What is the difference in connecting two crystal capacitors in three situations below (AT90USB162 and other AVRs):
- A: both to GND (this is the solution found in AN and datasheets)
B: both to VCC
C: one to GND and one to VCC?
Since GND and VCC lines conduct same currents and are symmetrical in terms of voltage fluctuations, it seems to me A and B are equivalent and it does not really matter where the crystal quartz capacitors are connected to.
My question is: Why do all ATMEL's (related) application notes and datasheets state it must be GND?
Second question (if nobody could answer the first one other way than "Because.") is: what about method C? Is there any difference?
I will traditionally answer the questions of "Why would you need that?". Simple answer: my PCB layout simplifies greatly if these capacitors could be connected the way I like (and not necessarily to GND)