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SN74LV4052A: Using SN74LV4052A to multiplex UART

Part Number: SN74LV4052A

Hi Team,

Our customer would like to use SN74LV4052A multiplexer for UART signal as shown in the schematic diagram below. Is this possible? I understand that UART uses TX and RX almost simultaneously but the SN74LV4052A will have to switch 2 signals from 2 multiplexers at a time. The pullup resistors are not yet included in the schematic diagram but will be added later.

Regards,

Danilo

  • Hi Danilo,

    From what is included on the schematic nothing looks wrong.

    I know you said that you haven't added the pull-ups to the schematic yet - but just some notes as you continue on this design:

    1. INH should be held low for device to be enabled - to prevent issues with floating logic pins I'd use a pull-up/pull-down to always have a default state on the pin.

    2. Same as with INH - the Select pins (A/B) should also have defined logic so adding pull-downs/pull-ups here helps keep the switch always in a defined state when in operational VDD ranges.

    3. All unused I/O pins can be left floating since UART is generally lower speed and reflections aren't a huge concern. However it is still recommended that these pins be terminated to ground using 50 Ohm resistors - but the risk for low speed applications to not follow this recommendations is very low basically neglible.

    Besides that it looks good!

    If you have any other questions please let me know!

    Best,

    Parker Dodson

  • Hi Parker,

    Thank you very much for your feedback and suggestions.

    Regards,

    Danilo