Re: Connect I2C devices with different voltage(3.3v & 5v)


"jetq88" <jetq5188@xxxxxxxxx> wrote in message
news:1164728741.262919.166170@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
hi,

Anyone out there has experience to connect I2C devices with diferent
voltages, 3.3v and 5v respectively? I'm working on a project with
MCU(3.3v) to control three devices, one is 3.3v, other two are 5v, I
have trouble to get it work. my question are:
1. can SCL and SDA be connected directly among those devices?
2. should pull up resistors be connected to 3.3v or 5v?
3. do I have to use voltage translator between 3.3v and 5v?
4. should I use series resistors on SCL and SDA, should they be close
to 5v devices or 3.3v devices?

thanks


There's a really simple way to do it using only two MOSFETs. Refer to the
paragraph 18.1 on page 43 of the specification:
http://www.nxp.com/acrobat_download/literature/9398/39340011.pdf



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