Line driver IC?

T Chap

Hey guys, question for you. I have a remote device that contains a QFN that has 4 outputs on it. Each pin goes high upon sensing some event, so it is not high speed stuff. I need to send the 4 outputs anywhere from 10feet up to maybe 50feet in a rare case. Due to other people being involved in the installation, I was thinking to buffer the QFN part with a line driver IC in case of some wiring problem that might kill the QFN. My thinking is, if a cable gets shorted somewhere, I would rather replace a larger SO chip than the QFN. I am sure that a 4050 would be fine, it has 6 gates and 2 would just be idle with inputs to GND. Does anyone have a better idea for a chip for this roll?

Mike Green

What do you have at the other end? Is it a logic input? You might want some protection there as well. Some kind of Schmitt trigger input on the receiving end would give you a little help with noise. You could use a CD40106 Hex Schmitt Trigger Inverting Buffer and change to using a CD4049 Inverting Buffer as the driver. If you need to slow down the signal transitions for noise reduction, you could just add a little RC filtering on the receive end when you're using a Schmitt trigger input.

T Chap

Thanks Mike for the suggestions. The Prop side will have a PCF8474 reading the inputs from several different remote devices that come in. I think the idea to add the Schmitt Trigger is a good idea to add before the expander to reduce noise.