Remember, they started out as a digital company. It was only recently that they've had top-notch analog talent (hence the improved ADC specs and various other analog parts). Andy Dan Michaels on 08/23/2000 11:43:45 AM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: (bcc: Andrew Kunz/TDI_NOTES) Subject: Re: [PIC]: Why do 16F877's have 2 sets of VCC & Ground pins? AndyK wrote: >>How about to seperate the VCC to the A/D convertor section? This would reduce >>the vulnerability of the A/D to supply noise and ground bounce problems. > >Have you ever tried it? Run your big PIC with just one power or ground and see >the ADC results fall through the floor. > >The word I got was to treat the one near the ADC section as AVcc and AGND, >because that's essentially what they are. > This is most unfortunate. Exactly the other side of the "AGnd" are the oscillator pins, so this gnd pin makes a really great place to return the little gnd-trace-island that you draw around the xtal/cap/cap area on your pcb to help isolate and confine the hi-freq stuff. So, instead of reducing overall noise, you end up directing it straight into your AGnd. Gakkk. Wrost of all possible worlds. Why on earth would Mchp do this? [a rough guess - no one in the company ever heard of electrons?????????] Hmmmm, confusion, - danM -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics