Just trying to put together a small USB switch for my own educational purposes and I am struggling a little with choosing an appropriate multiplexer for the D+ and D- lines.

My situation is that I want to be able to share a single USB port with 2 PCs, with the press of a button I want to be able to disconnect the USB port from one machine then connect it to the other. For this I am using a power mux for the +5v lines from the 2 machines and a USB mux for the data lines.

I found the FSUSB20 and FSUSB30 muxes but I can't choose which one is more suitable. For a start they both seem to be a DPDT switch, fine - that's what I am after, but:

  • The FSUSB20 sells itself as "bi-directional", the FSUSB30 makes no mention of that. Is this important?
  • The two ICs use different nomenclature for the pins, not sure if it's relevant or not?
  • The FSUSB20 is described as "1 port" whereas the FSUSB30 is "2 port". Why is this? They appear to be logically identical to me? Is this to do with the bi-directional thing?

Can someone help me choose what is the best out of these for my purposes? Or indeed recommend an alternative IC if neither of these are any good. The FSUSB30 is easier to get for me, but I was especially thrown out by the lack of "bi-directional" in the datasheet so wanted to make sure I was doing the right thing. Thanks!


1 Answer 1


USB signals always are bidirectional, and bidirectional switches based on transmission gates are not any more complex or expensive than other kinds, so it is not worth mentioning.

Both chips can be used as 1:2 or 2:1 switches. The different names do not matter; the behaviour is the same.

You know that these chips work for USB because they are designed for that. But you could just as well use any other analog switch with similar or better characteristics (high bandwidth, low resistanced and capacitance).


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