The TCA9548A device has eight bidirectional translating switches that can be controlledthrough the I2C bus. The SCL/SDA upstream pair fans out to eightdownstream pairs, or channels. Any individual SCn/SDn channel or combination of channels can beselected, determined by the contents of the programmable control register. These downstreamchannels can be used to resolve I2C slave address conflicts. Forexample, if eight identical digital temperature sensors are needed in the application, one sensorcan be connected at each channel: 0-7.
The system master can reset the TCA9548A in the event of a time-out or other improperoperation by asserting a low in the RESET input. Similarly, the power-onreset deselects all channels and initializes the I2C/SMBus statemachine. Asserting RESET causes the same reset and initialization to occurwithout powering down the part. This allows recovery should one of the downstreamI2C buses get stuck in a low state.
The pass gates of the switches are constructed so that the VCC pin can be used to limitthe maximum high voltage, which is passed by the TCA9548A. Limiting the maximum high voltage allowsthe use of different bus voltages on each pair, so that 1.8-V, 2.5-V or 3.3-V parts can communicatewith 5-V parts, without any additional protection. External pullup resistors pull the bus up to thedesired voltage level for each channel. All I/O pins are 5-V tolerant.