Help with ATMEGA variants, please!

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Bawker
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Posted by Bawker: Tue. Aug 23, 2011 - 02:22 AM
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I've been looking at the multitude of various ATMEGA 88/168/328 variants available, trying to figure out what all the suffixes mean, reading datasheets (some of which are undoubtably a little "obsolete")... and I'm still a bit in the dark. Tried searching this forum, but I don't even know how to properly search what I'm after, so here goes.

There are the "plain vanilla" AVR Megas... example:

ATMEGA168-PU

There are "P" variants... example:

ATMEGA168P-PU

I gather that this means "Picopower" device... though I don't understand exactly what makes it "Picopower", and if there's any "downside" to this as opposed to a plain vanilla part.

To further throw confusion into the mix, there are "A" suffixes parts:

ATMEGA168A-PU

and "PA" suffixed parts:

ATMEGA168PA-PU

and "V" suffixed parts:

ATMEGA168V-PU

The "V" parts seem to be only available in slower speed grades, typically 10MHZ max.

Alright... I'm perpetually confused about all of this... Atmel's datasheets lump them all together in one sheet, and expect YOU to somehow decipher all of this, probably by reading an obscure footnote on page 362 or something like that. Ordering information section does NOT help, and device overviews are worthless unless you want to know that "P" means "Picopower" - whatever that means in the real world.

HHHEEELLLLLPPPPPPPP!!!!! :shock:

Can anyone give me a succinct synopsis, with pros/cons of the various types?

Tags:

AVR Microcontrollers, megaAVR and tinyAVR
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DocJC
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Posted by DocJC: Tue. Aug 23, 2011 - 03:10 AM
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I was hoping an expert would answer this for you, but no reply, so I'll give it a go.

Others can correct it if I made a mistake.

The ATmege48/88/168 run at 2.7 - 5.5 V.
The ATmega48V/88V/168V versions run at 1.8 to 5.5 V

Note that the maximum clock speed is dependant upon the operating voltage.

The ATmega48A,PA/88A,PA/168A.PA/328/328P can all run at 1.8 - 5.5 V

Again, the max clock is operating voltage dependant.

The PU suffix relates to the Plastic Dual Inline Package, (PDIP), package, which is useful for prototyping or through hole designs.

I'll let others comment on the other differences, but as a general rule one would go with the newer versions. The older versions are sometimes MORE expensive than the newer, low power, versions.

In spite of all the various versions listed in the Data Sheet, it is sometimes helpful to look at Mouser, or DigiKey, (or your supplier of choice), to see which versions of the chips are actually available. Of course if you are ordering in 1000 chip tapes your Atmel rep will get you whatever you want.

JC

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Bawker
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Posted by Bawker: Tue. Aug 23, 2011 - 03:59 AM
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DocJC,

Thank you! That's a good start...

I figured out all the package suffixes, that's all documented in the "ordering options" sections of the datasheets.

Quick question... if you know... what are the "A" series of parts? Just lower (1.8V) voltage, or is there something else different about them? If not, it seems a bit redundant to have a "V" suffix as well....

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Gold Markclawson
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Posted by clawson: Tue. Aug 23, 2011 - 09:29 AM
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Quote:

Quick question... if you know... what are the "A" series of parts?

I've answered this many times so a search should find a fuller explanation (maybe I should make a tutorial?) but briefly.

Atmel used to make their own chips. I think they were fabbed on something like a 0.35um process. To cut costs they shut their fabs and decided to contract it out to Far Eastern fabs. Those fabs use a more modern technology and are either 0.18um or 0.12um. So the chips they are making are binary compatible but they have lower power requirements (and there's an outside possibility they are more susceptible to noise) so the new chips they are now making have an "A" suffix to differentiate them and most have a non-A to A migration note that explains the electrical characteristics that have changed. With only one exception (I think it might be 324->324A) the 3 signature bytes of the A chips have not been changed which means that operationally they are identical and code built for non-A will simply run as before in the A variant. Only if the datasheet shows that the signature bytes have actually changed should you worry about any operational differences in the chips (and for that there'll be migration note details if you look hard enough).

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Koshchi
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Posted by Koshchi: Tue. Aug 23, 2011 - 03:18 PM
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And this app note will help you with the differences between the regular and P versions.

Regards,
Steve A.

The Board helps those that help themselves.

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Bawker
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Posted by Bawker: Thu. Aug 25, 2011 - 08:12 PM
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So... let me recap, and PLEASE, correct me if I get anything wrong:

(All of this is for the part number suffix before the hyphen, NOT after the hyphen, which denotes packaging options.)

Plain vanilla (no suffix) = original variant parts
"P" in the suffix = "Picopower" low-power parts
"V" in the suffix = Low-voltage, lower clk freq. parts before "A" came along
"A" in the suffix = Newer Fab process, lower voltage, lower power, non-Atmel fabbed parts with possibly more noise on A/D inputs

Only "P" and "A" suffixes can be combined in the same part number.

Is that all correct?

BTW, I noticed that on the ATMega328 parts, there is no "A" suffix... is that because they haven't yet gotten around to "new-fabbing" those parts, or are they such recent parts that they never got the "Original process" treatment and only "New-Fab" parts exist?

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Koshchi
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Posted by Koshchi: Thu. Aug 25, 2011 - 08:29 PM
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Quote:
or are they such recent parts that they never got the "Original process" treatment
I believe that it is this.

Regards,
Steve A.

The Board helps those that help themselves.

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