Four-Channel Ultra-Low Voltage, Fm+ I²C-Bus Switch with Reset

The PCA9846 is an ultra-low voltage, quad bidirectional translating switch controlled via the I²C-bus. The SCL/SDA upstream pair fans out to four downstream pairs, or channels. Any or all SCx/SDx channels can be selected, determined by the programmable control register. This feature allows multiple devices with the same I²C-bus address to reside on the same bus. The switch device can also separate a heavily loaded I²C-bus into separate bus segments, eliminating the need for a bus buffer.

An active LOW reset input allows the PCA9846 to recover from a situation where one of the downstream I²C-buses is stuck in a LOW state. Pulling the RESET pin LOW resets the I²C-bus state machine and deselects all the channels, as does the internal Power-On Reset (POR) function.

The pass gates of the switches are constructed such that the V_DD1 pin is used to limit the maximum high voltage which is passed by the PCA9846. This allows the use of different bus voltages on each channel, so that 0.8 V, 1.8 V, 2.5 V or 3.3 V parts can communicate 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 3.6 V tolerant.