When looking for an I3C analog switch / multiplexer it's important to understand some of the specifications of the I3C standard:
- 2-wire push-pull protocol
- Voltage Levels: 1.2V, 1.8V and 3.3V
- Frequency*: 12.5MHz max clock.
- Max Bus Capacitance: 50pF max
*Not to be confused with data rate which may vary (see [FAQ] How do I Select the Right Analog Switch/Multiplexer Bandwidth Based on the Data Rate of my Protocol?)
With the above knowledge and keeping in mind that I3C is a 2-wire push-pull, the following are 4 key specifications for your analog switch / multiplexer that will help pick the correct device for your system:
- The configuration of the analog switch / multiplexer. As stated, I3C is a 2-wire protocol, so a 2 channel device will be needed. To multiplex between two peripheral buses or two controllers, a 2:1 device should be placed between the controller and peripherals. Therefore, a 2 channel 2:1 device would be needed. You aren't limited per se to only 2 peripheral/controllers. As the number of peripherals/controllers increases, so does the configuration, but the channel count will remain the same. (i.e. 4 peripherals would require a 2 channel 4:1).
- The voltage levels of I3C may be 1.2V, 1.8V or 3.3V so it's important to pick a device that can support the I3C levels incorporated in your system.
- The On-capacitance of the analog switch / multiplexer is perhaps the most important spec to take into consideration. The I3C standard specifies a maximum bus capacitance of 50pF. While this allows for some for margin, it's still best to try and minimize the capacitance accumulated from the multiplexer itself. How much room for capacitance the analog switch / multiplexer can add to the system will vary based on the use case but should be taken into consideration when selecting an analog switch / multiplexer for switching I3C signals.
- The bandwidth is typically not going to be a limiting factor here. The I3C clocks runs at 12.5MHz which is a relatively lower frequencies and all of TI's analog switches / multiplexers will be able to support this.
The below table is a recommendation for multiplexers that can pass I3C signals on the data signal paths. These devices are controlled via GPIO. The below is not an exhaustive list of all devices that can support I3C signals. The link provided at the bottom of the table includes more devices that can be used for I2C purposes.
I3C compatible switches for 1 Controller to 2 Peripheral Buses OR 2 Controllers to 1 Peripheral Buses
|I3C Voltage Levels
Supply Voltage Levels
|Body Size (L x W)
|1.8-V compatible control inputs
Supports input voltage beyond supply
|1.8 mm x 1.4 mm
|3.0 mm x 3.0 mm
1.8-V compatible control inputs
|1.8 mm x 1.4 mm