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SN74LVC1G99-Q1: strong under/overshoots and ringing

Miroslav Karkus
Prodigy 40 points
Part Number: SN74LVC1G99-Q1
Other Parts Discussed in Thread: SN74AUP1G99

We have found that strong under/overshoots and ringing occur on a clock signal due to the lack of an electrical termination (series resistor).
I could not find, but I wonder if there is an alternative for SN74LVC1G99QDCURQ1 which has an internal resistor to avoid these problems? Or is other solution?

Thanks.

  • 0
    TI__Guru* 96661 points

    Hi Miroslav,

    No, there aren't any 'little logic' (8 pins or less) logic devices with added damping resistors. Those are generally only added for buffers and line drivers for impedance matching to transmission lines.

    If you don't have a long transmission line (> 12cm), then it is more likely that you just have an underdamped system, or what we often refer to as a light load. Adding a load capacitor (33pF to 47pF) or adding a series resistor (or both) can improve the signal.

    Ringing also can show up when testing with standard oscope probes due to the large loop size of the ground return path.

  • 0
    Guru 256980 points

    The SN74AUP1G99 has much weaker outputs, but no automotive qualification.