In industrial environments where data transmission is important but difficult due to strong electromagnetic interference and transient overvoltage, digital isolators offer a robust solution. These compact components ensure safe and interference-free communication by galvanically isolating different electrical zones from each other, thus minimizing the effects of environmental interference. The function and structure of a digital isolator and its key specific parameters are explained. In contrast to optocouplers or inductive isolators, digital isolators based on capacitive effects are less susceptible to EMC interference and are, therefore, ideal for harsh industrial conditions. With high data transfer rates and reliable performance, these isolators are particularly effective in applications such as CAN and SPI bus systems, where they maintain system integrity while reducing component complexity.
A specific application is used to show that a powerful, interference-free design can be achieved with minimal effort. The system consists of a transmitter and a receiver, both of which are electrically isolated to ensure reliable signal transmission. The transmitter processes DC voltages of up to ±30 Vmax at the input, while special DC-DC power modules and digital isolators with low parasitic coupling capacitance ensure effective isolation. The signal is transmitted digitally via an unshielded two-wire cable and converted back by the receiver. This enables communication over several hundred meters, even in the presence of electromagnetic interference.
The system is explained using the circuit diagram and layout. The challenges of circuit design in terms of signal integrity, galvanic decoupling, and signal-to-noise ratio are explained. EMC aspects such as interference emission and common mode interference are also discussed, and specific solutions are demonstrated using EMC emission measurement results.
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