Running attinyat 3.3v?

hello If it possible to run a attiny85 at the same speed as if it was on 5v if i put it on 3.3v? The reason why I'm asking if because I would like to connect a esp D1 mini to the attiny85. I'm just wondering if this is possible?


By speed, do you mean clock frequency?

Yes sorry.


The data sheet explains what clock frequencies can reliably be used at different battery voltages. See Figure 21-1 and 21-2 for the two different speed grades.

This screen shot is from the data sheet.

That is from

It depends on if your attiny85 has a V on the end.

ATTINY85-20SU Is the one I have


Here's the data sheet:

Yes and No! It depends on the clock source you are using when running at 5V. You say you have the 20MHz part, so figure 21-2 in the datasheet applies to your device.

If you are running at 20MHz from 5V, then that would be out of spec when running from 3V3. However, if you are using the internal 8MHz clock source, then that's ok for both 5V and 3V3 operation.

Hey markd833, So you can not run the full 20mhz clock at 3.3v it needs to be at 5v?


Correct. This is figure 21-2 from the datasheet:

As you can see, if you are going to use 20MHz, then correct operation is not guaranteed by the manufacturer below 4V5.

Having said that, there are 328P based boards using a 16MHz crystal running at 3V3 (i.e. outside the manufacturer spec) that seem to work just fine.

You could try your Tiny85 at 20MHz on 3V3 and see what happens, but looking at fig 21-2, I think 3V3 equates to around 13.3MHz. So trying 20MHz might be too big an ask.

Hey markd833, Thank you. I was just wondering. Sense the esp is 3.3v logic level I thought running the attiny85 at that voltage would be getting the same clock speed. But. I was wrong. So I need downshift the logic level in order for it to be correct and run it at the full clock speed. It is something I never done before this is new to me.


Why do you need to run at 20 Mhz?

And why would you connect an ESP to an ATtiny? :worried:

I wanted to try something before I haven't an attiny85 and a esp8266. I wanted to try it out.


Well Running it at it's full speed is always a good thing. I don't think it needs to be at it's full speed But I wanted figure out what I need to make it run at it's full speed. And Having the logic level shifting Seems is what I need.