Description

The I²C bus (Inter-Integrated Circuit) is a popular serial communication interface. It is mainly used to connect microcontrollers with peripheral ICs (e.g. sensors or memory). The bus uses one bidirectional data line (SCL) and one clock line (SDA) each. However, the I²C bus is not only used within circuit boards, but is also extended into other areas in many applications with the aid of various connectors and cables. This makes the I²C bus potentially more susceptible to external interference such as ESD, burst and radiated RF disturbances. The goal of this application note is to show the reader a suitable filter and protection circuit that increases the noise immunity of the I²C bus without sacrificing the signal quality of the data and clock lines. For this purpose, simulation models were created in LTspice and a real application was measured to verify the simulation results.

Contents:
•    Basics and specifications I2C bus
•    Selection of filter and overvoltage protection components
•    Simulation with LTspice for a clock frequency of 400 kHz
•    Measurement of a real application with a clock frequency of 400 kHz