Radiated immunity of the Gigabit Ethernet Switch embedded in an industrial programmable logic controller

Abstract

In this paper, the immunity of a Gigabit Ethernet Switch (GES) embedded in an industrial Programmable Logic Controller (PLC) is analyzed. For this matter, two configurations are tested. In the first, the GES is mounted on a dedicated test board, which isolates the integrated circuit (IC) with minimum interface components. In the second, the GES is embedded in a commercial PLC product. A Near Field Scan of Immunity setup, based on a local magnetic loop antenna injection is exploited to highlight potential weaknesses of the GES and indentify its sensitive functions. This study showed two susceptible functions in the GES: the oscillator pins and a data bus called Gigabit Media Independent Interface (GMII). These two functions were revealed to be susceptible in two generations of the same integrated circuit. This article also demonstrates the repeatability of the NFS results when the architecture embedding the IC is modified. The modeling of the NFSI and its coupling to the package and clock circuits is also discussed.