Sanity check: P2 without external clock source
JRoark
Posts: 1,215
I think I know the answer to this, but I dont want to be forced to do a respin of this board.
My uderstanding is the P2, just like the P1, can be operated exclusively on the internal RCFAST or RCSLOW clocks without any external clock source whatsoever, correct? And can switch without issue between the internal clocks without risk of lock-up?
I ask this because I have not seen anyone actually do a board like this. Every real world design I have seen so far uses an external source after booting. My application will not be sensitive to clock drift and doesnt need any real speed (except in very short bursts) so I’m inclined to save the parts cost and run sans external clock. Or maybe I’ll put a pair of unpopulated pads as a “just in case”.
Sanity check, please?
Comments
You don't need an external clock. At least, that's my understanding too.
The incremental cost of a crystal is tiny relative to the P2+PCB cost, so certainly allow for a crystal option to 'future proof' things.
If size is an issue, you can get crystals down to 2016 packages easily.
You may have a future use that a crystal is needed for.
Yeah, you can just stay on RCFAST and RCSLOW.
RCFAST is actually very stable against temperature variations, but its value varies a bit from one chip to another
RCSLOW has much greater variation with temperature, but gives really low current consumption