The LM5051 Low Side OR-ing FET Controller operates in conjunction with an external MOSFET as an ideal diode rectifier when connected in series with a power source. This OR-ing controller allows MOSFETs to replace diode rectifiers in power distribution networks thus reducing both power loss and voltage drops. The LM5051 controller provides gate drive for an external N-Channel MOSFET and a fast response comparator to turn off the FET when current flows in the reverse direction. The LM5051 can connect power supplies ranging from -6V to -100V and can withstand transients up to -100V. The LM5051 also provides a FET test diagnostic mode which allows the system controller to test for shorted MOSFETs.