Whats the difference between ATMEGA168A-PU..

Whats the difference between ATMEGA168A-PU & ATMEGA168-20PU with respect to the arduino? has anyone tried this? Can both be switched?

Are you sure that isn’t a -10PU and not just -PU?

The PU can only go up to 8Mhz at 5v and the 20PU can go up to 20Mhz at 5v.

Heres what i’m referring to…

there is no 20… but the Datasheet for 168A says it can go upto 20mhz… The seller says its a low voltage version and works from 1.8V…

There are minor differences between a 168A and a 168.
In theory, the major difference is a change in process (the actual chip gets smaller, but the circuitry is about the same.) In reality, there may be a couple of other things. For arduino, they should be equivalent. (This is less true of the 168PA)
(The part AFTER the dash is speed rating and package. Otherwise identical.)

So does it really mean it cannot run at 16mhz? which part of the datasheet would clarify on this?

So does it really mean it cannot run at 16mhz?

No. Prior to the 168A, there was a 168-20PU that was spec’ed to run between 2.7 and 5.5V at “up to” 20MHz (linearly derated down to 10MHz at 10MHz, more or less), and there was a 168V-10PU that was spec’ed to run from 1.8 to 2.7V at “up to” 10MHz. This is widely believed to have been a matter of testing. Some fraction of chip would be aimed at the lower voltage range, and tested to make sure they could perform.

With the 168A parts, it seems that there are no longer separate speed ranges. The V has disappeared, the number after the dash has disappeared, and the data sheet contains one nearly linear graph that goes all the way from 1.8V to 5.5V. (This is a consequence of the “shink the chip” process I mentioned before. Smaller chips run faster at lower voltages.)

I’ve ordered a bunch of these… will update once i get them…