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SN74CBTLV3257: Can I pass 1.8V SPI signals through this part or CBTLV family parts?

Part Number: SN74CBTLV3257
Other Parts Discussed in Thread: TMUX1574

I want to use CBTLV switches to pass 1.8V signals. The CBTLV family are 3.3V and OE#, Sel are all 3.3v signals.  I am ok with that. But I don't know if I can pass 1.8V signals.  It seems that I should be able to. 

is this functioning like an analog switch?  like if I put a sine wave (amplitude of 1.8V), I get a sine wave on the other side?

  • Hello,

    The SN74CBTLV3257 allows for rail to rail switching which means that the device is capable of passing any signal up to supply voltage.

    Thanks!

    Bryan

  • Thanks. That is what I thought.  But then it begs the question. Why do I need TMUX family? It seems that when I query fro analog mux,  TMUX shows up, but not all CBTLV.  What is the difference except control signal voltage level and VCC level? are they both transmission gate based? 

  • Hi Jun,

    The newer TMUX devices often offer improved performance in many aspects. The newer version of this device is the TMUX1574 which offers better parametric performance (higher bandwidth, lower RON, lower CON, lower leakage) and several features that are not included on some older devices (such as fail-safe logic, beyond the rail capability, and 1.8V logic compatibility). As you can see, there are many advantages over some of these older devices, however, if you do not necessarily need those specifications, the CBTLV is a perfectly suitable multiplexer.

    Thanks!

    Bryan