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TCA6424A: I/O Voltage Translation

Joel Barker67
Prodigy 10 points
Part Number: TCA6424A

This part states that it's capable of a variety of voltage translations. Are the voltage logic levels programmable through it's configuration registered, or is it dependent on the VCCP and VCCI values? For example, if both VCCP and VCCI are both 3.3V, is it possible to have input voltage levels of 1.8V?

Thank you for your help. 

-Joel Barker

  • 0
    TI__Guru 62910 points
    Hi Joel,

    The levels are not programmable; rather, they scale with the supply voltages provided. The SDC/SCL levels will scale with the VCCI rail, while the P-port voltage levels will scale with the VCCP rail. I hope this helps - please let me know if you have any further questions.

    Regards,
    Max
  • 0
    TI__Mastermind 49370 points
    Hey Joel,

    I believe the voltage translation you are referring to is the input/outputs for the ports are controlled via the Vccp pin.

    "is it dependent on the VCCP and VCCI values?"
    VCCI basically controls the logic levels for the I2C communication while VCCP controls the ports. So if VCCP is set to 5V and you set the port to an output logic high, the port would be around 5V (a little less due to voltage drops) while you could communicate through I2C at 1.8V (VCCI = 1.8V). So yes, it is dependent on the VCCI and VCCP.

    "For example, if both VCCP and VCCI are both 3.3V, is it possible to have input voltage levels of 1.8V?"
    IF VCCI=VCCP=3.3V then ViL would be 30% of Vcc which is about 1V in order to see a logic low. ViH would require the input be 70% of Vcc which is about 2.3V. So if you feed the voltage of 1.8V into SDA/SCL, it would be unknown. If you feed that into the input to a port (set as an input) then I believe this would also be in an unknown state.

    Thanks,
    -Bobby

    BTW: If you have anymore questions feel free to ask.

    Also if your question is actually related to a problem you are trying to solve then giving us more information may help us in trying to find a better solution for you.