Browse Prior Art Database

Bypass Capacitors to Improve Power Distribution on a Fused Card

IP.com Disclosure Number: IPCOM000040524D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 26K

Publishing Venue

IBM

Related People

Diegert, DB: AUTHOR

Abstract

Printed circuit card and board assemblies are often constructed with voltage and ground planes in order to provide low impedance distribution of power to electronic modules mounted on the cards. To maintain this low impedance between the card and the board, a number of card connector pins are assigned to each voltage level and are selected so that they are distributed across the width of the connector. However, some systems require that card current be measured or fused. Constriction of current through a device, such as a fuse, introduces a series inductance into the distribution circuit, which defeats the purpose of using power planes and multiple connector pins. Voltage regulation at the electronic module suffers as a result. The use of bypass capacitors restores a low impedance connection between the card and the board.

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Bypass Capacitors to Improve Power Distribution on a Fused Card

Printed circuit card and board assemblies are often constructed with voltage and ground planes in order to provide low impedance distribution of power to electronic modules mounted on the cards. To maintain this low impedance between the card and the board, a number of card connector pins are assigned to each voltage level and are selected so that they are distributed across the width of the connector. However, some systems require that card current be measured or fused. Constriction of current through a device, such as a fuse, introduces a series inductance into the distribution circuit, which defeats the purpose of using power planes and multiple connector pins. Voltage regulation at the electronic module suffers as a result. The use of bypass capacitors restores a low impedance connection between the card and the board. The circuit is described in the following. As seen in the diagram, a card 1 has card connector pins 2 which are used to distribute voltage to each level of the card 1. Because DC current is blocked by capacitors 3, current must flow through fuse 4 to bridge split power plane 5. However, capacitors 3 allow AC current to flow, and current spreads across the card 1 and connector.

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