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