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TPS65261-1: About PGOOD rising edge deglitch time

Kaji@PAN
Mastermind 7280 points
Part Number: TPS65261-1

Hello,

Looking at the data sheet for TPS65261-1, it states that PGOOD rising edge deglitch time is 512 cycles.
This value is TYP, do you have MIN and MAX information?
In my circuit, the switching frequency is 781kHz, but when I actually measure my circuit, the PGOOD deglitch time is 0.85ms.
In the calculation above with 512 cycles, it should be 0.655ms.
This difference appears to be large even when variations in switching frequency are considered.

Best regards,

  • 0
    TI__Expert 6175 points

    Hello,

    An answer will be posted beginning of next week.

    Best,

    Calan

  • 0
    TI__Mastermind 21250 points

    Hi,

    Thanks for reaching out. Actually we do not have min/max value for PG rising deglitch now and there also might be some variation for PG deglitch time. Could you please kindly let us know any of your concern or what can we support from our side?

    Thanks!

    BRs

    Lucia

  • 0 in reply to Lucia Gao
    Mastermind 7280 points

    Thank you for your answer.
    I would like to determine whether the actual measurement results are valid.
    I have two additional questions.
    1. Is it possible that the numbers for 512 cycles vary?
    2. Are there any factors that cause the rising reglitch time to vary apart from 512 cycles?
    For example, there may be some waiting time before and after counting 512 cycles.
    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 21250 points

    Hi,

    Thanks for your feedback. Could you please kindly let us know how you measured the PG rising deglitch time or do you have waveform? I would like to first check the measured result. A example: Force fb from 0.42V to 0.6V square waveform with 1Hz freq, trigger PG then you can get the deglitch time.

    Thanks!

    BRs

    Lucia

  • 0 in reply to Lucia Gao
    Mastermind 7280 points

    Thank you for your reply.
    Attached is the measured waveform.
    The time from when 2.5V becomes constant until PGOOD rises is measured.
    Also, correct my information.
    The switching frequency is set to 707kHz. Actual measurements vary between 699kHz and 710kHz.
    So PGOOD rising edge deglitch time should be 0.72ms to 0.73ms.
    Therefore, since the measured waveform is 0.85ms, there is a difference of about 0.1ms.
    Please let me know what causes this difference.
    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 21250 points

    Hi Kaji,

    Thanks for your feedback. Is 2.5V rail from Buck1/Buck2/Buck3? Could you please check the deglitch time after all three Bucks Vout are within the range?

    Thanks!

    BRs

    Lucia

  • 0 in reply to Lucia Gao
    Mastermind 7280 points

    In addition to 2.5V, there are 1.1V and 3.3V systems.
    After 1.1V and 3.3V have risen, 2.5V is finally started.
    It has been confirmed that 1.1V and 3.3V are within the setting range.
    So, please let me know your opinion about the difference in PGOOD rising edge deglitch time.
    Also, please give me your opinion on the questions I asked earlier.
    1. Is there any variation in the value of 512cycle itself?
    2. Variation factors other than 512cycle.
    3.The variation in switching frequency is 600KHz according to the data sheet, which is ±40KHz, so it is ±6.7%.
      707kHz is also calculated at ±6.7%, is there any problem?
    Best regards,

  • 0 in reply to Kaji@PAN
    TI__Mastermind 21250 points

    Hi 

    Thanks for your feedback! For the reason of this variation, I will check and get back to you soon.

    BRs

    Lucia

  • 0 in reply to Lucia Gao
    TI__Mastermind 21250 points

    Hi Kaji,

    The number of cycles might not be exactly the same as 512 cycles but there will not be much variation. Could you please try with another way to get more accurate PG deglitch time? Force fb from 0.42V to 0.6V square waveform with 1Hz freq, trigger PG then you can get the deglitch time. A waveform shown below for your reference. Usually PG asserted when softstart end. Sometimes softstart end will happen after Vout comes to yout target value.

    Thanks! Kindly let us know any of your concern.

    BRs

    Lucia

  • 0 in reply to Lucia Gao
    Mastermind 7280 points

    Thank you for your reply.
    Lastly, please tell me.
    What does it mean that the soft start ends after Vout reaches the target value?
    What are the conditions for soft start to end?
    Isn't the condition that the SS pin voltage reaches 0.6V (= output voltage becomes stable)?
    Best regards,

  • +1 in reply to Kaji@PAN
    TI__Mastermind 21250 points

    Hi Kaji,

    Sorry that it maybe makes you confused. Please refer to an example shown below. The ref voltage is 0.8V for below figure.

    Thanks!

    BRs

    Lucia