I need to design a circuitry with at least 16 inputs used to capture low speed digital input signals (such as buttons with dry-contact). I'm also planning to use a multiplexer/demultiplexer (such as 74HC4051-Q100) to save on GPIO-s. Question: if I use a multiplexer with built-in ESD protection, do I still need additional protection on the inputs (opto-isolation or other)?
Please consider that I'd like to avoid the need for multiple dozens of independent components (like 16 x 2 resistors and 16 x 2 diodes, etc. added separately) but I prefer to use fewer components if possible.