Electromagnetic interference and digital circuits: An initial study of clock networks

Radio frequency interference (RFI) can have adverse effects on commercial electronics. Current properties of high-performance integrated circuits (ICs), such as very small feature sizes, high clock frequencies, and reduced voltage levels, increase the susceptibility of these circuits to RFI, causing them to be more prone to smaller RFI levels. Besides, recent developments of mobile devices and wireless networks create a hostile electromagnetic environment for ICs. Therefore, it is important to generalize the susceptibility of ICs to RFI. In this study, we investigate the susceptibility levels and frequency ranges of RFI to the clock network of a digital device, an 8-bit ripple counter, designed and fabricated using AMI 0.5 mu m process technology. Our experimental setup is designed to couple a pulse-modulated RF signal using the direct pin injection method. Our experiments show that relatively low levels of RFI (e. g., 16.8 dBm delivered RF peak power with carrier frequency of 1 GHz) could adversely affect the normal functioning of the device under testing. In the end, SPICE simulations show the sensitivity of a flip-flop, the basic building block of clock network, which further explains the experimental results.