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TCA9803: Connecting TCA9803 B side to I2C Mux (Pass-Gate based)

Dror Ben Yehuda
Prodigy 30 points

Part Number: TCA9803
Other Parts Discussed in Thread: PCA9548A, TCA9509

The DS states not to connect B PU on the B-Side because of the internal current source. 

I would like to know if the below connection is problematic (having I2C MUX PCA9548ABS) after the TCA9803

  • +1
    Guru 326430 points

    The PCA9548A is a pass-gate mux; the pull-up resistors of the enabled channels are connected to the TCA9803's B side.
    This is not allowed.

    Exchange the A and B sides, or use a different translator like the TCA9509.

  • 0
    TI__Guru 61061 points

    Hey Dror,

    As Clemens' mentioned, this will be an issue when the PCA9548A drives a low- the internal FET closes (rdson becomes low) and then current flowing from the 4.7k PU will be seen at the TCA9803, which violates IEXT-I. 

    Regards,

    Jack