The PCA9849 is an ultra-low voltage, quad bidirectional translating multiplexer
controlled via the I²C-bus. The SCL/SDA upstream pair fans out to four
downstream pairs, or channels. A single SCx/SDx channel 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 multiplexer 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 PCA9849 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 VDD1 pin is used
to limit the maximum high voltage which is passed by the PCA9849. 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.