ATMega328P internal oscillator 8MHz and 5V

Hello,

I'm making project with I2C communication and Serial interface(9600 baud) with PC. Right now I'm using internal oscillator of ATMega328p (running with 3.3V power) and serial communication with help of PL2301 module is working working pretty well.
What will happen if I will power it up with 5V? Will it blow or it will also work without problems? I'm also thinking about adding FT234XD chip instead of PL2301 module. Will it work as well?

The ATmega will work fine using the internal oscillator, at 5V power.

The limitation is that at lower voltages, the CPU can't go as fast. Operation at 16 MHz is not guaranteed with 3.3V power.

The ATmega processor at 5 V works just fine with any oscillator speed up to its maximum specified rating. The limitation is that it will not necessarily function at 16 MHz on 3.3 V.

Another concern is whether the internal oscillator will operate sufficiently accurately to provide reliable serial communication.

And there is no advantage in an FTDI chip over a PL2301. FTDI is somewhat “on the nose” regarding past practices in any case.

Then I'll get into more details why I don't want to use external oscillator so maybe You'll help me.

That's my first product I would like to bring to the market and I'm a little worried about passing EMC tests. Thats why I don't want to use external oscillator, since internal one will generate less noise and wll be more immune in noisy enviroment.

Are my worries correct or I should worry at all and add external oscillator?

Paul__B:
The ATmega processor at 5 V works just fine with any oscillator speed up to its maximum specified rating.

And then some. I bought a 24MHz 1284P Pro board from Budvar10 and it works fine.

Kamool:
Then I’ll get into more details why I don’t want to use external oscillator so maybe You’ll help me.

That’s my first product I would like to bring to the market and I’m a little worried about passing EMC tests. Thats why I don’t want to use external oscillator, since internal one will generate less noise and wll be more immune in noisy enviroment.

Are my worries correct or I should worry at all and add external oscillator?

Do Arduino Unos pass that test?

GoForSmoke:
Do Arduino Unos pass that test?

I don't know, I haven't found any info about that. Bt regardins it's sold in Europe then is must comply with directives.

You do know that Arduino is based in Italy?

Yes, I know, but that doesn't really help me (??)

Kamool:
Thats why I don't want to use external oscillator, since internal one will generate less noise and wll be more immune in noisy environment.

What makes you think that?

Actually I've just read 328p datasheet agai ant it was my bad about immunity to noise. It referred to "Low power Crystal Oscillator" (Less immune to noise) and Full Swing Crystal Oscillator" (More immune to noise).

I don't remember where I read about less noise generated by internal oscillator.

Paul__B:
Another concern is whether the internal oscillator will operate sufficiently accurately to provide reliable serial communication.

I have several Atmega328s and Attinys running with their internal 8MHz oscillator and have never had a problem with Serial comms.

...R

But does it work both in 5 deg C and 60 deg C?
I’m planning to use that for motorcycle application.

Kamool:
But does it work both in 5 deg C and 60 deg C?
I'm planning to use that for motorcycle application.

That's simple. You don't need to worry about the temperature - just read the fine print at the end of the datasheet :slight_smile:

Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications.

...R

Robin2:
That's simple. You don't need to worry about the temperature - just read the fine print at the end of the datasheet :slight_smile:

...R

Atmel / Microchip do make a version of the ATMEGA328p called the ATMEGA328P-AUTOMOTIVE.

(but still refer to the same datasheet - with that caveat)).

Hmm...

Thats weird, because I know someone who brought motorcycle onboard computer to the market and got road-homologated.

It used ATMega32A with no problems.

Kamool:
Thats weird, because I know someone who brought motorcycle onboard computer to the market and got road-homologated.

It used ATMega32A with no problems.

They probably had a letter from Atmel.

...R

What do You mean by that?

Kamool:
What do You mean by that?

The piece I quoted in Reply #13 says "Unless specifically provided otherwise,"

Atmel may have written a letter that "specifically provided otherwise"

...R