PCA9306 can be used as a switch to disconnect one side of the device from the main I2C bus. This can be advantageous in multiple situations. One instance of this situation is if there are devices on the I2C bus which only supports fast mode (400 kHz) while other devices on the bus support fast mode plus (1 MHz). An example of this is displayed in Figure 8-3.

Figure 8-3 Example of an I2C bus with multiple supported frequencies

In this situation, if the controller is on the 1 MHz side then communicating at 1 MHz should not be attempted if PCA9306 were enabled. It needs to be disabled for PCA9306 to avoid possibly glitching state machines in devices which were designed to operate correctly at 400 kHz or slower. When PCA9306 is disabled, the controller can communicate with the 1 MHz devices without disturbing the 400 kHz bus. When the PCA9306 is enabled, communication across both sides at 400 kHz is acceptable.