These signals are used to monitor an input voltage for proper range. PG sinks current to GND if UV is below its threshold, OV is above its threshold, or VDD is below the internal UVLO. PG may not be valid when VDD is below the UVLO.
A high input on OV causes GATE to be driven low. UV does not effect the MOSFET operation. This permits OV to be used as an active-high disable.
OV and UV should be connected to ground when not used, and PG may be left open. Multiple PG pins to be wire ORed using a common pull-up resistor.