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3.6v i2C part in a 5V uP circuit

Discussion in 'Microcontrollers, Programming and IoT' started by dxpwny, Jul 30, 2015.

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  1. dxpwny


    Jul 9, 2011
    I wish to use a part the has a max vcc of 3.6 volt, and it's i2c bus in a simple 8051 (DS89C450) circuit. I don't know what the exact 3.6v part is yet - it just seems all the parts I've looked at for my application have a max vcc of 3.6v.

    I haven't yet read anything in any datasheet that states that a 3.6v devices i2c bus should work directly with 5V logic. So, I'm wondering .... assuming it's not possible to just throw the parts together, is there a simple circuit I can use to glue to two parts together ?
  2. pgib8


    Jul 26, 2015
    Well the nice thing about I2C is that all the outputs are open-drain / open-collector, meaning they will only ever pull the signal low or leave it floating, but never source anything into it. The lines are pulled high by pull-up resistors. So I'm thinking that you simply pull them high to 3.3V (or what have you) and it should be plenty high enough for your 5V device to recognize them as being high.
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