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I2C bus capacitance calculation of PCA9548A connected in chain

Rafi Fridman
Prodigy 20 points
Other Parts Discussed in Thread: PCA9548A, TCA9617B, TCA9517

I would like to use 3 I2C Switch PCA9548A in chain one after the other. Does every switch on the chain serves also as a repeater and the maximum allowed capacitance is 1200pF (400pF at channels of each switch)  or the total maximum allowed capacitance of all together stays 400pF?

  • 0
    TI__Genius 16510 points
    Hello Rafi,
    Thanks for your question!

    The PCA9548A (and our other switches) do NOT buffer the channels. What this means is that total capacitance across the entire bus (including all I2C channels of the switch) is up to 400 pF.

    However, when using multiple switches, we recommend you buffer the signals with a I2C buffer such as the TCA9517 or the TCA9617B. Both of these buffers will allow you isolate capacitance between the two sides to allow for up to 400 pF on either side of the buffer (800 pF total)