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A Method for High Power Systems Boards Using Adjunct Power Boards

IP.com Disclosure Number: IPCOM000010965D
Publication Date: 2003-Feb-05
Document File: 5 page(s) / 52K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses a board-level power delivery system with surface mounted adjunct boards to augment the carry capability of commodity motherboard designs. Benefits include minimizing manufacturing costs.

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A Method for High Power Systems Boards Using Adjunct Power Boards

Disclosed is a method that uses a board-level power delivery system with surface mounted adjunct boards to augment the carry capability of commodity motherboard designs. Benefits include minimizing manufacturing costs.

Background

Maintaining high current in power delivery systems is a major design issue. This can be especially true for 4-layer, 1oz motherboard designs commonly used in the mainstream computer market segment. High current can lead to excessive voltage droops, which may be too difficult for an acceptably-priced voltage regulator (VR) to compensate for. In addition, high current and high resistivity can result in excessive thermal dissipation.�

Currently, a method for dealing with excessive board resistance is to move to thicker copper layers, or increase the total number of layers in the board (see Figure 1).� Implementing 2oz copper, or� increasing the number of board layers from 4 to over 6 can lead to excessive board costs. Another method limits the current draw of future microprocessor designs; however, any such limits may put the microprocessor products at a performance disadvantage.

General Description

The disclosed method is shown in Figure 2. This method uses an adjunct power delivery board that is surface mounted to the motherboard. Both the adjunct and main board have components placed on their upper surfaces. The intent is for power delivery components, such as VRs, to be concentrated on the adjunct board’s surface. In Figure 3, using many solder joint interconnects, this adjunct board’s Vcc and Vss planes are connected in parallel with the motherboard’s Vcc and Vss planes. If both the motherboard and adjunct board have 4 power layers each, 8 layers are achieved without impacting the commodity status of the supplied boards.

The potential impact to the board design is shown in Figure 4.� Each curve in Figure 4 is a line of iso-resistance, required to meet voltage droop specifications at the indicated currents. The x and y values give the VR-socket distance and plane width required to meet the target resistance.� At high currents, such as 250A, the required board plane width quickly becomes very large for even small socket to VR distances. The 150A target, on the other hand, is more reasonable and should be possible on a 4-layer board.� Meanwhile, the 250A target with the adjunct board shows plane dimensions even smaller compared to 150A 4-layer case.� This means that not only are 250A currents be possible with current commodity board manufacturing technology, but also the po...