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MUX507: connect 8 rs-485 connector to rs-485 transistor

Gary Teng
Genius 5440 points
Part Number: MUX507
Other Parts Discussed in Thread: SN65C1168E, , CD4097B, TMUX1308, SN74HC151, CD74HC238

Hi all,

 My customer want to design an 8 RS485 mux with MX507 + SN65C1168E. Is it ok for using MUX507? or other suggestion for the application?

Best regards,

Gary Teng

  • 0
    Guru 271820 points

    The RS-485 bus might have voltages outside your own supply voltage range, and might see strong ESD events. The SN65C1168E is designed to handle this, but not the MUX507.

    If your RS-485 bus is used in an environment where those problems can happen, then you have to add appropriate protection circuits in front of the MUX507. Alternetively, put the mux between the MCU and the transceiver (which would require eight transceivers).

  • 0 in reply to Clemens Ladisch
    Genius 5440 points

    Hi Clements,

     Any suggestion for 8ch mux between MCU and 8 SN65C1168E? Use 3 TMUX1380 or?

    Best regards,

    Gary

  • 0 in reply to Gary Teng
    Guru 271820 points

    The D signal does not need a mux. The only two-channel 8:1 mux cheaper than the MUX507 would be the CD4097B, which has lousy electrical characteristics at 5 V, so you should keep the MUX507, or use 2× TMUX1308.

    (For logic signals, you could use a digital demultiplexer like the CD74HC238 and a digital multiplexer like the SN74HC151, but those would not be simpler or cheaper.)

  • 0 in reply to Gary Teng
    TI__Mastermind 46427 points

    Hi Gary,

    Using 8  SN65C1168E, you would only need to Mux the R signal. Based on the above diagram, you will will have the same end result if you use a common D line, a common DE line, and then muxing the R signals. 

    For this I would suggest the TMUX1308, using the same VCC as the SN65C1168E.

    Best,

    Parker Dodson