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TL072: Power on ramp rate requierment

Mochi
Genius 3995 points
Part Number: TL072
Other Parts Discussed in Thread: , LM317, LM337, TL074H

Hello,

Our customer wants to know the requirement of "Power up ramp rate" for their internal system Design Review.

On SLOS080R datasheet, I could find following specification for TL07xH device.

6.17 Electrical Characteristics: TL07xH

"Turn-On Time At TA = 25°C, VS = 40 V, VS ramp rate > 0.3 V/μs    60 μs(TYP)

But there is not TL07x device specification, is that different specification between TL07xH?

 

One more question is how can we read TL07xH specification?

We are familiar that Power up ramp rate is specified like "maximum 60V/us and minimum 0.3V/us"

However what is meaning of TL07xH specification format? Typical xxV/60us?? and minimum 0.3 V/μs

 

Regards,

Mochizuki

  • 0
    TI__Guru**** 151776 points

    Hello Mochizuki-san

    'Turn on time' and 'power up rate' are very different parameters. 

    The TL072H seems to be referring to a power up reset time. For the POR to work as intended, the Vs ramp rate should be faster than 0.3V/us rate.

    The TL072 classic does not have POR circuit so there is no minimum ramp rate but for Vs less than normal range, output may not be as expected.     

    There are no maximum Vs ramp rates specified. 

    What is the application's Vs ramp rate?

  • 0 in reply to Ron Michallick
    Genius 3995 points

    Ron-san,

    Thank you for your reply, I got the difference of TL072H function and specification.

    At this time, the customer just want to pass the design review but we do not have actual ramp rate.

    We have seem legacy OPAs and Converters are not specified ramp rate.

    Generally speaking what is safe area of Vs ramp? Slower than 1(V/usec) is good number?

    Regards,

    Mochizuki

      

  • +1 in reply to Mochi
    Guru 140200 points

    Hi Mochi,

    there's no such limit for the TL072.

    Let's discuss some numbers. Assume the TL072 is powered by LM7815/LM7915 or LM317/LM337. Then during power-up the regulators can drive an output short-circuit current of 2.2A. Further assume that the regulator output and the TL072 supply pins see a 100nF decoupling cap each. Then the ramp rate at the voltage supply pins of TL072 would be

    dU/dt = I / C = 2.2A / 200nF = 11V / µs

    This situation would be fully normal and would not present a problem to the TL072.

    Because of this, limiting the ramp rate to less than 1V / µs would not be a good idea.

    Kai

  • +1 in reply to Mochi
    TI__Guru**** 151776 points

    Mochizuki-san,

    I tried fast Vs ramp rates (up to 100V/us) on TL074H (quad version of TL072H) without any issues. So any rate should be acceptable to TL072H. I always discourage hot switching (instantaneous power that usually causes inductive voltage spikes)

  • 0 in reply to Ron Michallick
    Genius 3995 points

    Hello Kai and Ron,

    Thank you very much for your realistic suggestion.

    Normally LDO over current limitation will be bottle neck with decoupling cap capacitance value.

     

    Regards,

    Mochizuki