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CD74HC4067-Q1: Usage questions

Daniel Wang (auto)
Expert 4200 points
Part Number: CD74HC4067-Q1


Hello team,

We have some questions when use the part in ZCU, kindly ask your insights.

1. The chip is powered by 5V, and the input pin receives 3.3V. After the channel is enabled, a 5.3V level appears at the COMMON port. What could be the reason?

2. Is there any problem if analog and digital signals are mixed on adjacent input ports? The isolation between adjacent channels should be fine, right?

3. For unused input pins, should they be left floating or connected to ground?

BR,

Daniel

  • 0
    TI__Expert 7165 points

    Hi Daniel,

    1. Have you checked the connections of each pin to make sure everything is soldered properly?

    2. There should not be a big issue putting analog/digital signals on adjacent ports. There is usually some cross talk between channels, which increases as the frequency increases, but there should still be separation between the channels.

    3. At higher frequencies, unused input pins should be tied to ground through a termination resistor (usually 50ohm).

    To help me better understand the application, could you share a schematic as well as the frequency of the signals/ if any square waves are being used?

    Thanks,
    Katy