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TCA9803: I2C buffer + impedance change from low to high

Rosario Gandolfo
Intellectual 1690 points
Part Number: TCA9803

Tool/software:

Hi team,

I would have a question regarding the TCA9803.

Would it be possible to use this device as a buffer for 1.8V, but also to change the input impedance from example 2.2k Ohm at the input to 100k Ohm at the output?
Something like this:

It would be important for the end device to see 100k Ohm.

Would this be possible with TCA9803 or do do you have other suggestions in order implement such a solution?

Best regards,

Rosario

  • 0
    Guru 279750 points

    100 kΩ does not really make sense for I²C. What is that device, and what are its specfic requirements?

    (You must not use pull-up resistors on the TCA980x's B side. The TCA980x has current sources at its B-side outputs, and current sources have a very high output impedance; but I'm not sure if that is what you actually want.)

  • 0 in reply to Clemens Ladisch
    TI__Intellectual 1690 points

    Hi Clemens,

    thank you for your answer!
    I understand what you are saying, but is there another part that makes it possible to define the exact impedance at the output?
    In the meantime I will check if we need exactly 100k or if any high impedance is fine. Can you maybe also comment on the impedance at the output of the TCA980x family? What impedances are possible?

    Best regards,

    Rosario

  • 0 in reply to Rosario Gandolfo
    Guru 279750 points

    The TCA9803 does not guarantee any specific impedance; it is designed to work for I²C by sourcing a current of about 3.3 mA.