Estimation of countermeasure effect by a bypass condenser at a source terminal of a CMOS IC

A method for measuring source pin current and an equivalent circuit for the source pin of a CMOS digital integrated circuit are proposed. This equivalent circuit includes the capacitance of the integrated circuit protection diode and the inductance of the lead frame. Using this equivalent circuit, the changes in terminal current that occur when countermeasure components such as a bypass capacitor are inserted can be estimated. The proposed current measurement method was used to verify this equivalent circuit. In addition, the relation between the source pin current and the radiated electromagnetic field was clarified. These results show that this equivalent circuit can be used to estimate the effect of inserting source pin countermeasure components on electromagnetic interference