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TS5A3159: Can the device be used as I2C MUX?

Frank Xiao
Genius 12055 points
Part Number: TS5A3159
Other Parts Discussed in Thread: TMUX136

Hi team,

Can the device be used as I2C MUX? When my customer use the device, COM is connected to master, No to the slave, NC float. IN is the control signal. 

We find when select the NC, COM pull to 1.5v, when select NO, COM is pulled to 1.5 V too. The VCC is 3.3v, the IN is 3.3v.

We want to check why the COM pin is 1.5v. Thanks.

  • 0
    TI__Mastermind 45575 points
    Frank,

    Yes, the TS5A3159 may be used as an I2C mux.

    However, I2C is a two bit protocol so most customers use a 2-channel 2:1 switch like the TMUX136 instead of a 1-channel 2:1 switch like the TS5A3159.

    Also the I2C masters and slave use open drain communication. You will need to place pull up resistors on each side of the switch so that the bus can see a logic high voltage when the signal switch is Hi-Z.

    When sizing the resistor pull ups on both sides of the switch remember the pull ups will be in parallel when the signal switch path is low impedance.

    The diagram above shows TS5A3159 correctly supplied with Vcc = 3.3 V which will allow up to a 3.3 V signal to pass through from the COM to NO/NC. If the control logic pin (IN) is set to logic high 3.3 V, then the COM pin will be connected to NO pin based on the switches truth table.

    From the diagram above there is not enough information to know what voltage will be on the COM and NO pin. The voltage on these pins will be based on the rest of the system driving the COM and NO pin. The TS5A3159 is a passive FET switch and doesn't have any source or sink capability.

    I would recommend trying a 2-channel device like the new TMUX136 for I2C switching.

    Thank you,
    Adam