This is a very basic question but I cannot find answer for this. I have a couple of Arduino Nano boards lying with me. With keen scrutinizing I found that a few chips on board where numbered as Atmega 328P-AU 1645 and some were numbered Atmega 328P-AU 1644. Can somebody please tell me the difference the number after AU makes ? I know the difference between an AU and PU chip.


Looks to me like a date code: YYWW, where YY are the last two digits of the year and WW is the ISO week number.

  • I hope it has got nothing to do with functionality and is only a sort of batch number. – skii Jul 4 '17 at 8:22
  • They were made one week apart. That is the only difference. – Majenko Jul 4 '17 at 8:31

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