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Original question:

1:1spst Analog switch with LVDS select inputs

Spikes at TMUX6112 output

Md Faisal Rahman
Prodigy 170 points
Other Parts Discussed in Thread: DSLVDS1048, TMUX6112

Hello

  1. I am using TMUX 6112 to implement an analog gate in combination with DSLVDS1048. But my output looks problematic. At the time of swiching, spikes are observed. The yellow waveform is the input, the green one is the output and the blue one is the select pulse to the MUX.

I don't know if it normal for these switches or not. Please help.

Thank you

Faisal

  • 0
    TI__Expert 3515 points

    Hi Faisal,

    This does not look like typical behavior for the TMUX6112. Could you please provide a schematic to help with debug?

    Also, it looks like the input signal is being driven before the select pin receives the logic high value. The mux needs a small amount of time(~100nS)  to turn on before a signal can be passed.

    Thanks,
    Tyler

  • 0 in reply to Tyler McGuire
    Prodigy 170 points

    Hello Tyler

    Thanks for replying. I think the problem is with the LVDS receiver (DSLVDS1048) which is producing undesirable spikes at channels which are not suppose turn on. Here is a picture of this. the green waveform is a channel which is showing spikes at the instant when any other channel signal make a transition. 

  • 0 in reply to Md Faisal Rahman
    TI__Expert 3515 points

    Hi Faisal,

    Sounds like that could be the source of the spikes. Have you tried to remove the mux, short the desired path, and then see if the system works as expected?

    I am not familiar with the LVDS device you are using but is there a termination capacitor needed? I found this application note that may be helpful: How to Terminate LVDS Connections

    Thanks,
    Tyler