The TPS748 is designed to operate from an input voltage up to 5.5 V, provided the bias rail is at least 1.62 V higher than the input supply and dropout requirements are met. The bias rail and the input supply must both provide adequate headroom and current for the device to operate normally. Connect a low output impedance power supply directly to the IN pin of the TPS748. This supply must have at least 1 μF of capacitance near the IN pin for optimal performance. A supply with similar requirements must also be connected directly to the bias rail with a separate 1-μF or larger capacitor. If the IN pin is tied to the bias pin, a minimum 4.7 μF of capacitance is needed for performance. To increase the overall PSRR of the solution at higher frequencies, use a pi-filter or ferrite bead before the input capacitor.