Plenty of good answers, and I'll throw in a "HELL YES" as well.=20

I saw one instance of a product in production using an Atmel AVR, where the=
re is a single pin which is an ADC AREF input only rather than a fully impl=
emented I/O pin.
The application didn't use the ADC at all, and the designer thought he didn=
't need that bypass cap.
There was a box of boards which had failed production test, which had resis=
ted all attempts to repair.=20
I added the specified bypass cap and recovered 100% of those boards.

If the data sheet specifies bypass caps, design them in.  If it doesn't, de=
sign them in anyway, you can always DNP (do not populate) in production.

Bypasses are your friend.  Route them well, and don't skimp.   I use X2Y ca=
ps in critical applications. With any type of bypass cap I route so that po=
wer goes THROUGH the capacitor pad on its way to the chip, and the ground s=
ide of the cap returns directly to the nearest ground pin on the chip. Neve=
r a "tee" where the current has the option to go past the cap.

Similarly with crystal loading capacitors, where I route them directly to t=
he nearest ground pin on the chip and nothing else touches that trace until=
 it joins all the ground pours at the chip ground pin.=20
I have seen boards fail FCC testing hard because crystal caps were "grounde=
d" into a 100 mil ground track that was about a quarter wavelength long at =
400+ MHz.  The "ground" actually worked more like a shunt fed antenna. :-P





--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.