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Original question:

TCA9535 - I2C rise/fall time requirement

TCA9535: TCA9535/4 - I2C rise/fall time requirement

Yusuke Mukuno
Expert 7395 points
Part Number: TCA9535
Other Parts Discussed in Thread: DAC5578

Hi

My customer plan to use I2C Fast mode.

TCA9535 has the specification of minimum value for I2C input fall time. (20 x (Vdd/5.5V))

Customer understood, it is from I2C standard. However, FPGA output signal for I2C was measured around 1nsec.

If they will not conform to the I2C standard, how will TCA9535 work? (this question is regarding just device operation.)

Also, DAC5578(TI) don't have the specification of minimum value for I2C input fall time at Fast mode.

Thanks

Muk

  • 0
    TI__Guru 72931 points

    Hey Muk,

    "If they will not conform to the I2C standard, how will TCA9535 work? (this question is regarding just device operation.)"

    The device should still work. I believe this was only spec'd because of the i2C standard.

    Keep in mind that a fast fall time may cause the signal to undershoot. I would watch to make sure the undershoot does not exceed the absolute maximum rating for the device (-0.5V). You an slow down the fall time by adding a small series resistor in front of the FPGA SDA/SCL as well.

    Thanks,

    -Bobby

  • 0 in reply to BOBBY
    TI__Expert 7395 points
    Bobby-san,

    Thank you for your answer!!