The CS5233-3 provides a glitch-free 3.3 V output from one of three possible supplies, (VIN, VSB and 3.3 VAUX). An on-chip linear regulator powers the output when either VIN or VSB is available. Otherwise AuxDrv turns on an external PFET, which connects the 3.3 VAUX supply to the output. The CS5233-3 is intended to provide power to an ASIC on a PCI Network Interface Card (NIC), and meets Intel's "Instantly Available" power requirements which follow from the Advanced Configuration and Power Interface (ACPI) standards. Other applications include desktop computers, power supplies with multiple input sources, and PCMCIA interface cards. The CS5233-3 linear regulator provides a fixed 3.3 V output at up to 1.5 A with an overall accuracy of 2%. The internal NPN - PNP composite pass transistor provides a low dropout voltage and requires less supply current than a straight PNP design. Full protection with both current limit and thermal shutdown is provided. Designed for low reverse current, the IC prevents excessive current from flowing from VOUT to either VIN or ground when the regulator input voltage is lower than the output. The auxiliary drive control feature allows the use of an external PFET to supply power to the output when the regulator supplies are off.