We are developing a small engine controller and I need to interface to a couple of external logic level sensors (cam and crank, open collector Hall sensors) and also need to drive an external logic level load (ignition module). Any recommendations on some circuit topologies based on 74xxx parts (or ?) that would provide a "robust" interface to these external devices (tolerant of shorts to BATT or GND).
Using a Schmitt trigger input gate (with a current limiting resistor, along with a couple of clamp diodes) is what comes to mind as a topology for my sensor input needs, but nothing "clean" comes to mind for "robustly" driving a ~ 5mA, 5V logic level, slow speed (20kHz max), remotely located (~ 2m), load.
Any recommendations as to topology or appropriate logic family (74ACxxx?) would be appreciated - Thank you,
