ATTiny -- 5 v. tolerant if operated at 3.3v.?

Other Hardware 3rd Party Boards
1

I am building what amounts to an in-circuit programmer for an ATTiny85, by surrounding the programming-relevant pins with hex buffers that can be set to high impedance. Using these, the tiny will be hooked to the Arduino when being programmed, and hooked to the breadboard when not being programmed.

The question is, suppose I wish to use the tiny in a 3.3v circuit, but I'm programming it from a 5 v. arduino. Will the tiny be tolerant of the 5v. programming, even if it is powered at 3.3 v.?

Thanks in advance for any help.

2

No. However, you could include series resistors to keep the current through the clamping diodes under the limit.

3

Thanks for the answer. Suppose I used the typical little shifter (MOSFET + 2 10K pullups). If I had 5 v. on both sides of the level shifter, I would pass 5 v. signals between the Arduino and the Tiny. If I had the tiny wired at 3.3 v., I would get typical level shifting. No?

4

That is plausible, noting that these level shifters operate in an open-collector mode. You will need to take that into account.

5

The pullups on the 3.3V side of the level shifter should be connected to 3.3V.

6

(open collector? fets don't have collectors, they have drains!)

They care which side is the lower side - but it doesn't matter if it's 5v on both sides, or 5v high side 3.3 on the low side.