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TCA9548A: I2C voltage translation help

Part Number: TCA9548A

I am designing an audio product that uses I2C with the TCA9548A I2C switch.


I am running the audio circuitry from split supplies,  +2.5v and -2.5v in order to eliminate 256 coupling capacitors that would be needed if I ran the audio off a single  5v supply.


The TCA9548A is also powered by the  +2.5v and -2.5v supply.


The microprocessor that generates the I2C for the TCA9548A MUST run off  5v.


This means that I need a means to shift the 0v/5V I2C signals from the microprocessor to -2.5v/ 2.5v for the TCA9548A.


Can anyone please recommend a part that will accomplish that?

Thanks,

Lukas

  • Hello Lukas,
    I don't understand your system. I2C is a single ended communications protocol and generates it's signals with an open-drain driver. The TCA9548A is a mux of the I2C bus. I am not sure where you are using the -2.5V other than for an amplifier. If the amplifier is I2C controlled than it must be connected to the positive supply. Do you have part numbers that I can look at? A schematic would also be helpful.

    Please try to elaborate on what you are trying to accomplish and with what parts (schematics, block level diagrams, etc). I don't understand your system.
    -Francis Houde
  • Hi Francis,
    The TCA9548A controls a bunch of digital pots, and all these must be referenced to the same power supply, together with the opamps and other audio circuitry, which I decided top power off +-2.5v, which eliminates the need for interstage coupling capacitors, as the audio circuitry can be referenced to ground with a split supply instead of a single +5v supply with 1/2 supply bias for the opamps etc. However the microprocessor must be referenced to the same ground, so runs off +5v. So I needed something to shift the I2C from the microcontroller to the TCA9548A.

    I just found these I2C isolators that will do exactly what I need. www.ti.com/.../iso1540.pdf

    VCC1 can be the microcontroller's +5v, GND1 can be the system ground which is the microcontroller's ground and audio ground, VCC2 can be +2.5v and GND2 can be connected to -2.5v.

    Lukas