DESCRIPTION
The PCA9540 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.
The pass gates of the multiplexer are constructed such that the VDD pin can be used to limit the maximum high voltage which will be passed by the PCA9540. This 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.

FEATURES
• 1-of-2 bi-directional translating multiplexer
• Channel selection via I2C bus
• Operating supply voltage 2.5 to 3.6 V
• Operating temperature range 0°C to 70°C
• Power-up with all multiplexer channels deselected
• Low on resistance