We are having a problem with a new part, TMUX4827. The failure mode I am seeing is that when SEL is set to 0, I don’t see our signal pass through the device on S1A to D1. If I set SEL to 1 I can see the other signal come through on S1B to D1. The S1A signal is an RS-232 signal and the signal on S1B is LVCMOS level. The part seems to claim it can support RS-232 levels so I’m not sure why this would be a problem. I can’t probe at pin A1 of the device since it is a BGA, but I can probe the net and see a signal toggling at the pin A1 net, but nothing coming out of pin B1. Do you have any idea what would cause S1A to fail, but S1B to succeed?
Also, how do you determine the orientation of the part? It seems to have a mirror like finish with no clear indicators of any kind on the top that I can see.