The SP6231 is a 500mA, 3.3V LDO with an integrated auxiliary voltage input switch. During normal operation, the SP6231 acts as a standard LDO with an output voltage of 3.3V delivering up to 500mA. When the 5V input drops below 4.4V, the 3.3V, VAUX input is switched to the output through an internal PFET, maintaining a constant "glitch free" output voltage. The SP6231 is ideally suited for NIC cards and portable battery powered equipment. When a desktop computer reverts to sleep mode, its 5V bus is removed, leaving only the 3.3V bus. The SP6231's auxiliary output passes the 3.3V bus through, keeping the NIC card available for any Wake-On-LAN command. In battery powered applications, the SP6231 draws power from any available 5V USB connection and reverts to battery power when the USB power is removed. TYPICAL APPLICATION CIRCUIT