as good to release the reset you highlighted in your post.

    I am curious the reasoning for the Diode on XRSn. we do only recommend the Pullup resistor and cap to Ground. based on your question of the MCU behavior, I suspect that you are not using an external voltage supervisor. Is this correct?

    Thanks,
    Mark
  • 0 in reply to Mark Labbato
    Guru 30330 points
    Hi Daniel,

    Its been a bit since you last posted. I was curious if you still had questions.
    I will be out of the office until Jan 2 but have notified a colleague who may be able to follow up in the next week if necessary.

    Happy holidays,
    Mark
  • 0 in reply to Mark Labbato
    TI__Genius 11600 points

    Hi Mark.

    Thanks for your notice. Enjoy the time.

    Merry Christmas!

  • 0 in reply to Daniel Fang
    Guru 30330 points
    Daniel,

    I hope you enjoyed the holidays! Please let me know if you still have questions.

    Thanks,
    Mark
  • 0 in reply to Mark Labbato
    TI__Mastermind 42065 points
    Closing due to inactivity.

    Regards,
    Cody