What's The Difference?!?!

[Jeremy1998]

I would be pulling my hair out over this, if it was long enough...

I am looking on DigiKey for a Sanguino compatible ATMega 644... I know that I need the 644P... There are 3, and all of the specs are EXACTALLY the same!

They are:
ATMEGA644PA-PU
ATMEGA644P-20PQ
ATMEGA644P-20PU

I would guess the ATMEGA644P-20PU, but I'm not sure, so I thought I'd ask...

[keeper63]

I would guess the ATMEGA644P-20PU, but I'm not sure, so I thought I'd ask...

I think that's right - the first one would also be OK likely, but the PA (IIRC) means "automotive temperatures" or something like that (able to survive the extremes of that environment). The PU (once again, IIRC) means "DIP" package, while PQ means the QFP-style package (SMT).

I think.

:-?
[edit]
Hmm - now that I look at Digikey, what I said above likely isn't correct...though I still think the one you are talking about is likely the one needed...[/edit]

[jezuz]

Last digits/letters often define packaging (not package type, but weather it comes in a roll on in a box or whatever) type. If you look closely in the datasheet, the difference will be pointed out somewhere. Generally, this won't make a lick of difference for a hobby user - it's really meant for mass-production companies who require specific methods of setting the IC's into their machines.

The PA might refer to a different temp spec or something of that sort (I know some chips have a military variant that has different temp/pressure/etc standard and have a similar addition in their part number) - but to be sure look over the datasheet. Be smart tho - use cntrl-f to find the specific sections that refer to variations.

//edit

Also, it could be package variations as well. DIP/QFTP - should also be mentioned in the datasheet.

//edit #2

damn you crosh.

[keeper63]

darn you crosh.

Don't be so quick - I am pretty certain I am wrong - check on digikey, lookup ATMega644, then select the filter for DIP - then be confused like I am!

[jezuz]

Well, datasheet says that AU = TQFP; PU = PDIP; MU = VQFN

The A vs PA in the datasheet isn't made clear... I couldn't find it atleast. Probably it's a different of temp ranges or something, b/c the other stats for the two variants seem to be the same.

[Jeremy1998]

The temps are all the same and they are all DIPs. I just need a 644P... Tell me what to get.

[mowcius]

I just need a 644P... Tell me what to get.

ATMEGA644P-20PU

If they're all the same price then you can't go wrong with that one.