Jason R. Miller

Frequency-dependent characterization of bulk and ceramic bypass capacitors

Power distribution networks (PDN) use various kinds of capacitors to create the required impedance profile and to suppress noise. The simple model of bypass capacitors is a series R-L-C network with frequency independent parameters. The paper gives measured data for various bulk and ceramic capacitors, showing the extraction procedure and frequency dependent data of all three parameters. Various physical contributors to the frequency dependencies are identified. From low frequencies up to SRF (series resonance frequency), capacitance can drop as much as 60%. Inductance should be measured in a small PCB fixture with planes, vias and pads representing the intended application. The added inductance due to the capacitor body is shown to be fairly independent of via length connecting to the nearest planes.

Simulating complex power-ground plane shapes with variable-size cell SPICE grids

Power and ground planes can be simulated with rectangular uniform SPICE grids, or by analytically evaluating the double series of modal resonances. For nonrectangular shapes, the Transmission Matrix Method (TLM) can be used. For odd shapes, irregular outlines, cutouts and perforations, a variable-size cell grid is shown to be effective and sufficiently accurate. The adaptive grid preserves the static capacitance of the planes, calculates the modal resonances accurately in the presence of cutouts, and can also account for the perforations of planes.

Calculating partial inductance of vias for printed circuit board modeling

A complete derivation of inductance from energy relations is presented, outlining all the key steps and assumptions. Based on this derivation, the concept of partial inductance is reviewed and several useful expressions for partial inductance are presented. The accuracy of these expressions is then evaluated by comparing these formula to 3D field solutions and measurement data of test structures.

Modeling the impact of power/ground via arrays on power delivery

The impact of via arrays on power and ground planes is examined in This work. Measurements of the plane impedance were made on a 8/spl times/8 via array as a function of via pair location. The results from full-wave field solution are compared to measurement data and excellent correlation is obtained. The results show that the impedance and effective inductance is a strong function of location within the array. The lowest impedance and inductance is measured on the array perimeter. A 4 X increase in the impedance and inductance occurs at the array center. By parameterizing the antipad diameter in simulation it is found that the impedance increases sharply when the antipads overlap.