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SN74LV541A: Output Waveform Ringing Issues

Conor
Guru 10210 points
Part Number: SN74LV541A
Other Parts Discussed in Thread: SN74HCS541

Tool/software:

Hi,

We have been using the SN74LV541APW in our products since 2017 without any issues. However, starting with the production batch from October 2024, we have observed irregular output waveform ringing, which has resulted in operational malfunctions in our applications.

Key details:

  • The issue did not occur in any production batches prior to October 2024.
  • This ringing phenomenon has impacted the reliability of our products.

We kindly request your assistance in investigating the following:

  1. Possible changes in manufacturing or materials that could contribute to this behavior.
  2. Recommended steps or mitigations to resolve or prevent the issue.
  3. Any additional data or analysis required from our side.

Attached to this inquiry are waveform samples and test results demonstrating the observed ringing.

We look forward to your prompt response to help address this matter.

Thanks,

Conor

  • 0
    Guru 287360 points

    This input signal violates the specified Δt/Δv limit. You must use a device with Schmitt-trigger inputs.

    There is no P2P replacement. The SN74HCS541 works only if you change the pull-up voltage to the buffer's VCC.

  • 0 in reply to Clemens Ladisch
    Guru 10210 points

    Hi Clemens,

    We have been mass producing with a similar application configuration since 2017, but this phenomenon has become frequent in the October 2024 mass production lot. This ringing waveform affects the control of the application, causing problems with control not being performed as designed. We have also confirmed that the problem does not occur when replacing lot ① with lot ②.

    ①Chip image where ringing is likely to occur

    ②Chip image where ringing is unlikely to occur

    Also, looking at the following application, the application note states that the input transition time should not be violated, and that in the worst case, a dull slew rate waveform can cause oscillation.


    https://www.ti.com/lit/an/scba004e/scba004e.pdf

    As you pointed out, the circuit diagram I presented does not meet the specified input transition slew rate. However, this ringing problem has not occurred in applications that have been mass-produced since 2017.

    What could be the cause of this problem?
    Please let us know if there have been any changes to the factory, internal IC design, 4M changes, etc.

    Of course, we will take measures to address the slew rate in the future, but we need to clarify why this problem started occurring.

    Thank you for your cooperation.

    Conor

  • 0 in reply to Conor
    Guru 287360 points

    The SN74LV541APW was discontinued in April 2023.

    For the SN74LV541APWR, an entirely new die was announced in PCN 20230327003.1.

  • 0 in reply to Clemens Ladisch
    Guru 10210 points

    Hi Clemens,

    Do you have any idea what causes the ringing between the new die and the old die? If there are any changes in the IC design, please comment.

    Thanks,

    Conor

  • 0 in reply to Conor
    Guru 287360 points

    The new die is more sensitive to slow edges, i.e., the rise/fall rate where oscillation starts is nearer the specified limit.