Thanks Neil, You are correct, it is about saving space on the layout + routing ease with 2 layers and a TQFP44 PIC24EP512GP806. If it was a through hole part, things would have been easier. My issue is that the decap blocks signal pins and I can't go 0402 package as it is a bit small for my eyes and I don't have the parts either. I went into piclist previous posts and saw that someone helpful had posted a helpful article from AD about decopupling. Article says that a reservoir cap needs to be within 2" of the chip and decaps as close to the chip. I have mine around 50 mils to the PIC but as I said, it blocks signal pins. Regards, Chetan Bhargava http://microz.blogspot.com On Fri, Aug 31, 2012 at 6:55 PM, Neil wrote: > Not sure it's about saving pennies, as I've had the same question > (quandry?) based on PCB space available. Not a definitive answer, but > I've learned that it all depends. In general the closer to the PIC's > power pins the better. At all power pins are better. I've found a > 28-pin PIC driving a handful of 7-seg displays at ~20mA per pin works > nicely with a single 0.1uf cap approx 0.1" away from the pins. Another > app with a PIC only switching on/off a bi-color LED (changing maybe > minutes apart), works fine with a 0.1uf at the power-supply. Also > consider what analog circuitry you'll have and how the digital noise > will affect that. > > Some years ago there was a really nice tutorial on this, with > oscilloscope diagrams showing the noise at various points on the power > rails. It was enlightening to see just how much noise digital I/O's can > generate on the power rail. I'll see if I can find it. > > Cheers, > -Neil. > > > On 8/31/2012 9:31 PM, Dave wrote: >> How lucky do you feel? This is not a simple question. Study the data s= heet and app notes. Why so you seek to save nickels. >> >> Chetan Bhargava wrote: >> >>> As far as I understand, decoupling capacitors should be in closed >>> proximity of power pins of a microcontroller. What is the usual and >>> practical distance that they are put at? >>> >>> Although all the power pins need one cap, I have seen designs with >>> single cap only around 3mm away from a PIC18F6520 non-power pin. Would >>> that be stable given that PIC18F6520 has 4 sets of power pins? >>> >>> Thanks, >>> >>> Chetan Bhargava >>> http://microz.blogspot.com >>> -- >>> http://www.piclist.com PIC/SX FAQ & list archive >>> View/change your membership options at >>> http://mailman.mit.edu/mailman/listinfo/piclist > > -- > 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 .