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TCA9545A: Question of TCA9545A

Jimmy Lai
Expert 6845 points
Part Number: TCA9545A

Dear Team,

When using the TCA9545A as a level shifter at the same time, if the signal input criterion conflicts with 0.7VCC, how to understand the relationship between Vdpum and Vdpux? Can the former be smaller than the latter? Thanks!
For example, VCC=2.5V, Vdpum=1.8V, Vdpux=3.3V, is the usage restriction required that VCC must be equal to Vdpum, and then Vdpux is greater than Vpass

Many Thanks,

Jimmy

  • 0
    Guru 277020 points

    All five pull-up voltages can be higher than the TCA's supply voltage.

    The easiest way to design a circuit is to supply the TCA with the lowest voltage (1.8 V in your case).

  • 0
    TI__Guru 58120 points

    Hi Jimmy,

    As Clemen's pointed out. Using 1.8V on Vcc for TCA9545A is the easiest answer.

    Figure 17 in the datasheet shows that at around 1.8V on Vpass, the Vcc needs to be 2.7V or less to support 1.8V for level translation. At 2.5V for Vcc, the ViH for SDA/SCL is 1.75V which is just barely satisfied by the 1.8V Vdpum.

    My suggestion aligns with Clemen's suggestion as to just use 1.8V on Vcc to satisfy the level translation requirement and give more margin on the ViH threshold since the RC constant slows down significantly as it approaches Vcc.

    -Bobby