The PCA9546A is a quad bidirectional translating switch
controlled via the I2C bus. The SCL/SDA upstream pair fans out to four
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.
An active-low reset (RESET) input allows the PCA9546A to recover
from a situation in which one of the downstream I2C buses is stuck in a
low state. Pulling RESET low resets the I2C state
machine and causes all the channels to be deselected, as does the internal power-on reset
The pass gates of the switches are constructed such that the VCC
pin can be used to limit the maximum high voltage, which will be passed by the PCA9546A. This
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 pull-up resistors pull the
bus up to the desired voltage level for each channel. All I/O pins are 5.5-V tolerant.
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