The MC33566 Low Dropout Regulator is designed for computer peripheral card applications complying with the instantly available requirementsas specified by ACPI objectives. The MC33566 permits glitch–free transitions from “sleep” to “active” system modes and has internal logic circuitry to detect whether the system is being powered from the motherboard main 5.0 V power supply or the 3.3 V aux supply. The MC33566 provides a regulated output voltage of 3.3 V via either an internal low dropout 5.0 V–to–3.3 V voltage regulator or an external P–channel MOSFET, depending on the operating status of the system in which the card is installed. During normal operating mode (5.0 V main supply available) the 3.3 V output is provided from the internal low dropout regulator at an output current of 0.4 A. When the motherboard enters sleep mode, the MC33566 operates from the 3.3 V aux supply and routes the aux current to the output via the external P–channel MOSFET bypass transistor controlled by the drive outpin. As a result, the output voltage provided to the peripheral card remains constant at 3.3 V even during host systems transitions to and from sleep mode.

MC33566 Features:
•Output Current up to 0.4 A
•Excellent Line and Load Regulation
•Low Dropout Voltage
•Prevents Reverse Current Flow During Sleep Mode
•Glitch–Free Transfer from Sleep Mode to Active Mode
•Compatible with Instantly Available PC Systems