Passive Device Modeling

There are three model types in order to simulate the behavior of passive two-pin devices:

• First order high frequency topologies

• Touchstone models (S-Parameter data)

• SPICE subcircuits

First order high frequency modeling

The simplest approach in modeling passive devices is the first order high frequency modeling. This means, the actual device will get modeled by its nominal value only. In addition to the nominal value, the first order parasitic elements are accounted for as well. There are three basic 2-pin circuit topologies:

Capacitor / C-HF  

First order high frequency model for a capacitor:

• C (Capacitance): nominal capacitance value

• R (Parasitic Resistance, ESR): value of the parasitic resistance

• L (Parasitic Inductance, ESL): value of the parasitic inductance

Resistor / R-HF

First order high frequency model for a resistor:

• R (Resistance): nominal resistance value

• L (Parasitic Inductance): value of the parasitic inductance

• C (Parasitic Capacitance): value of the parasitic capacitance

Inductor / L-HF

First order high frequency model for an inductor:

• L (Inductance): nominal inductance value

• R (Parasitic Resistance): value of the parasitic resistance

• C (Parasitic Capacitance): value of the parasitic capacitance

Handling of multi-pin devices

All kind of models (first order high frequency, Touchstone, SPICE subcircuits)  can be applied to multi-pin devices as well as long as the number of pins is an even number. The general pin numbering rule for a multi-pin device is shown in the figure below:

If a model has to be  assigned to such a N-pin device (with N = 2*m, m is an integer number) the basic 2-pin model is applied according to the following rule:

i = 0;

repeat while i < m {

generate 2-pin model between pin i+1 and pin N-i

i = i+1

}

If a first order capacitor model was assigned to the 8-pin device from above the resulting model would look like in the figure below: