This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

  • TI Thinks Resolved

TLV2780: TLV2780IDBVR

Part Number: TLV2780

Hello!

We bought one reel TLV2780IDBVR and the Settling time is bigger as always. We use them for a long time and yhis time have a problem.

How can we check if it is original? can we send you the samples to check?

we are planning to use this component for a long time so we need to be sure that the parameters did not change or if they changed we need to know that it is really your decision

  • Hi Elena,

    My apologies that you are seeing a shift in the settling time in your system. It would be very helpful for us if you could attach:
    * The relevant portion of the schematic and describe your application a little
    * Scope-shot of acceptable settling time
    * Scope shot of unacceptable settling time.

    Settling-time is not a guaranteed parameter in the datasheet so it is possible that with process variation that the devices will shift a little bit in performance. However, with a well designed stable system that has enough phase margin, your settling time shouldn't change too much. I would like to analyze your circuit's stability and make sure you're not right on the edge of stable.

    -Paul
  • Hi Elena,

    have you made any changes to the design? I ask, because the settling time heavily depends on gain and capacitive load.

    Kai
  • In reply to kai klaas69:

    Our schematik has not changed.

  • In reply to Elena Silinskaya:

    Hi Elena,

    It is possible that the original design was on the edge of stable and with a little parameter shift in the devices it no longer is. The best way for us to help you is if you provide the relevant portion of the schematic and some screen shots.

    Thanks,

    Paul

  • In reply to Paul Goedeke:

    We check a few chip from old delivery and new in the same board. We saw a difference in the output signal on the same board and the same input signal.

    The part is sheme.

  • In reply to Elena Silinskaya:

    Hi Elena,

    Thanks for sharing part of your circuit - can you post the image a little bigger? I'd like to help you but it is impossible for me to read.

    Thanks!
    Paul
  • In reply to Paul Goedeke:

    Is it ok now?

  • In reply to Elena Silinskaya:

    Yes! Thank you :)

    -Paul
  • In reply to Paul Goedeke:

    Hi Elena,

    One more thing - are you able to provide:
    * Scope-shot of acceptable settling time
    * Scope shot of unacceptable settling time

    I'll take a look at the stability of this circuit and see if there are any potential issues there.

    Best,
    Paul
  • In reply to Paul Goedeke:

    Hi Elena,

    I ran a stability analysis on your circuit and have some concerns. My simulation shows only 25 degrees of phase margin which is generally not enough for robust stability. Our ICs will shift parameters device to device so we recommend at least 45 degrees of phase margin to account for part variation and temperature.

    It is possible that the reason you are seeing issues now is that a new lot of devices has had a little bit of specification drift (while still meeting the datasheet values) but now your circuit, which has marginal stability, is unstable.

    To fix this issue, I recommend a simple fix of tweaking the value of C15. Right now I believe that it is too large - if you reduce the value of this cap to around 400pF, you'll have a more robust and stable circuit.

    It would still be useful to see the screenshots of good and bad behavior, that will greatly help with our diagnosis if you'd like further help. I've attached a TINA simulation for you to look at.

    Thanks,

    Paul

    TLV2780_TIA_Stability.TSC

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.