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TXB0104: Whether the Pull-up resistance need to be the same

Amelie Zheng
Genius 10865 points
Part Number: TXB0104

Hi Team,

May I ask whether the Pull-up resistance need to be the same? res1 need to be equal to res2 or not?

In customer design, 1.8V for CPU and 3.3V for MCU. the pull-up res recommend in CPU and MCU are not the same. 

They are worried whether it may impact the signal quality and make I2C communication fail.

  • 0
    Guru 244030 points

    See section 8.3.5 of the datasheet: the only restriction is that pull-ups must be larger than 50 kΩ.

    Please note that the TXB does not work for I²C, and is unlikely to work with long traces or connectors that increase the total capacitance to more than 70 pF.

    The TXS can be used with I²C, and works with any pull-ups. (But It does not need them because it already has internal pull-ups.)

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24485 points

    Amelie, 

    Yes, Clemens is correct that pullup values (if used) must be large, as the outputs of the device have weak drivers which may not be able to overcome a strong pullup or pulldown.

    Best,
    Michael