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TPS659037: OFF2ACT Power Sequence Timing

Patrick Ruf
Genius 4810 points
Part Number: TPS659037
Other Parts Discussed in Thread: TPS22990

Hi,

We use the TPS6590379 in one of our designs. Now we checked the OFF2ACT sequence against the data in the User's Guide (sliu011f, page 15).

We can see that the time between SMPS7 and SMPS12 is approximately the 550us (please see picture 1).
But when we measure the time between REGEN1 signal and RESET_OUT signal we have 1524us versus 1100us (please see picture 2) and time between REGEN1 and LDOUSB is 918us versus 550us (please see picture 3).

We use an external switch (TPS22990) that is switched on with REGEN1 to switch on the 3.3V main rail.

Is there an error in timing of the User's Guide? If not, what could be the problem in our design?

Thanks and best regards,
Patrick


Picture 1: SMPS7 on CH4, SMPS12 on CH3


Picture 2: REGEN1 on CH4, RESET_OUT on CH3, 3.3V main rail on CH1


Picture 3: REGEN1 on CH4, LDOUSB on CH3, 3.3V main rail on CH1

  • 0
    TI__Mastermind 37030 points
    Hi Patrick,
    Thanks a lot for your questions on the device! It looks like the 918us from REGEN1 to LDOUSB is an issue. The device expert has been notified about the issue. She will verify it on the bench and then give you a better answer next week since the left 2 days in this week are holidays.
  • 0
    TI__Genius 10000 points
    Patrick,

    It looks like the power sequence is coming up in the correct order. Is this the case? What is the concern with this delay? I know that the digital rails come up faster than the LDOs or SMPSs. The LDOs and SMPSs will have a slight delay from when the rail sees the enable signal to when the rail begins turning on (~250us typical).

    Thanks,
    Nastasha
  • 0 in reply to Nastasha
    Genius 4810 points

    Nastasha,

    Thanks for your response.
    Yes, the sequence is coming up in the correct order. We compare the timing with the timing diagrams and times in the TPS6590379 User's Guide to make shure that our hardware is doing fine.
    If some timing is not as documented this is a reason for us to have concerns.
    The time from the rising edge of REGEN1 to the start of the ramp of LDOUSB is documented as 550us. We measure around 900us. So we ask ourselvs whether we have a problem on our hardware or if there is a documentation problem. We don not have something like a "golden" board to compare with when bringing up the first prototype boards. So maybe TI can have a look into the TPS6590379 firmware to figure out what the correct timing must be. Or maybe TI can measure the same signals on their boards. If the times are the same, we are happy. If not we really worry.

    Best regards,

    Patrick

  • 0 in reply to Patrick Ruf
    TI__Genius 10000 points

    Patrick,

    I checked our program, and it shows a 650us delay between REGEN1 and LDOUSB. I can update the user guide to reflect this timing. Also, the 650us delay plus the typical of ~250us delay between the LDO being enabled and the rise of the LDO output will give you the ~900us you are observing.

    Thanks,

    Nastasha

  • 0 in reply to Nastasha
    Genius 4810 points
    Nastasha,

    Thanks for checking in the firmware. I'm shure an update in the user guide will help others as well.

    Best regards,

    Patrick