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Browse Prior Art Database

POWER MANAGEMENT WITHOUT THE USE OF SEPARATE CONTROL LINES

IP.com Disclosure Number: IPCOM000009719D
Original Publication Date: 2000-Jan-01
Included in the Prior Art Database: 2002-Sep-12
Document File: 3 page(s) / 123K

Publishing Venue

Motorola

Related People

Bill Haber: AUTHOR

Abstract

This paper describes a method of providing power control at the physical level within a digital system, which eliminates the wiring previously required to supply the control signals in traditional systems. The result is a system with simplified interconnect and reduced mass and cost of intercon- nect wiring. This technique was developed for satellite systems, where power control is used exten- sively and weight is at a premium. The approach is suitable for a variety of other applications as well.

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MOTOROLA Technical Developments

8

POWER MANAGEMENT WITHOUT THE USE OF SEPARATE CONTROL LINES

by Bill Haber

ABSTRACT

  This paper describes a method of providing power control at the physical level within a digital system, which eliminates the wiring previously required to supply the control signals in traditional systems. The result is a system with simplified interconnect and reduced mass and cost of intercon- nect wiring. This technique was developed for satellite systems, where power control is used exten- sively and weight is at a premium. The approach is suitable for a variety of other applications as well.

PROBLEMS ENCOUNTERED USING CONVENTIONAL POWER CONTROL

  There are two conventional ways of providing power control as shown in Figure 1. The simplest way uses a separate wire to provide the power con- trol signal. It is the wire, with the associated weight and connection interfaces, which are the disadvan- tage. The second way uses a separate digital inter- face to provide power control for the rest of the module or subsystem. While the control interface may be necessary for other purposes, it is relatively complex (moderate to high power) and can not be powered down with the rest of the circuitry.

PROBLEMS SOLVED BY USING IMPROVED POWER CONTROL

  The improved approach, as shown in Figure 2, uses existing digital interfaces with added function- ality to also provide power control. The power con- trol information either inferred from signal activity or is superimposed on one or more of the digital interfaces which have special drivers and receivers to process the power control information. No addi- tional wires or connector pins are needed to support power control. The power control interface circuits

are low power and only the portion which senses the power information need be powered up when the rest of the equipment is off. For high reliability environments or to assure greater noise immunity, the circuits may be implemented on several of the digital lines and summed.

THEORY OF OPERATION

  There are a variety of ways to implement this approach but they may be separated into two class- es, based on what is sensed to control the power. Either signal activity or an out of range voltage level on the interface may be the item sensed.

  Signal activity relies on either static monitoring or a device like a watchdog timer. Static monitoring employs a low pass filter and sense circuit to detect when the int...