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TCA9546A: I2C switch cascade design

Part Number: TCA9546A
Other Parts Discussed in Thread: TCA9803

Hello expert,

May we know if TCA9546A can support below picture design? Customer is wondering about the driving power is enough or not. Thanks a lot!!

1) Could we use 1 output channel to connect to 4 devices? (only 1 I2C switch)

2) Could we use 1 output channel to connect to 4 I2C switch then each switch output to connect to 4 devices? (5 I2C switches)

Best regards,

Ann Lien

  • This device (like other I²C muxes) uses passive switches; it has no drive strength.

    If some device is not capable of driving the capacitance and the current through all pull-up resistors on all enabled bus segments, then you have to insert buffers, e.g., TCA9803.

  • Hello Ladisch,

    Thanks for your reply. So it depends on external driving power(3.3V pull high), right? Thanks!

    Best regards,

    Ann Lien

  • Hi Ann,

    May I ask what the end equipment is?

    Setting up I2C switches in series/parallel have some challenges you need to be aware of.

    You can cascade I2X MUX's/switches in series. The main concern like Clemen's stated is the strength of the I2C controller/Target devices (downstream) to be able to drive the line low (since highs are done passively by the pull up resistors).

    If all of your logic is running off of 3.3V then you should have enough margin on VIL vs VOLs. (Where ViL at 3.3V should be ~1V). You would need to be careful that you don't sink too much current when multiple channels are enabled as this may damage your driver. 

    The other thing you need to make sure is okay is if you have any address conflicts. 


  • Hello Bobby,

    This request is from server. Thanks for your reply. Will discuss with customer, thanks a lot!

    Best regards,

    Ann Lien