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SN74CBT16233: Mux or analog switch suggestion

Bo Xian Yeh
Intellectual 1315 points
Part Number: SN74CBT16233

Hi Team,

If customer want to use one processor logic I/O to drive 50 loaded I/O, do we have suitable solution?

Please help to advise. Thank you.

  • 0
    Guru 295730 points

    When you say "I/O", do you mean input or output or both?

    Do you need to drive multiple ones at the same time?

  • 0
    TI__Mastermind 48257 points

    Hi Bo,

    I do have a few questions:

    1. Do you want to be able to drive all 50 loads at once or do you want to use one output that is switched across all 50 loads?

    2. What is the voltage being passed to these loads - and is there a frequency component or is it a DC signal?

    3. What are the loads that are being driven - i.e. what is the impedance of the loads that are being driven?

    A few things to note about our analog switches are:

    1. Our analog switches are passive devices - they do not drive anything, so if a drive source is needed a driver is also needed in the design. 

    2. If you need all 50 devices connected at once, a switch isn't what you need - you would need some type of fanout buffer; if this is the case I will loop in the correct people into this thread to address the question as TI may still have suitable solutions - it just may not be an analog switch/mux.

    3. If an analog switch/mux can work in the application (depending on the exact use case) it would have to be a multi-chip solution realistically with 8 muxes at a minimum just so you are aware. 

    Please if you can share a bit more detail into the application I can see what the next steps are to finding a suitable solution.

    Best,

    Parker Dodson

  • 0 in reply to Parker Dodson
    TI__Intellectual 1315 points

    Hi Parker,

    Please my update as below. I/O is single direction input and output signal.

    1. Do you want to be able to drive all 50 loads at once or do you want to use one output that is switched across all 50 loads?

    Ans : Customer want to use SPI port (Master) to do communication with 50 slave.

    2. What is the voltage being passed to these loads - and is there a frequency component or is it a DC signal?

    Ans : 3.3V clock signal and DC signal

    3. What are the loads that are being driven - i.e. what is the impedance of the loads that are being driven?

    Ans : Load is CPLD and core chip is Xilinx 9572

    Please help to check if we have suitable solution. Thank you so much.

  • 0 in reply to Bo Xian Yeh
    Guru 295730 points

    What is the frequency? How many signals need to be switched per slave? Is there a MISO signal?

  • +1 in reply to Bo Xian Yeh
    TI__Mastermind 48257 points

    Hi Bo,

    1. Since there is only 1 controller in the system what signals are being switched? Are you switching a Chip Select (CS) line to multiple devices or are you trying to fan out the clock signal to 50 devices, or are you trying to switch the SPI bus between different peripherals?

    2. If you are trying to switch the CS lines to multiple devices - how fast will the host need to switch between multiple devices?

    3. If you are trying to just switch a SPI bus to multiple peripherals are you using 3 or 4 wire spi, and what is the clock frequency - I can't give a rec. without the clock frequency.

    4. If you are trying to fan-out the signal; a switch isn't what you need - and a fanout buffer would be needed. 

    If you could clarify the use case I will be able to better see if we have a solution with analog switches/muxes.

    Best,

    Parker Dodson