Running the Arduino Mega on 3.3 V

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Is it possible to run the Mega on 3.3 Volts by supplying it to the 5V pin?

If so is it possible to program it by attaching a FTDI-cable to the appropriate pins?

The reason for this is that i need to attach several 3.3V peripherals to it.

I know the board works when supplying 3.3 volts, but will putting voltage the wrong way destroy any of the chips on the board and will the TX and RX line work while connected to a USB chip with no power?

/Magnus

2

You can supply it to the Vin or the power connector but you'll be under powering the unit. The voltage regulator on the board is looking a voltage higher then 5V so it can supply a steady 5V the system. You can easily attach 3.3V peripherals to the unit. Thats why it comes with a 3.3V pin for powering those items.

Yes using you can modify a USB cable to exclude the power and only use the data pins and receive your power from an outside source without effecting serial communication.

3

Is it possible to run the Mega on 3.3 Volts by supplying it to the 5V pin?

Not reliably. According to the datasheet, this is outside the "safe operating area".

At 16MHz, the safe operating area stops at 4.5V. Alternatively, the clock speed can be lowered to 8MHz for 2.7V (or maybe 12MHz for 3.3V).

4

If you need to power peripherals using 3.3v can't you simply use the 3.3v output on the board?

5

Thank you Coding Badly. That was valuable information. I have been running the board on 3.3V for some time by supplying the voltage to the 5V pin. So far it is working running on 16MHz, but i will do some tests running with the internal 8MHz resonator instead.

I know that there is a 3.3V pin on the board, but powering peripherals with 3.3V doesn't help when i need to do for example SPI with them.

/Magnus

6

i will do some tests running with the internal 8MHz resonator instead.

This post and the ones that follow should be helpful...
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1264584005/6#6

If you don't want to change the bootloader, this should be helpful to get uploading and monitoring to work...
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1240016311/19#19

I know that there is a 3.3V pin on the board, but powering peripherals with 3.3V doesn't help when i need to do for example SPI with them.

The peripheral may allow 5V. You will have to very carefully read the datasheet to be certain.

Have you considered using a "level shifter" or "level shifting"?