74AHC125. It's a quad buffer/driver with tri-state that accepts input voltages greater than VCC, so you can power it at 3.3V and feed it 5V and it'll downshift to 3.3V. Of course, it won't shift the 3.3V UP to 5V but many devices will happily accept 3.3V as a high input at 5V- YMMV, check the datasheet, etc etc. Mike H On Sun, Aug 26, 2012 at 9:07 AM, peter green wrote: > I want to take a group of 3.3V logic signals, buffer them and output > them as either 3.3V or 5V logic signals at the board users selection. > > I first thought of using a normal logic chip but I can't seem to find a > family that has 3.3V compatible inputs when running off 5V and is > specced to run off 3.3V and I'd rather users didn't have to swap chips > to change the output voltage. > > I found a chip from TI that can do such conversions, the SN74LVCC3245 > but it seems to have painful power up requirements (according to Ti Vcca > must come up BEFORE vccb). I guess I could put in a RC circuit or > something to slow down the coming up of Vccb but it seems a messy > soloution. > > Any thoughts/advice on this. > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .