Running I2C between 3.3V and 5V PIC controllers

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unni.anad
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2009/08/14 21:49:20 (permalink)
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Running I2C between 3.3V and 5V PIC controllers

Dear all

My new project requires a I2C communication between 3.3V master PIC controller and five 5V pic controller. How I can do it...? 3.3V controller is 18f97j60 and others are 16f877.  Going through the data sheets the 3.3V controller is capable of handling upto 5.5V at I2C pins. If I connect it directly to 5V PIC and used 5V as I2C pullup voltge does it works...? Otherwise I can pull up i2c to 3.3V and run a 3.3bus. Is that ok...? I think the i2c voltage levels with 3.3V and 5V are compatabe. Or whether i should go for level convertors ..

Thanks in advance for your valuable  response
Unnikrishnan K
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    markp
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    RE: Running I2C between 3.3V and 5V PIC controllers 2009/08/15 00:45:02 (permalink)
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    If your 3.3V device is 5V tolerant you should be OK at 5V.

    If you ever need to level shift you can use a pair of N-channel enhancement
    mode MOSFETs. There is a Philips app note for this:
    http://www.standardics.nxp.com/support/documents/i2c/pdf/an97055.pdf

    Mark.
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