Go to the Impedance Modeler
Cornell Dubilier now offers Spice models of many of its wet aluminum electrolytic capacitors. We have a new online impedance modeling applet that allows the user to select any standard catalog part number among 26 of our most popular series of aluminum electrolytic capacitors. Overview: This applet calculates and interactively charts the typical capacitance, ESR and impedance vs frequency and temperature for 26 of our most popular series of aluminum electrolytic capacitors, from our type MLP and MLS flatpacks to our screw-terminals, to our sturdy three-leaded plug-in style radials to our 9 series of snap-in capacitors
The applet is also able to generate a text-based, pure Spice listing for modeling impedance behavior above 45 ºC where the capacitors are typically used.
First choose the desired type series. The 'CDE Part Number' drop-down list will automatically populate with all available part numbers in order of decreasing voltage followed by decreasing capacitance.
ToolTips display much useful information as the cursor moves over relevant fields on the form. ToolTips also display coordinates on the various chart series.
As soon as a part number is selected the charts of capacitance, ESR and impedance magnitude versus frequency and temperature are displayed. Also displayed are the nominal capacitance, rated voltage, diameter, length, typical ESR and series inductance (ESL). The temperatures which are plotted usually range from -40 ºC to +85 ºC. Certain of our capacitor series above certain voltage thresholds only perform to -25 ºC, and in those cases the plotted series run from -20 ºC to +85 ºC.
There is a slider tool for studying the effect of additional circuit inductance on the impedance. The Ca / Cb radio button denotes 'a'ctual versus 'b'ridge capacitance as discussed in our impedance modeling paper at www.cde.com/resources/technical-papers/impedance.pdf The default selection Ca displays the capacitance without inductive effects, while the Cb selection displays the capacitance with the effects of the ESL plus the interactive slider inductance. The Cb plot will show the resonance effects discussed in the aforementioned technical paper, which manifests as a capacitance that increases with increasing frequency until resonance is reached, where the capacitance is at a singularity, exhibiting a capacitance of positive and negative infinity. Above resonance the capacitor is inductive, resulting in bridge readings of negative capacitance. The chart in this applet only plots positive values of capacitance, and clips the plotted capacitance at about 50% above the nominal capacitance. Still, the effects of resonance are readily apparent. The impedance plot always includes the inductance effects, and is not affected by the Ca/Cb button selection.
Click the Generate Spice Model button for a pop-up window with a text-based, cut-and-pasteable Spice model. The model incorporates RC ladders to simulate the frequency variation of the dielectric oxide resistance as well as the distributed RC ladder behavior of the electrolyte-filled etch tunnels. Due to the limited number of RC stages, the generated Spice model is only valid from 1 Hz to 1 MHz in AC analysis, and from 1 microsecond to 1 second in transient models, and there is a little bit of ripple between the tuning points of the stages. Pure Spice is limited to linear and quadratic temperature coefficients. This ladder behavior with linear and quadratic temperature coefficients is similar to but not identical to the charts displayed in the applet.
Applet Limitations and Cautionary Notes: Note that the Spice model is only valid for warm temperatures, due to limitations of temperature coefficients available to pure Spice models. The plot data is generally most accurate at temperatures of 45 ºC and above, as there is more sensitivity and variation in the cold performance, and the impedance model at the lowest temperature may deviate significantly from actual capacitors. Also note that there is little or no conservatism built into the applet, and the typical ESR is not a maximum ESR limit. For the limits, please refer to our datasheets, catalog listings and life modeling applets.
This applet is only valid for Cornell Dubilier capacitors, as our construction and characteristics are unique. Legal Disclaimer: The CDE Impedance & Spice Modeling Applet is not a contract, license, or authorization of any kind. Specifications and model are subject to change without notice. Cornell Dubilier assumes no liability on accuracy, completeness or suitability for any application.