Effects of device variations on the EMI potential of high speed digital integrated circuits

Abstract

Radiated emissions from printed circuit boards can be influenced by component variations. This is particularly true for high speed digital circuitry. Changes in resistors, capacitors, inductors, transmission lines, and integrated circuit chips may have a significant effect on the radiation characteristics of a real system. Variations in component characteristics significantly affect digital signal waveforms (risetimes, falltimes, envelope structure). These component variations are routinely accounted for in signal integrity analysis to ensure the purest signal waveshapes. Waveshapes directly influence radiated emission characteristics. Conventional EMC modeling techniques and algorithms do not directly predict the behavior of these devices under temperature, voltage, time, and other variables which affect the operation of the component in question. This paper takes an approach to examining a specific type of component (a CMOS ASIC) and its potential effect on a printed circuit board emissions by analyzing its behavior under certain conditions (e.g. temperature, process variation, and voltage source variation). A high pin count 560 pin Tape Ball Grid Array (TGBA) package is examined. The effects on the IC are bounded and quantified.