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Original question:

TMUX1208: Looking for 1:8 demux part with 1.8V logic compatible

Output level

Chris Schramm
Intellectual 590 points
Part Number: TMUX1209
Other Parts Discussed in Thread: TMUX1574

Dear TI-Team,

We want to offer an UART Multiplexer which is controlled from a 3V3 MCU and 3V3 logic level UART.

TMUX1209 looks like a perfect fit as I can see that 1.8V logic is good enough for the inputs. But I can‘t find output levels (VOL and VOH).  For SA1 = 1.5V, what will DA be? 1.5V? Or will it get shifted?

  • 0
    TI__Expert 3900 points

    Hi Chris,

    Most devices in the TI switches and multiplexers portfolio are passive fet based devices. They do not have buffers and thus do not have a VOH or VOL spec.

    The output will be equal to you input unless you have some sort of voltage divider to shift the output.

    The TMUX1209 can be used for this application of UART. However, the TMUX1209 is a 4:1 mux with 2 channels. Are you planning to use the mux for multiple UARTs?

    If you are trying to switch between only 2 UARTs you can use a switch such as TMUX1574.

    Can you provide an image of what you are trying to accomplish?  This way I can recommend the best device.

  • 0 in reply to Dakotah
    Intellectual 590 points

    Hi Dakotah, and thanks for the quick reply.

    I was misled because of the 1.8V tolerant control logic (which I realize just means that a 1.8V MCU is fine)

    This will be some sort of I/O expander board and the TMUX was meant for offering up to 4 additional UARTs. It would be awesome if there was a mux device which includes a level shifter option but I understand that such a device doesn‘t exist.

    I‘ll go with an UART mux for now and add a level shifter ic to the slave device for now

    For reference:

    LSF0102QDCURQ1 looks like a perfect fit