The CS5231-3 combines a threeterminal linear regulator with circuitry to control an external PFET transistor with the intent of managing two input supplies. A 5V supply powers the regulator while an auxiliary 3.3V supply is controlled by the IC. The design has been optimized to provide a "glitch-free" transition between the two supplies. The CS5231-3 linear regulator provides a fixed 3.3V output @ 500mA with an overall accuracy of 2%. The NPN-PNP composite pass transistor provides a low dropout voltage and requires less supply current than PNP designs. Full protection including current limit and thermal shutdown is provided.