Project Analog - December 2007 - (Page 18)

Battery-Powered System design considerations Provided by Microchip Technology / Chandler, AZ / www.microchip.com Contents Viewpoint Charging lithium-ion batteries W e have come to expect and require more from our batterypowered equipment. My first Personal Digital Assistant (PDA) would only retain its battery power for a day. If the calendar alarm was enabled, the battery power would quickly go to nothing. Today, my PDA holds its battery charge for an entire week under the same conditions. Both PDAs had the same battery chemistry, Lithium Ion (Li Ion), with the same power density. So what has changed? Simple. The hardware was improved and the power-management techniques were refined. Battery improvements were secondary. PDAs are a great example of where system sophistication is improving rapidly, but as fate would have it, the battery-powered equipment requirements are increasing while battery chemistries remain the same. You 18 · Project AnAlog · dec 07 can accomplish this increase of functionality only if the firmware/software engineers understand the tools available in the microcontroller-based processing unit and if the hardware designers understand the efficiency of the solutions available on the market today. Making analog and digital Play together You can accomplish an improvement in power consumption, and consequently an increase in functionality, if you understand the hardware options and the tools available in microcontrollers. One dimension of power conservation is controlling the magnitude of the power-supply voltage in your application. You are probably interfacing to the real world at some point during your code operation. If you are, you will have analog content in your circuit. Analog power-supply requirements are higher than the requirements for digital. Don’t forget that analognoise margins are much smaller than digital-noise margins. The analog noise floor does not reduce with lower power-supply voltages. It stays the same over power-supply voltage changes. For instance, a 12-bit Analog-to-Digital Converter (ADC) can produce good, solid conversions with a 5V supply. However, that same 12-bit ADC will produce a smaller number of noise free-bits when you use a 2Vsupply. This is because the New trends in battery-powered portable devices Low power design: LDO thermal considerations Analog news Microchip analog page Battery charger overview Sample center microchipDIRECT Reference designs/ app notes Technical training http://www.microchip.com http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/batterychargers http://www.microchip.com/batterychargers http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1469&filter1=function&redirects=appnotes http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1423

Table of Contents Feed for the Digital Edition of Project Analog - December 2007

Project Analog - December 2007 Contents Viewpoint About Project Analog Sponsor4 Charging Lithium-Ion Batteries: System Considerations New Trends In Battery-Powered Portable Devices Low Power Design: LDO Thermal Considerations Runtime Measurements for a Hybrid Power Source Battery-Powered System Design Considerations Analog News—Analog News from Multiple Sources Enter to Win an iPhone Contact Project Analog Sponsor Mindi™ Battery & Power Circuit Simulator Microchip Advanced Parts Selector (MAPS)

Project Analog - December 2007

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