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TMUX1574: TMUX1574RSVR mux issue during SPI signals transmission

venish s
Prodigy 10 points
Part Number: TMUX1574

Tool/software:

Hi team,


we are using TMUX1574RSVR in our project. we are facing issue when we transmit SPI signals through that part.

Issue:

we are transmitting SPI signals with clock frequency of 125khz with the voltage level as 5V,

while doing so we observed that the SPI signals are not as expected. while probing the signals at both ends we found out that my input signals is as expected but, my output at bank A is not as expected. upon further investigation we found out signals from pin 3 (miso) is always Low. we checked slave device and its works fine.

hence we replaced the MUX. Even after  mux replacement  we are facing issue in bank B  (8th pin) is always low and the Bank A signals are now as expected.

Kindly confirm the cause for it and please suggest us to take care if suppose this error reappears.

Thanks and regards 
Venish S

  • 0
    Guru 297930 points

    Please show the schematic, including all components that are connected to the MISO line on both sides of the switch.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    Hi h,

    Please find the attached image



     

  • 0 in reply to venish s
    Guru 297930 points

    The schematic looks OK.

    If replacing the chip moves the problem to another pin, then this sounds like a soldering problem. I'd guess that there are solder bridges at or below the package.

  • 0 in reply to Clemens Ladisch
    Prodigy 10 points

    I checked pin to pin connectivity in board that's is fine, I guessing the MUX internal issue, why the MUX pin failure ?

  • 0 in reply to venish s
    TI__Mastermind 18980 points

    Hello Venish,

    I agree with Clemens on this and in addition the normal operation of the mux shouldn't be causing the error you see.

    This mux has a bandwidth of 2GHz and should be more than capable to pass the 125kHz 5V signal. This device is actually recommended for spi applications.

    Is there any other information you could provide that would help me and Clemens?

    What is the state of the select pins when you try to pass your signals?

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 10 points

    Hi ,

    Please find the attachments kindly your reference,

    this captured from master device input of MUX Device.

    below capture  took from MUX output of B channel.



    below capture took from MUX output of A channel.

    even the same part IC using many sections and many boards but this only one section issues there and also attached LOT IC Part, please find the below picture.

  • 0 in reply to venish s
    TI__Mastermind 18980 points

    Hi Venish,

    Thanks for the pictures here and I can help try to figure out what is going on here.

    Like Clemens said there could be a soldering issue and intern something on the board is pulling  1 out of the 4 on signal paths down.( Based of your waveforms)

    Is there a way you can take one of the "failed" units and verify the mux works independently of the system to make sure all the channels work.( There is possibility that one of t]he channels could be getting damaged during you system operation and this would help us find out)

    Also could you see what the supply current of the "failed" units is?

    Please let me know what you think and we can continue to work on this.

    Regards,

    Kameron

  • 0 in reply to Kameron Hill
    Prodigy 10 points

    Hi ,

    we checked pad to trace connectivity with multimeter that is fine in the board. What is the reason for MUX Issue ?

  • 0 in reply to venish s
    TI__Mastermind 18980 points

    Hi Venish,

    While there is still a possibility Clemens initial response is correct,right now there isn’t enough information to clearly say the multiplexer units you are using are the direct cause of the incorrect operation in your system.

    I personally suggest testing the 2 “failed multiplexer units” and see if they can pass signals through all the io pins. The testing of the multiplexers independently will let us know if they are the problem or not.

    Also, is there a way you can try a third multiplexer unit on the board and see if that device operate properly?

    Additionally if there is any other information you could provide that could help us find the issue here that would be much appreciated.

    Regards,

    Kameron