{"id":40525,"date":"2024-10-18T05:00:00","date_gmt":"2024-10-18T10:00:00","guid":{"rendered":"https:\/\/flex.com\/resources\/intermediate-bus-voltage-for-ai-processors"},"modified":"2026-03-19T11:50:44","modified_gmt":"2026-03-19T16:50:44","slug":"intermediate-bus-voltage-for-ai-processors","status":"publish","type":"resource","link":"https:\/\/flex.com\/es\/resources\/intermediate-bus-voltage-for-ai-processors","title":{"rendered":"Voltaje de bus intermedio para procesadores de IA"},"content":{"rendered":"<div id=\"overscroll-top\" style=\"background-color: #eaeef4;\"><\/div>\n<div class=\"resource-header block\">\n\t<div class=\"container\">\n\t\t<div class=\"breadcrumb\">\n\t\t\t<a title=\"Homepage\" href=\"\/\">Flex<\/a>\n\t\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewBox=\"0 0 384 512\"><path d=\"M365.3 256l-22.6 22.6-192 192L128 493.3 82.7 448l22.6-22.6L274.7 256 105.4 86.6 82.7 64 128 18.7l22.6 22.6 192 192L365.3 256z\"\/><\/svg>\n\t\t\t<a title=\"Resources\" href=\"\/resources\">Resources<\/a>\n\t\t\t<svg xmlns=\"http:\/\/www.w3.org\/2000\/svg\" viewBox=\"0 0 384 512\"><path d=\"M365.3 256l-22.6 22.6-192 192L128 493.3 82.7 448l22.6-22.6L274.7 256 105.4 86.6 82.7 64 128 18.7l22.6 22.6 192 192L365.3 256z\"\/><\/svg>\n\t\t\t<a title=\"Intermediate bus voltage for AI processors\">Intermediate bus voltage for AI processors<\/a>\n\t\t<\/div>\n\t\t<h1>Intermediate bus voltage for AI processors<\/h1>\n\t\t\t\t<div class=\"separator\"><\/div>\n\t\t<div class=\"details\">\n\t\t\t\t\t\t\t\t\t<div class=\"date detail\">\n\t\t\t\tPosted on<br>\n\t\t\t\toctubre 18, 2024\t\t\t<\/div>\n\t\t\t\t\t\t<div class=\"categories\">\n\t\t\t\t<div class=\"categories-wrapper\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<span class=\"cat-tag\">Blog<\/span>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"cat-tag\" data-cat-level=\"3\" data-destination=\"https:\/\/flex.com\/industries\/data-center?subcategories=data-center-power#resources\" href=\"https:\/\/flex.com\/industries\/data-center?subcategories=data-center-power#resources\">Data Center Power<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"cat-tag\" data-cat-level=\"3\" data-destination=\"\/industries\/industrial?subcategories=power#resources\" href=\"\/industries\/industrial?subcategories=power#resources\">Power<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<a class=\"cat-tag\" data-cat-level=\"2\" data-destination=\"\/power-modules#resources\" href=\"\/power-modules#resources\">Power Modules<\/a>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t<\/div>\n<\/div>\n\n\n\n<div class=\"sidebar block normal-sidebar\">\n\t<div class=\"container\">\n\t\t<div class=\"content\">\n\t\t\t\n\n<h2 class=\"wp-block-heading has-medium-font-size\" id=\"h-introduction\" style=\"font-style:normal;font-weight:600\">Introduction<\/h2>\n\n\n\n<p>AI is a technology that is rapidly pervading all aspects of society, from face cloning on social media to optimization of factory automation. The remarkable capabilities of AI are driven by significant advances in computing power within server farms, where processor transistor counts now reach hundreds of billions, resulting in chip power dissipation figures measured in kilowatts. However, there are challenges ahead for further progress \u2014 chip supply rails cannot be reduced much more to lower power consumption; heat extraction is a growing issue, and routing over 1,000 amps to a processor chip in the limited space available has become a major practical concern.<\/p>\n\n\n<div id=\"id_69d8f46ee36b3\" class=\"media block\">\n\t<div class=\"container media-center \">\n\t\t<div class=\"media\" style=\"left: 0px; min-width: 100%; max-width: 100%;\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<div class=\"image none\">\n\t\t\t\t\t\t\t<img decoding=\"async\" alt=\"AI chip processor\" src=\"https:\/\/flex.com\/wp-content\/uploads\/2025\/09\/ai-chip-1200x675.jpg\" title=\"\">\n\t\t\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t<\/div>\n\t\n\t<script>\n\t(function () {\n\t\tlet hasRun_id_69d8f46ee36b3 = false;\n\t\tfunction updateVideoDisplay_id_69d8f46ee36b3() {\n\t\t\tconst youtubeVideoId = \"\";\n\t\t\tconst bynderID = \"\";\n\t\t\tconst mediaType = \"image\";\n\t\t\tconst mediaVideoElement = document.getElementById('media-video-id_69d8f46ee36b3');\n\t\t\tconst bodyClass = document.body.className || '';\n\t\t\tconst match = bodyClass.match(\/translatepress-([a-z]{2})(?:_[A-Z]{2})?\/i);\n\t\t\tconst currentLanguage = match ? 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We appreciate your patience and look forward to sharing it with you soon.<\/p>\n\t\t\t\t\t<\/div>\n\t\t\t\t`;\n\t\t\t\tmediaVideoElement.appendChild(errorDiv);\n\t\t\t}\n\t\t}\n\t\t\n\t\tfunction runVideoInjection() {\n\t\t\tif (hasRun_id_69d8f46ee36b3) return;\n\t\t\thasRun_id_69d8f46ee36b3 = true;\n\t\t\tupdateVideoDisplay_id_69d8f46ee36b3();\n\t\t}\n\t\t\n\t\t\/\/ Always run on front-end\n\t\tif (document.readyState === 'loading') {\n\t\t\tdocument.addEventListener('DOMContentLoaded', runVideoInjection);\n\t\t} else {\n\t\t\trunVideoInjection();\n\t\t}\n\t\t\n\t\t\/\/ Also run in editor if available\n\t\tif (typeof wp !== 'undefined' && wp.domReady) {\n\t\t\twp.domReady(runVideoInjection);\n\t\t}\n\t})();\n\t<\/script>\n\t\n\t<script>\n\t\tdocument.addEventListener('DOMContentLoaded', function () {\n\t\t\t\n\t\t\t\/\/ Get the block element by ID\n\t\t\tvar blockElement = document.getElementById(\"id_69d8f46ee36b3\");\n\t\t\tif (!blockElement) return;\n\t\n\t\t\t\/\/ Reveal the block\n\t\t\t(function ($) {\n\t\t\t\tScrollReveal().reveal(blockElement.querySelector(\".container .media\"), {origin: \"bottom\", distance: \"20px\", opacity: 1, duration: 1000});\n\t\t\t\tScrollReveal().reveal(blockElement.querySelector(\".container .content\"), {origin: \"bottom\", distance: \"20px\", opacity: 1, duration: 1000});\n\t\t\t}(jQuery));\n\t\t});\n\t<\/script>\n<\/div>\n\n\t\t<\/div>\n\t\t<div class=\"sidebar normal-column\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t<\/div>\n<\/div>\n\n<div id=\"id-69d8f46f02219\" class=\"box block full-width dark-content es \" style=\"background-color: transparent; background-image: none;\">\n\t<style>\n\t\t#id-69d8f46f02219 > .container > .content {\n\t\t\tbackground-color: transparent;\n\t\t\tposition: relative;\n\t\t\tpadding-top: 48px;\n\t\t\tpadding-right: 0px;\n\t\t\tpadding-bottom: 84px;\n\t\t\tpadding-left: 0px;\n\t\t\tmargin-left: 0px;\n\t\t\tmargin-right: 0px;\n\t\t}\n\t\t@media (max-width: 1272px) {\n\t\t\t#id-69d8f46f02219.box.block.full-width > .container > .content {\n\t\t\t\tpadding-left: 0 !important;\n\t\t\t\tpadding-right: 0 !important;\n\t\t\t\tmargin: 0 !important;\n\t\t\t}\n\t\t}\n\t\t@media (max-width: 960px) {\n\t\t\t#id-69d8f46f02219 > .container > .content {\n\t\t\t\t\/\/padding-top: 24px;\n\t\t\t\tpadding-right: 0px;\n\t\t\t\t\/\/padding-bottom: 42px;\n\t\t\t\tpadding-left: 0px;\n\t\t\t}\n\t\t}\n\t<\/style>\n\t<div class=\"container\">\n\t\t<div class=\"content\">\n\t\t\t\n\n<h2 class=\"wp-block-heading has-medium-font-size\" id=\"h-the-intermediate-bus-approach\" style=\"font-style:normal;font-weight:600\">The intermediate bus approach<\/h2>\n\n\n\n<p>The final chip core voltage, now around 400mV to 900mV, generated from the incoming AC supply to the server farm is done in stages. Initially, it is often converted to 54V<sub>DC<\/sub>, which is practical for distribution around the server rack. This approach enhances electrical safety and keeps currents relatively low, allowing for reasonable cable sizing. DC\/DC converters at the processors can then reduce the voltage directly to sub-1V. However, this large conversion ratio results in significant losses and occupies more real estate, therefore less practical at higher power levels. To address this, an intermediate bus is typically used, followed by a multi-phase Voltage Regulator Module (VRM) located close to the processor to minimize static and dynamic voltage drops under high load currents. A recent power electronics design trend even places this final conversion stage directly beneath the processor to provide \u2018Vertical Power Delivery\u2019.<\/p>\n\n\n\n<p>There is now a choice to be made regarding which intermediate bus voltage to use, and determining the optimal value is not so straightforward as there are multiple factors to consider. The DC\/DC Intermediate Bus Converter (IBC) generating the bus voltage is normally a \u2018fixed ratio\/unregulated\u2019 converter for enhanced efficiency and simplicity. The most common ratios are of 4:1 and 8:1 which produce nominal voltages of 13.5VDC and 6.75VDC, respectively. But how do you decide which to choose?<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\" id=\"h-4-1-or-8-1\" style=\"font-style:normal;font-weight:600\">4:1 or 8:1?<\/h2>\n\n\n\n<p>An obvious key difference between the two bus voltages is the output current rating: around 150A for 6.75V<sub>DC<\/sub> compared with 75A for 13.5V per kW of load. This means a 1<sup>st<\/sup> stage 4:1 IBC can be placed further away from the 2<sup>nd<\/sup> stage VRM converter without considerable distribution loss, freeing up space for processor GPIO, PCIe and memory routing. On the other hand, to avoid significant distribution losses due to 8:1 1<sup>st<\/sup>\nstage IBC they need to be placed near 2<sup>nd<\/sup> Stage VRM which may intervene in processor routing. <\/p>\n\n\n\n<p>An input of 13.5V to the 2<sup>nd<\/sup> stage VRM is often an optimized value for the VRM and produces relatively lower conduction losses in its top-side switch as its duty cycle is lower than with 6.75V input, but the VRM also has relatively higher switching losses. These are proportional to input voltage, switching edge duration, power and frequency, so overall efficiency of the PoL, comparing 13.5V and 6.75V inputs may be little changed. <\/p>\n\n\n\n<p>Perhaps a more significant issue is that a 4:1, 13.5V IBC requires twice the output inductance compared to an 8:1 IBC for the same ripple current and switch off-time (See figure 1 below). The practical result is that for a compact IBC footprint, the inductor, which is already often the tallest component in many designs, will become even taller, potentially increasing the overall height from 5mm to 10mm. This can be problematic close to the processor, where high-power liquid cooling plates extend over adjacent components, requiring them to be low-profile. A 10mm-tall IBC may not fit on the rear side of the PC, restricting placement options.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"\/wp-content\/uploads\/2025\/09\/FPM-Blog-IBC-Voltage-Figure1.jpg\" alt=\"FPM Blog IBC Voltage Figure1\" title=\"\"><\/figure>\n\n\n\n<p class=\"has-text-align-center\"><em>Figure 1: In the output stage of a \u2018ratio\u2019 IBC, inductor size for a given ripple current and off-time is proportional to output voltage<\/em><\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\" style=\"font-style:normal;font-weight:600\">Other considerations<\/h2>\n\n\n\n<p>Of course, other conversion ratios, such as 5:1 and 6:1, are available and can be used to fine-tune performance. However, the more common \u2018standard\u2019 ratios of 4:1 and 8:1 tend to offer the best compatibility and wider range of DC\/DC converter options.<\/p>\n\n\n\n<p>Power conversion architectures are typically evaluated for overall end-to-end efficiency, and this is certainly an important factor when choosing an IBC. However, the actual power dissipated in the IBC and VRM is completely dwarfed by the load, which is typically 25 times larger and located nearby. For example, a processor dissipating 1kW might only cause the IBC to lose 20W. As an illustration, the Flex BMR315 5:1 IBC and <a href=\"https:\/\/flexpowermodules.com\/products\/bmr320\" target=\"_blank\" rel=\"noreferrer noopener nofollow\">BMR320<\/a> 8:1 IBC have only a 0.3% efficiency difference at 400W output, representing just 1.7W difference which is hardly significant. Given the low dissipation in the IBC, it is typically manageable with standard system airflow, rather than needing to be integrated into complex liquid cooling setups required by the latest generation of CPUs.<\/p>\n\n\n\n<h2 class=\"wp-block-heading has-medium-font-size\" style=\"font-style:normal;font-weight:600\">Conclusion<\/h2>\n\n\n\n<p>When selecting the ideal IBC voltage conversion ratio, system designers should consider factors beyond just overall efficiency. Physical size, especially height, may become a deciding factor in the limited space available on today\u2019s high performance AI server boards.<\/p>\n\n\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Los esquemas de conversi\u00f3n de energ\u00eda para procesadores a menudo han priorizado la eficiencia general, pero con la IA aumentando la disipaci\u00f3n de carga en espacios m\u00e1s peque\u00f1os, entran en juego otras limitaciones, como la altura relativa de los convertidores de bus intermedios de diferente relaci\u00f3n.<\/p>","protected":false},"author":18,"featured_media":34152,"template":"","categories":[90,43,97],"tags":[134,257,140],"content-type":[13],"class_list":["post-40525","resource","type-resource","status-publish","has-post-thumbnail","hentry","category-data-center-power","category-power","category-power-modules","tag-bmr314","tag-bmr320","tag-bmr510","content-type-blog"],"acf":[],"_links":{"self":[{"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/resource\/40525","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/resource"}],"about":[{"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/types\/resource"}],"author":[{"embeddable":true,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/users\/18"}],"version-history":[{"count":1,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/resource\/40525\/revisions"}],"predecessor-version":[{"id":40567,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/resource\/40525\/revisions\/40567"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/media\/34152"}],"wp:attachment":[{"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/media?parent=40525"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/categories?post=40525"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/tags?post=40525"},{"taxonomy":"content-type","embeddable":true,"href":"https:\/\/flex.com\/es\/wp-json\/wp\/v2\/content-type?post=40525"}],"curies":[{"name":"gracias","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}