Project Analog - February 2008 - (Page 5)

Digital Potentiometer Application Circuits and Techniques Contributed by Microchip Technology www.microchip.com mcP41xx/42xx digi Pots Contents Viewpoint Digital potentiometer application circuits Smart ADC architecture Layout techniques for high accuracy and resolution ADCs Analog news The MCP41XX/42XX are volatile/nonvolatile, 7/8-bit digital potentiometers with an SPI interface. These devices offer a variety of configurations simplifying design while minimizing cost, package size and pin count. They offer WiperLock™ Technology, which allows the user unlimited reprogramming and locking of the wiper setting. This is useful for equipment that requires factory trimming or recalibration. The MCP41/42XX families of devices are available with resistor values of 5 KΩ, 10 KΩ, 50k and 100 KΩ. Click here for more information on the MCP41XX/MC42XX family. M any applications require the use of a mechanical trim potentiometer for the calibration of the system to optimize performance. This may be done to calibrate the characteristics of some other component on the board, such as a sensor. Digital potentiometers have many advantages over mechanical trim pots, including higher reliability, less susceptibility to environmental factors such as humidity and vibration, and have lower manufacturing costs since a digital potentiometer does not require manual tuning. Digital potentiometers are a good fit for applications to trim offset and gain in amplifier circuits. In this following circuit, a resistor 5 · ProjeCT ANALog · feb 08 Microchip analog page Mixed-signal overview Sample center microchipDIRECT Reference designs/ app notes Technical training ladder is used to create a voltage window where Pot1 is used to trim the desired offset for the inverting amplifier. A second potentiometer (Pot2) is used in a rheostat mode along with resistor R3 to control the gain of the amplifier. The step resistance of Pot2 relative to resistor R3 determines if the gain trimming is a fine adjustment or a course adjustment. Capacitor C1 is for compensation of the op amp and to inhibit the output from oscillating. http://www.microchip.com http://www.microchip.com http://www.microchip.com/analog http://www.microchip.com/analog http://www.microchip.com/mixedsignal http://sample.microchip.com/Default.aspx?testCookies=true http://www.microchipdirect.com/catalogselection.aspx?returnURL=default.aspx http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11026&mid=11&lang=en&pageId=79 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 for the Digital Edition of Project Analog - February 2008Project Analog - February 2008ContentsViewpointAbout Project Analog SponsorDigital Potentiometer Application Circuits and TechniquesSelecting an Audio Codec for Portable AppsLayout Techniques for High Accuracy and Resolution ADCsSmart ADC ArchitectureThe Number of Bits vs. LSB ErrorsArchitecture Pushes Limits of SAR ADCsAnalog News—Analog News from Multiple SourcesEnter to Win an iPhoneContact Project Analog SponsorTreelinkMicrochip Advanced Parts Selector (MAPS)Project Analog - February 2008Project Analog - February 2008 - Project Analog - February 2008 (Page 1)Project Analog - February 2008 - Contents (Page 2)Project Analog - February 2008 - Viewpoint (Page 3)Project Analog - February 2008 - About Project Analog Sponsor (Page 4)Project Analog - February 2008 - Digital Potentiometer Application Circuits and Techniques (Page 5)Project Analog - February 2008 - Digital Potentiometer Application Circuits and Techniques (Page 6)Project Analog - February 2008 - Digital Potentiometer Application Circuits and Techniques (Page 7)Project Analog - February 2008 - Selecting an Audio Codec for Portable Apps (Page 8)Project Analog - February 2008 - Selecting an Audio Codec for Portable Apps (Page 9)Project Analog - February 2008 - Selecting an Audio Codec for Portable Apps (Page 10)Project Analog - February 2008 - Layout Techniques for High Accuracy and Resolution ADCs (Page 11)Project Analog - February 2008 - Layout Techniques for High Accuracy and Resolution ADCs (Page 12)Project Analog - February 2008 - Layout Techniques for High Accuracy and Resolution ADCs (Page 13)Project Analog - February 2008 - Smart ADC Architecture (Page 14)Project Analog - February 2008 - Smart ADC Architecture (Page 15)Project Analog - February 2008 - Smart ADC Architecture (Page 16)Project Analog - February 2008 - The Number of Bits vs. LSB Errors (Page 17)Project Analog - February 2008 - The Number of Bits vs. LSB Errors (Page 18)Project Analog - February 2008 - Architecture Pushes Limits of SAR ADCs (Page 19)Project Analog - February 2008 - Analog News—Analog News from Multiple Sources (Page 20)Project Analog - February 2008 - Contact Project Analog Sponsor (Page 21)Project Analog - February 2008 - Treelink (Page 22)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 23)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 24)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 25)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 26)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 27)Project Analog - February 2008 - Microchip Advanced Parts Selector (MAPS) (Page 28)http://www.nxtbookMEDIA.com

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