Power current model of LSI/IC containing equivalent internal impedance forEMI analysis of digital circuits

This paper investigates a device model of the power current used for an LSI /IC. The model is proposed to analyze the power bus noise in digital circui t boards. This model is defined in the frequency domain and constructed wit h an equivalent internal impedance and an equivalent internal current sourc e. Accordingly, the output current of the model is affected by power bus im pedance, such as the capacitance of bypass capacitors and the parasitic ind uctance of power bus wiring. Therefore, the model is useful for analyzing t he effectiveness of bypass capacitors and power bus wiring. The structure o f equivalent internal impedance for a simple logic IC, such as 74HCXX, can be represented as an RLC series circuit. These parameters are identified by applying the least square method. To demonstrate the validity of the model , an experimental study was conducted. As a result, it was shown that the o utput current of the model corresponds to the measured current under a vari ety of power bus impedance levels within 6 dB.