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TCA9801: “I2C and SMBus/PMBus” vs "I2C"

Kazuhiko Hirano
Genius 14168 points
Part Number: TCA9801
Other Parts Discussed in Thread: TCA9617A

Hello,

TCA9801 datasheet states “intended for I2C bus and SMBus/PMBus systems”.
Some other I2C level shifter devices, for example TCA9617A datasheet states just I2C, does not say PMBus at all. From functional point of view, any differences between “I2C and SMBus/PMBus” and just “I2C” for all TI I2C level shifter devices?

Best regards,

K.Hirano

  • 0
    Guru 300930 points

    SMBus/PMBus define different switching thresholds, but in general, I²C, SMBus and PMBus are compatible with each other on the electrical level.

  • 0 in reply to Clemens Ladisch
    TI__Genius 14168 points

    Clemens,

    Thank you for your response.
    But let me ask some more.
    All TI I2C level shifter devises can be used for both I2C and SMBus/PMBus interface since I²C, SMBus and PMBus are compatible with each other on the electrical level?
    What do you mean SMBus/PMBus define different switching thresholds?
    Please elaborate.

    Best regards,

    K.Hirano

  • 0 in reply to Kazuhiko Hirano
    Guru 300930 points

    SMBus specifies fixed VIL/VIH of 0.8 V/2.1 V. (This is intended to allow mixing 3.3 V and 5 V devices.) I²C specifies these thresholds as 30% × VCC and 70% × VCC. In practice, the actual low/high voltages usually will meet both specification.

  • 0 in reply to Clemens Ladisch
    TI__Genius 14168 points

    Clemens,

    Thank you for your response.
    So, in practice, can you say all TI I2C level shifter devises can be used for both I2C and SMBus/PMBus interface?

    Best regards,

    K.Hirano

  • +1 in reply to Kazuhiko Hirano
    TI__Guru 64210 points

    Kazuhiko Hirano,

    We state our devices are I2C/SMBus compatible meaning we expect them to work in I2C/SMBus systems however that does not mean they are compliant to the I2C/SMBus standards. 

    -Bobby