Nice idea, if I can find an appropriate reference. It would need to be=20 >4.5V (when supplied from down to 4.8V), Only thing I find in this=20 range is 4.5V with a MAX6107, but I'll avoid Maxim if possible. I do intend to add a 2.5V reference though, and do some math to compare=20 the output and compensate it accordingly. Cheers, -Neil. On 4/12/2012 6:21 PM, Chris Roper wrote: > If you use the PIC to do the ADC it will be susceptible to the same > voltage fluctuations as the DtoA output. > You would need to use a voltage reference chip for accuracy so why not > just power the PIC from a voltage reference and that would govern the > AtoD accuracy. > > On 12 April 2012 22:25, Richard Prosser wrote: >> Hi Neil, >> >> On 13 April 2012 00:26, Neil wrote: >>> What exactly do you mean by "clamping the output"? I actually need 0.5= V >>> to 4.5V output, and Vdd will be 5V. But I was looking for the A/D >>> feedback,etc for accuracy, since the PWM voltage output will be subject >>> to variations in Vdd. >>> >>> Cheers, >>> -Neil. >>> >> Basically I was thinking about a system where the output voltage was >> limited to, say, 4.5V by means of a series resistor& precision zener >> / TL431 etc. This would then be independent of supply voltage but >> subject to any temperature drift in the clamping device. The minimum >> voltage would be close to zero - if you need it to be 0.5V, then you'd >> need to add it in - use an opamp circuit to provide the clamping >> function with a 0.5V offset.? >> >> RP >> >> -- >> 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 .