The PCA9548A is a 8-channel, bidirectional translating I²C switch. The master SCL/SDA signal pair is directed to eight channels of slave devices, SC0/SD0-SC3/SD3. Any individual downstream channel can be selected as well as any combination of the eight channels.

The device offers an active-low RESET input which resets the state machine and allows the PCA9548A to recover if one of the downstream I²C buses get stuck in a low state. The state machine of the device can also be reset by cycling the power supply, V_CC, also known as a power-on reset (POR). Both the RESET function and a POR cause all channels to be deselected.

The connections of the I²C data path are controlled by the same I²C master device that is switched to communicate with multiple I²C slaves. After the successful acknowledgment of the slave address (hardware selectable by A0 and A1 pins), a single 8-bit control register is written to or read from to determine the selected channels.

The PCA9548A may also be used for voltage translation, allowing the use of different bus voltages on each SCn/SDn pair such that 1.8-V, 2.5-V, or 3.3-V parts can communicate with 5-V parts. This is achieved by using external pull-up resistors to pull the bus up to the desired voltage for the master and each slave channel.