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SN54S04: SN54S04 Input Pin abs max

Alpha H
Genius 10855 points
Part Number: SN54S04

Hi team,

 

I have a question regarding the SN54S04 Vabs max on the input pin. The datasheet says that the absolute max voltage on the input pin is 5.5V. Does this max rating also apply to transient overshoots? My customer is trying to apply 7V for about 4nS on the pin. Will this degrade the part and cause potential damage?

 

If the abs max cannot be exceeded, would it be possible to add a Schottky diode between the input pin and Vcc to clamp the transient spike?

 

Thanks for the help,

 

Arthur Huang

  • 0
    TI__Guru 62930 points
    Arthur,
    This does violate the absolute max input specifications, and will degrade the device.
    Use of a TVS can protect the input from harming the device.

    If this answers your question, please click "Verify it as the answer"
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    TI__Genius 10855 points
    Hi Wade,

    Thanks for the response. Are there any recommended TVS diodes for this device?

    Thanks,
    Arthur
  • 0 in reply to Alpha H
    TI__Guru 62930 points
    I am not very familiar with using TVS or Schottky diodes for input protection.
    I will check with my counterparts in the commercial group to see if there are any recommendations.
    From a little bit of research, TVS diodes may have higher capacitive loading on the input than a Schottky solution and also may not have low enough clamping voltages to help.

    Any option to change devices to one that allows higher than 5.5V for input? Possibly the LS04 in the same datasheet?

    I will see if I can come up with a recommendation.
    Regards,
    Wade
  • 0 in reply to Wade Vonbergen
    TI__Genius 10855 points
    Hi Wade,

    I agree with the assessment on the TVS, I also don't think that the TVS can respond to a 4ns spike in time. Unfortunately, the 5.5V is also a requirement.

    I think that adding a Schottky from the input to Vcc will work the best. Since the drop across the Schottky is only ~0.4/0.5V, it will react faster than the internal diodes if the spike happens.

    Let me know what your counterparts think.

    Thanks!
    Arthur
  • 0 in reply to Alpha H
    TI__Guru 62930 points
    Thanks Arthur.
    Another option to consider/evaluate. Adding series resistance to help minimize overshoot from reflection.
    Anywhere from a 100 to 250 ohm series resistance could help.

    Regards,
    Wade