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TMP112 / I2C

Ran Feldman
Intellectual 780 points
Other Parts Discussed in Thread: TMP112

Hi,

I noticed that the TMP112 supports SMBus and 2-Wire Interface. Not I2C. I wanted to ask what should be done, or what shouldnt be done in order that the TMP112 could be added to an existing I2C bus that operates from 3.3V.

Thanks,

Rani

  • 0
    TI__Mastermind 25190 points

    Rani,

    The TMP112 is designed to conform to the SMBus protocol which can be thought of as a more rigorous standard of I2C and is compatible with I2C if and only if a few requirements are met. For example, the logic levels for the two standards are different, SMBus is designed to allow VDDs of 3 to 5 volts and therefore defines logic levels of VIL = .8V and VIH of 2.1V where as I2C is designed for VDDs of 5V +/- 10% and has logic levels defined as VIL = 1.5V and VIH = 3.0V. The takeaway here is that for devices of these two types to communicate, they must be capable of pulling the bus below .8V and above 3V. Also, the SMBus clock frequency is defined from 10kHz to 100kHz where as the I2C clock frequency has a much more broad specification.

    Further differences between the two protocols can be found here: http://en.wikipedia.org/wiki/SMBus