PCA9542

   The PCA9542 is a 1-of-2 bi-directional translating multiplexer,  controlled via the I²C bus. The SCL/SDA upstream pair fans out to two SCx/SDx downstream pairs, or channels. Only one SCx/SDx channel is selected at a time, determined by the contents of the programmable control register. Two interrupt inputs, one for each of the SCx/SDx downstream pair, are provided. One interrupt output, which acts as an AND of the two interrupt inputs, is provided. All I/O pins are 5 V tolerant.

   The pass gates of the multiplexer are constructed such that the V_DDpin of PCA9542 can be used to limit the maximum high voltage which will be passed by the PCA9542. PCA9542 allows the use of different bus voltages on each SCx/SDx pair, so that 3.3 V parts can communicate with 5 V parts without any additional protection. External pull-up resistors can pull the bus up to the desired voltage level for this channel.