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SN74LVC1G07: Absolute Maximum Ratings transient spec

Hailiang Zhang
Genius 11280 points

Part Number: SN74LVC1G07

Tool/software:

Hi Expert,

Customer found that there is a -680mV overshoot at the output side of SN74LVC1G07, see the attached waveform, and they are asking for overshoot or undershoot spec of the SN74LVC1G07. 

1, could you pls help check is there a Absolute Maximum Ratings transient spec?

2. Is it possible that our device can cause this undershoot?

Regards,
Hailiang

  • 0
    Guru 317750 points

    1. There is no transient specification. The absolute maximum rating must not be exceeded, not even for a short time. But a clamping current of up to 50 mA is allowed, and if the IBIS model is to be believed, a current of 50 mA is reached only at output voltages below −1.05 V.

    2. The SN74LVC1G07 itself simply connects to the output pin to GND, so it cannot generate voltages below GND. The undershoot is generated by the entire board, i.e., by the combination of the different impedances of the SN74LVC1G07's output, the trace, and the receiving device's input. To prevent reflections, the trace must be properly terminated. Try source termination, i.e., adding a 33 Ω series resistor directly at the output pin.

  • 0 in reply to Clemens Ladisch
    TI__Genius 11280 points

    Hi Clemens,

    Clemens Ladisch said:
    a current of 50 mA is reached only at output voltages below −1.05 V

    The current rating of 50mA and the voltage rating of -0.5V must be met at the same time, right? In other words, although the current rating is within the spec range, it is still unacceptable for the voltage spec not to be met?

    Regards，
    Hailiang

  • 0 in reply to Hailiang Zhang
    Guru 317750 points

    No, footnote (2) allows you to exceed the voltage limit in this case.

    There is a plain silicon diode from GND to the pin. For voltages above −0.5 V, no noticeable current flows.

  • 0 in reply to Clemens Ladisch
    TI__Genius 11280 points

    Hi Clemens，

    Thanks for your comments. The footnote(2) is "The input and output negative-voltage ratings may be exceeded if the input and output current ratings are observed."

    Could you pls double check does it mean "The input and output negative-voltage ratings can be exceeded as long as the input and output current ratings are observed."

    Regards,
    Hailiang

  • 0 in reply to Clemens Ladisch
    TI__Genius 11280 points

    Hi Clemens,

    I know little about the IBIS model, but I am wondering, why is the VO abs voltage rating defined as -0.5V instead of -1.05V? Do you have any suggestion?

    Regards,
    Hailiang

  • 0 in reply to Hailiang Zhang
    Guru 317750 points

    The IBIS model is not the datasheet, so the diode's forward voltage characteristics are not actually guaranteed.