{"id":11541,"date":"2025-09-09T11:15:50","date_gmt":"2025-09-09T15:15:50","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/?p=11541"},"modified":"2026-03-27T09:47:43","modified_gmt":"2026-03-27T13:47:43","slug":"how-effective-is-decoupling-capacitance-in-power-distribution-networks","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/2025\/09\/09\/how-effective-is-decoupling-capacitance-in-power-distribution-networks\/","title":{"rendered":"How effective is decoupling capacitance in power distribution networks?"},"content":{"rendered":"\n<p>Modern systems pose many challenges to designers, including signal and power integrity and EMI. The power distribution network (PDN) is especially important as devices can draw immense current leading to unwanted voltage drops at power supply pins, compromising device operation and reliability.<\/p>\n\n\n\n<p>The basic PDN is comprised of several parts. The voltage regulator module (VRM), the discrete decoupling capacitors, the capacitance formed by the power plane cavities, and any decoupling capacitance designed into the die of the devices. Additionally, inductance (mounting and spreading) limits the effectiveness of capacitance over a required frequency range. Finally, dynamic switching currents in modern systems can be large and occupy considerable bandwidth, with these systems relying on capacitance to supply current during these switching events.<\/p>\n\n\n\n<p>We conducted a series of experiments using HyperLynx from Siemens to show the effectiveness of power plane capacitance and how it varies with the dynamic switching characteristics of the load and dielectric constant. This measure of effectiveness is related to the effective radius and is calculated using the following equation.<\/p>\n\n\n\n<figure class=\"wp-block-image aligncenter size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"265\" height=\"127\" src=\"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/65\/2025\/09\/blog-equation.png\" alt=\"\nr=(12*tr)\/(\u221aer)\n\" class=\"wp-image-11542\"\/><\/figure>\n\n\n\n<p>Where:&nbsp;<\/p>\n\n\n\n<p>r= radius in inches&nbsp;<\/p>\n\n\n\n<p>tr= rise\/fall time of switching edge (ns)&nbsp;<\/p>\n\n\n\n<p>er = dielectric constant&nbsp;<\/p>\n\n\n\n<p>The capacitance formed by the power plane cavities depends on the area, the spacing, and the dielectric constant, but its effectiveness depends on the rise \/ fall times of the current demand and the dielectric constant. Both a faster rise \/ fall time (smaller transition time) and an increased dielectric constant shrink the effective area, reducing the capacitance.<\/p>\n\n\n\n<p>There are several cases we considered, including a power plane area that is significantly larger, somewhat larger, or smaller than the effective radius. Additionally, we investigated when to use high dielectric materials or multiple power plane cavity pairs. The following points summarize our findings.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Power Plane Area is significantly larger than the calculated effective area<\/strong> &#8211; High dielectric materials are of minimal impact in noise voltage suppression. Better performance is achieved by increasing capacitance either by minimizing power plane spacing or by increasing the number of plane pairs attached to the current sink.<\/li>\n\n\n\n<li><strong>Power Plane Area is somewhat larger than the calculated effective area<\/strong> &#8211; Further increases in plane area outside of the effective radius \/ area also have minimal impact on performance.<\/li>\n\n\n\n<li><strong>Power Plane Area is smaller than the calculated effective area<\/strong> &#8211; Increasing capacitance by using higher dielectric constant materials can improve noise voltage performance. However, similar, if not better results are achieved by decreasing the spacing or by adding additional plane pairs.\u00a0<\/li>\n<\/ul>\n\n\n\n<p>Download the white paper, <a href=\"https:\/\/resources.sw.siemens.com\/en-US\/white-paper-effective-decoupling-radius\/\" target=\"_blank\" rel=\"noopener\">Effective Decoupling Radius<\/a>, for more details about these experiments and their results.<\/p>\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>The power distribution network (PDN) is especially important as devices can draw immense current leading to unwanted voltage drops at power supply pins, compromising device operation and reliability.<\/p>\n","protected":false},"author":117565,"featured_media":11543,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"spanish_translation":"","french_translation":"","german_translation":"","italian_translation":"","polish_translation":"","japanese_translation":"","chinese_translation":"","footnotes":""},"categories":[12],"tags":[2055,2054,1063,113,2056],"industry":[],"product":[1725],"coauthors":[2057],"class_list":["post-11541","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-learning-resources","tag-decoupling-capacitance","tag-decoupling-capacitance-in-power-distribution-networks","tag-hyperlynx","tag-pcb-design","tag-power-distribution-network","product-hyperlynx"],"featured_image_url":"https:\/\/blogs.sw.siemens.com\/wp-content\/uploads\/sites\/65\/2025\/09\/decoupling-blog.png","_links":{"self":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/11541","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/users\/117565"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/comments?post=11541"}],"version-history":[{"count":1,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/11541\/revisions"}],"predecessor-version":[{"id":11544,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/posts\/11541\/revisions\/11544"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/media\/11543"}],"wp:attachment":[{"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/media?parent=11541"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/categories?post=11541"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/tags?post=11541"},{"taxonomy":"industry","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/industry?post=11541"},{"taxonomy":"product","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/product?post=11541"},{"taxonomy":"author","embeddable":true,"href":"https:\/\/blogs.sw.siemens.com\/electronic-systems-design\/wp-json\/wp\/v2\/coauthors?post=11541"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}