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MSP430FR2433: Amount of Time Needed to Energize Port Channels

Thomas Foxcroft
Expert 2981 points
Part Number: MSP430FR2433

In the Power Supply Sequencing section of the data sheet (p. 21 of SLASE59F), a specification called SVSH Propagation Delay [to] Active Mode says that the microcontroller takes 10 μs to reach active mode from an off state. Do I understand that spec correctly? It takes 10 μs from an unpowered state to active mode. Am I missing anything?

  • 0
    TI__Mastermind 27435 points

    Hi,

    It should means that the MCU is in active mode, then a SVS reset accurs, MCU will take maximum 10us back to active mode.

    Best regards,

    Cash Hao

  • 0 in reply to Cash Hao11
    Expert 2981 points

    So from an unpowered, off state, this microcontroller needs 10 μs to reach the active operating mode? This is specifically in the scenario where the MCU starts unpowered and ends in the active mode. That scenario only takes 10 μs, correct?

  • 0 in reply to Thomas Foxcroft
    Guru 92251 points
    Thomas Foxcroft said:
    So from an unpowered, off state, this microcontroller needs 10 μs to reach the active operating mode?

    I think tWAKE-UP-RESET needs to be considered in the delay taken from an unpowered off state:

    Where tWAKE-UP-RESET has a typical value of one millisecond.

    As well as tWAKE-UP-RESET need to consider:

    • The time taken for the supply voltage to reach VSVSH+
    • Any external circuit connected to RST
  • 0 in reply to Thomas Foxcroft
    Guru 35570 points

    It should also be remarked on that this is before any code gets executed.

  • 0 in reply to Chester Gillon
    Expert 2981 points

    Chester:

    Your line of rationale sort of coincides with what I’m concerned about: energizing the port channels before any voltage signal is placed onto them from the outside. That scenario could cause some damage. I should have mentioned that.

    For the interface circuit at DVCC, letting R equal 1 Ohm, the conventional amount of capacitance to be 10.1 μF, and Vcc at 1.8 volt, I calculate a delay of about 0.0202 ms before the voltage supervisor sees 1.8 for SVSH, and then I add another 10 μs for the for the propagation delay to the channels.

    After the microcontroller has powered up, I don’t think I have to worry about any delay caused from a wakeup from any LPM, because the PMM will disable and enable the channels appropriately.

    With tWAKE-UP-RESET, you’ve pointed out the reset scenario, which we assume is caused by a CPU crash. The microcontroller’s power rails will be energized throughout that scenario, so the risk of any damage to it from an existing outside signal going into a channel is, I think, very low.

    What are your thoughts about it? Have I missed anything?

  • 0 in reply to Thomas Foxcroft
    Guru 92251 points
    Thomas Foxcroft said:
    Your line of rationale sort of coincides with what I’m concerned about: energizing the port channels before any voltage signal is placed onto them from the outside.

    Does ESD Diode Current Specification help?

  • 0 in reply to Chester Gillon
    Expert 2981 points

    It sure did. Thanks for following up.

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