The propagation delay time (t_PD) is measured as the time between an input edge to an output change. This time comprises two parts: an input deglitcher and output slewing delay. The input deglitcher prevents noise on the input pins from affecting the output state. The adjustable slew rate also contributes to the propagation delay time. For the fastest slew-rate setting, the t_PD time is typically 1.5 µs, and for the slowest slew-rate setting, the t_PD time is typically 4.5 µs. For the output to change state during normal operation, one FET must first be turned off.