Andy Kunz wrote: >I want to have a PIC switch it's power supply between 5.5V and 3.5V. Any >ideas? It needs to default to 5.5V on powerup. And it can only use 1 pin. Some questions, Andy. Can you use pin RA4? The problem with your circuit as drawn is that the 470R resistor is gonna be above the PIC supply voltage when you want to operate from 3.3V. Is the 3.3V supply derived from the 5.5V supply? How much current do you actually need at both the 3.3V and 5.5V operation. How much drop can you tolerate? If the whole circuit is operating from a single supply that *changes* from 3.3V to 5.5V, you could just manipulate the Vadj pin on your voltage regulator. This works for both 317 type linear regs as well as LM2575 type switchers. dwayne Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 15 years of Engineering Innovation (1984 - 1999) * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * Do NOT send unsolicited commercial email to this email address. My posting messages to Usenet neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email.