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SN74LVC157A: 32/16ch 2:1 mux

PRAHLAD Supeda
Expert 5175 points
Part Number: SN74LVC157A
Other Parts Discussed in Thread: SN74CBTLV16292, TMUX646, SN74CBT16232, SN74CBTLV16211, TS3A27518E

As per the design requirement, 32 digital lines are required to swap the signals. The below Quad part is available but needs to use 8nos to achieve the requirement so please suggest a 16-bit or 32-bit 1:2 MUX that provides the switching 32 signals at once.

 https://www.ti.com/lit/ds/symlink/sn74lvc157a.pdf?ts=1669011966757&ref_url=https%253A%252F%252Fwww.ti.com%252Flogic-voltage-translation%252Fspecialty-logic-ics%252Fdigital-multiplexers-encoders%252Fproducts.html

  • 0
    Guru 270970 points

    Digital muxes buffer their inputs and outputs. If you do not need buffering, you can use passive switches, i.e., analog switches.

    16-channel devices like the SN74CBT16232 work only with a 5 V supply. At 3.3 V or 2.5 V, there is the SN74CBTLV16292 (12 ch. = 3 chips), which has internal 500 Ω pull-down resistors on the disabled inputs. The largest general-purpose device is the TMUX646 (10 ch. = 4 chips).

    Alternatively, use multiple 1:1 switches like the SN74CBTLV16211 (16 ch. = 4 chips total, plus maybe an inverter for the control signal).

  • 0 in reply to Clemens Ladisch
    Prodigy 40 points

    Thanks for the suggestions. SN74CBTLV16292 does not suitable for the application due to internal pull-down. 

    SN74CBT16232 works only with a 5 V supply but a 3.3V IO level is acceptable on input and output. Please confirm.

    TMUX646 seems good advice but a BGA part and difficult to rework. Also as per the application, single-ended signals are required to swap so please confirm that it can support single-ended mode also.

  • 0 in reply to Nilesh Mittaliya
    Guru 270970 points

    The SN74CBT16232 is old and was designed for TTL signals with a high-level voltage of about 3.4 V. So your signals between 0 V and 3.3 V are supported. (It also accepts 3.3 V on the control inputs.)

    You can use the TMUX646 with single-ended signal. But I just noticed that the TMUX646 does not guarantee signals up to its positive supply, so you would need a 5 V supply, too.

    All ten-channel switches are BGA. The next larger switch would be the TS3A27518E with six channels.