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SN74LV541A: Question about a negative input voltage.

Kazuya Nakai59
Guru 20620 points
Part Number: SN74LV541A

Hello guys,

One of my customers is evaluate SN74LV541A on their own board.

In the evaluation, they found that SN74LV541A input signal voltage reached -900mV.
At this moment, they have the following question.
Could you please give me your reply?

Q.
We know this negative voltage violates the absolute maximum rating.
But we think it may be no problem if the period of the negative voltage is very short.
Is there any time when it is no problem?
Is it no problem if the negative voltage is less than 10ns?

Your reply would be much appreciated.

Best regards,
Kazuya.

  • 0
    Guru 268140 points

    There is no maximum time for which a lower voltage is allowed.

    The purpose of this limit is to protect the clamping diodes from burning out. You could instead limit the clamp current to less than 20 mA. According to the IBIS model, the worst-case current for −900 mV is −44 mA. So you need a series resistor to limit the current, or properly terminate the trace.

  • 0 in reply to Clemens Ladisch
    Guru 20620 points

    Hi Clemens,

    Thank you very much for your reply and I'm sorry to be late my response.
    Your reply is very helpful for us.

    Thank you again and best regards,
    Kazuya.