The 74AUP1Z125 is a crystal driver with enable, internal resistor and 3-state output. When not in use theENinput can be driven HIGH, putting the device in a low power disable mode with X1 pulled HIGH via RPU, X2 set LOW and Y in the high impedance OFF-state. In disable mode the output Y assumes the high impedance OFF-state. Schmitt trigger action on theENinput makes the circuit tolerant to slower input rise and fall times across the entire VCCrange from 0.8 V to 3.6 V. Schmitt-trigger action at all inputs makes the circuit tolerant of slower input rise and fall times.