On Freitag, 9. März 2007, Dave McGuire wrote: > I'm reading the datasheet for the PIC18F252. On page 259, it > states that the maximum voltage on any pin (with a few exceptions) is > Vdd+0.3V. Later, on page 287, it specifies more specifically that > the maximum voltage for Vref (parameter A21) is also Vdd+0.3V. >
Those are the "absolute maximum ratings", and just mean you won't immediatly destroy your µC when you apply Vdd+0.3V. The Device has clamping diodes to GND and VDD on each pin, so if you go above their Vf, they'll simply start to conduct till the voltage drops or the device burns. Usually those diodes are rated for 10-30mA, so with a high enough series resistor you can use them in your Application (*), but don't count on the ADC working correctly/exact with Vref > Vdd. *) I have an circuit here applying 240V AC directly to an µC pin over a few 100kOhms, providing a nice zero-crossing Interrupt, without any additional protection... /Ernst ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys-and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Sdcc-user mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/sdcc-user
