Segmented Voltage Regulator Modules (VRM) as a Solution for CPU Core Voltage


The PC industry continues to move closer to the goal of having DC/DC converters that deliver up to 150–200 Amp at 0.95V in the near future. This goal may be an achievable one if engineers carefully consider all of the loss mechanisms, especially loss mechanisms are that most pronounced at high currents such as 30A to 40A per phase. As a step in moving closer to this goal, we have developed a segmented VRM in the form of several modules with each one being capable of delivering up to 40 Amps per phase at efficiency over 80%. With a five phase design, DC/DC converters could deliver 200 Amps. This approach divides a multi-phase DC-DC converter into the following sections:
1. PWM controller and its associated components.
2. Power MOSFETs, MOSFET driver, Output inductor and associated components.
3. Input and output capacitors bank comprising ceramic and electrolytic type.

This application note will address only point (2) above i.e., the power train. The selection of the controller and the output and input capacitors is fairly standard and may be found inthe technical publications. For each phase, the components on point (2) above which constitute all the power components are placed on a small plug-in board of 1.15″ x 0.85″ that delivers 40 Amps and receives the PWM TTL signal from the controller. This module has a footprint of about 0.85″ x 0.25″ of the motherboard space and may be placed anywhere on the board as close as possible to theCPU reducing the transmission impedance and losses and giving the Motherboard designer the flexibility to optimize the power and PCB space utilization. Each modular board may be fitted individually with its own heat sink.–article quote

Another topics discussed inside the application note including the design approach, component selection, layout approach, thermal management, efficiency, conclusion, and the references.

Source :  Alan Elbanhawy (Faichild Semiconductor)

Synchronous Buck Converter showing parasitic inductances circuit

Synchronous Buck Converter showing parasitic inductances circuit

Find more details about the Segmented VRM from the Fairchild Semiconductor by downloading the pdf document from the following source:

Segmented Voltage Regulator Modules (VRM) as a Solution for CPU Core Voltage DOWNLOAD


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