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Dead time of LM25037

Takahiro Nishizawa
Genius 5575 points
Other Parts Discussed in Thread: LM25037

We have a question about LM25037.

Dead time is written in datasheet p.6.

40(min)

75(typ)

105(max)

We want to know the interpretation of dead time variation.

Variation are 35nS(min and typ) and 30nS(typ and max).

Variation is about ±40%.

Which is correct?

We stray with time(--nS) or % to check the variation of dead time.

Best regards,

Takahiro Nishizawa

  • 0
    TI__Mastermind 25570 points
    Hello Nishizawa-san

    The specification limits are that the dead time will be within 40ns to 105ns and this includes temperature variations. You can expect a typical dead time of 75ns - . The specification limits are not symmetrical around the typical value but I don't have test data to show the distribution of test results, that is the mean and standard deviation.

    The best approach is to use the time limits given in the data sheet because those are the limits which we use during the test process.

    If you need the distribution of test results, mean and standard deviation - please let me know and I'll ask for them. There will be some delay in getting that data because of the Christmas Holiday period.

    Regards
    Colin
  • 0 in reply to Colin Gillmor
    Genius 5575 points
    Thank you for your answer!


    We have a new question.
    In datasheet, dead time is 40nS to 105nS when is Rrt2 is 15kΩ.
    Please tell us the variation of dead time when value of Rrt2 is changed.
    Is the variation of dead time always about 35nS from typ 75nS if the Rrt2 is changed?
    Should we consider the variation in ±--%?

    For example, when we set the dead time 250nS,
    Is the variation about 35nS from typical time or about ±40% from typical time?


    Best regards,


    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    Genius 5575 points
    Thank you for your support!

    How is your situation?
    We are waiting for your answer!

    Best regards,

    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    Genius 5575 points
    Thank you for your support!

    We hope earlier answer.

    We have a new question.
    In datasheet, dead time is 40nS to 105nS when is Rrt2 is 15kΩ.
    Please tell us the variation of dead time when value of Rrt2 is changed.
    Is the variation of dead time always about 35nS from typ 75nS if the Rrt2 is changed?
    Should we consider the variation in ±--%?

    For example, when we set the dead time 250nS,
    Is the variation about 35nS from typical time or about ±40% from typical time?


    Best regards,


    Takahiro Nishziawa
  • 0 in reply to Takahiro Nishizawa
    TI__Mastermind 25570 points

    Hello Nishziawa-san

    I've been OOO for the Christmas/New Year holidays. I'll try to answer your question as soon as possible.

    Regards

    Colin

  • 0 in reply to Colin Gillmor
    Genius 5575 points
    Thank you for your support!

    We understand your situation.
    We hope earlier answer.

    Best regards,


    Takahiro Nishizawa
  • 0 in reply to Takahiro Nishizawa
    TI__Mastermind 25570 points
    Hello Nishizawa-san

    I expect that the graph of Dead-time variation vs RT2 would have an initial offset due to fixed internal delays (section 7.4.3 in the DS) which limit the minimum dead time to 50ns typ. At larger nominal dead-dimes the variability would be a combination of the fixed internal delays plus a contribution from the variation of the timing components in the oscillator.
    The initial offset would be a larger proportion of the variability for short dead times than for longer dead times. So the overall effect would be that the percentage variability would reduce as the nominal dead time increases. Unfortunately we don't have any test data to quantify this variation so I'd suggest that a conservative approach would be that the customer design for a ±40% variation in dead time

    Has your customer chosen a particular dead time value? and what value of RT2 are they planning to use?

    Regards
    Colin