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EXTENDING BATTERY LIFE FOR SELF-POWERED PC CARDS BY USING MULTIPLE POWER SOURCES

IP.com Disclosure Number: IPCOM000008317D
Original Publication Date: 1997-Sep-01
Included in the Prior Art Database: 2002-Jun-05
Document File: 3 page(s) / 169K

Publishing Venue

Motorola

Related People

Geoff Scotton: AUTHOR

Abstract

A method is presented to extend the battery life of a self-powered PC Card, such as a wireless modem, by matching the power source configuration of the PC Card with the power consumption capabili- ties and demands of the device and host platform.

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MOTOROLA Technical Developments

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EXTENDING BATTERY LIFE FOR SELF-POWERED PC CARDS BY USING MULTIPLE POWER SOURCES

by Geoff Scotton

  A method is presented to extend the battery life of a self-powered PC Card, such as a wireless modem, by matching the power source configuration of the PC Card with the power consumption capabili- ties and demands of the device and host platform.

1 .O INTRODUCTION

  Battery life is an important performance criteria for any self-powered PC Card, and particularly so for a portable wireless modem. For a wireless modem product, user expectations of battery life are conditioned by products such as pagers which exhibit battery life measured in weeks and even months, and cellular telephones which minimally operate in stand-by mode for a full working day. Additionally, users demand minimal product size and weight while still having his/her battery life expectations met.

  While designing a wireless modem for minimal power consumption during active use, it is often necessary to build "power saving" modes of opera- tion that allow the wireless modem to "sleep" for extended periods (several/many seconds) which will extend battery life. Consideration of the power- conservation mode of operation allows the wireless modem product designer to minimize the battery size and weight but may not meet user battery life expectations when used under a heavy usage model.

  In this paper, a method is proposed for optimizing the battery size and capacity of a PC Card wireless modem while meeting the conflicting goals of minimal weight and extended battery life.

2.0 PC CARD POWER SOURCING OPTIONS

Traditionally PC Card (i.e. PCMCIA) devices draw power from the host device using the Vcc,

Vppl and Vpp2 pins of the PC Card interface. Vcc generally provides operating current, minimally to 500 mA at voltages at 3.3V or 5V levels. Vppl and Vpp2 power for specialized functions, typically less than 200 mA at either 5V or 12V. Upon insertion of the card into the host the specific power needs of the device are made known to the host device via the Card Information Structure (CIS). When the card is first recognized and configured by the host, the power needs are determined and made available to the PC Card.

  Typically a PC Card is able to operate entirely using host provided power sources. However when peak current demands exceed current levels that can be sustained by the host device, such as during transmissions for a wireless modem, it is necessary to source the peak current needs directly from the PC Card itself, typically through an on-board battery.

  A self-powered PC Card provides its own power source from an on-board rechargeable or disposable battery. A fully self-powered card is capable of operating in complete absence of power provided at the PC Card interface. However, operat- ing completely from the on-board battery may result in unacceptably short battery life under heavy use with a moderately sized battery, or may require an unwield...