PCA9544A: May I have some question for PCA9544A and ... ?

Hey TAlex,

"What's different between Multiplexer (PCA9544A)  and  Switch(PCA9546A) ?"

Thanks for this question, quite a few people do not realize there is a difference which can cause problems if they wanted a certain functionality.

A switch has the ability to enable MULTIPLE channels at the same time. A multiplexer can only enable 1 channel on at the most, at a time. You can use a switch the same way as a multiplexer (where you enable 1 channel at a time) but you won't ever be able to enable multiple channels at the same time with a multiplexer. Simply put, a switch can be a multiplexer but a multiplexer can never be a switch.

Each has their advantages and disadvantages. A multiplexer, you will never run into the problem on accidentally enabling two channels with the same address but you lose the ability to bridge two secondary channels together (like if a second master sat on a secondary channel and wanted to talk to a slave on one of the other channels.) This means you need to consider which type of switch/multiplexer you need you your system. You may want a single channel option or may want the ability to do multiple channels.

Also, please note that I did make an update to the TCA9544A datasheet to make the single channel enable more clear but the PCA9544A needs to be rewritten. I have put in a ticket in our internal system to update the datasheet since you pointed this out. It should be more specific when stating it can only enable one channel at a time.

Thanks for your question!

If anything is unclear or you have further questions let me know.

-Bobby