There is quite big variety of AVR microcontrollers that ATMEL company produces. This article is about how to Extract information about AVR microcontroller using its marking on package.
Each microcontroller has its own mark on package: numbers and letters. First is microcontroller type. After follows suffix of three fields.

First field is one or two digits what indicates maximal operation frequency MHz. Second field is a letter showing package type. And third field shows the temperature range of working environment. There are couple more marking letters „L“ and „V“ after microcontroller type. This means that microcontroller operates at low or very low voltages (and frequencies of course).
Table of microcontroller packaging types
| Letter | Package | Lead Pitch (mm) |
|
A |
TQFP |
0.8 |
|
J |
PLCC |
1.27 |
|
M |
MLF |
0.5 |
|
P |
PDIP |
2.54 |
|
S |
SOIC |
1.27 |
|
Y |
SSOP |
0.65 |
There are two types of operating temperature ranges:
| Letter | T, ºC |
|---|---|
|
C |
0…70 |
|
I |
-40…+85 |
And couple examples at the end:
| Marking | VCC, (V) | Fmax, (MHz) | Package |
|---|---|---|---|
|
Attiny15L-1PI |
2.7-5.5 |
1.6 |
8pin PDIP |
|
Atmega64-16AI |
4.5-5.5 |
16 |
64lead TQFP |
|
Atmega325V-8MC |
1.8-5.5 |
8 |
64lead MLF |
|
Attiny2313-20SI |
2.7-5.5 |
20 |
20lead SOIC |
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So what about this one: ATMega644-20AU ?