I2C (Inter-Integrated Circuit) is a medium-speed digital signalling bus standard.
In terms of stats:
- Two traces
- Up to 3.4 Mbit/s data rate
- Impedance not specified
- Source synchronous clocking
- Serial bus routing topology
- Driver output impedance switches between low and high
Signals are routed from a single driver component to many peripheral components. On the SCL line, it outputs a clock signal and commands are sent on the SDA line:
Some limiting factors:
- The current shouldn’t exceed 3 mA.
- The low logic level is defined from 0 V to 0.4 V.
- The capacitance of all traces/inputs on the peripherals should not exceed 400 pF at the highest data rate.
- There should be at least resistors on the SDA and SCK lines.
- This is to ensure that with typical CMOS voltage levels, we still remain below the current threshold.
- Rise time is given by:
- The bus capacitance means traces shouldn’t be too wide or too long.