Project Analog - February 2008 - (Page 15) high-Speed benefitS thE mcP3421 battEry fuEl gaugE dEmo board The MCP3421 Battery Fuel Gauge Demo Board demonstrates how to measure the battery voltage and discharging current using the MCP3421. The MCU algorithm calculates the battery fuel being used. This demo board is shipped with a 1.5V AAA non-rechargeable battery. The demo board displays the following parameters: (a) Measured battery voltage (b) Measured battery discharging current (c) Battery Fuel Used (calculated) The MCP3421 Battery Fuel Gauge Demo Board also can charge a single-cell 4.2V Li-Ion battery. This feature, however, is disabled by firmware since the demo kit is shipped to customers with a non-rechargeable 1.5V AAA battery. Other Microchip products that are supported include the MCP73831, MCP1702, and the PIC18F4550. Click here for more information on the MCP3421DM-BFG this is true when one compares a parallel data structure and a serial data structure of like type (a parallel CMOS output stage will tend to have higher available bandwidth than a serial CMOS output stage). Every now and then, technology advances enable a leap forward in serial data structures that allow similar data rates in comparison to the existing parallel data formats 15 · ProjeCT ANALog · feb 08 available. National Semiconductor, the company which defined and introduced Low Voltage Differential Signaling (LVDS), is now using that technology to offer converter technologies with increased converter speed, increased converter resolution, and smaller package sizes by employing LVDSserial data output structures. There are several advantages to employing LVDS high-speed serial data interfaces to transmit data from the ADC to the digital receiver. First and foremost is pin count. In a traditional parallel CMOS output stage, each digital bit requires a dedicated pin. One additional pin is required to convey timing information by providing the “dataready” signal. In using a high-speed serial LVDS interface, two pins are required per signal. The signals of note are data, clock, and an additional timing signal, the frame signal, which indicates the boundary between digital words. Since LVDS requires two pins per signal (a positive and a negative signal), a total of six pins is required, even for a 14-bit converter signal. Using high speed serial interfaces also brings additional benefits. One of the biggest challenges in the board layout stage for most designs is routing the parallel CMOS data lines. The difficulties arise from the sheer number of lines to be routed as well as noise considerations, such as reducing both interference and crosstalk across data lines. Another consideration is limiting the impact these high speed data lines will have on adjacent circuits. By employing a serial data format, only three differential traces need to be routed, greatly simplifying the layout and reducing the amount of board space dedicated to data traces. Finally, the differential nature of LVDS confers noise immunity. The data line itself experiences a great reduction in common mode noise. In addition, the complementary fields generated help to reduce the EMI created by the high speed data and clock traces into other portions of the circuit. This reduced EMI translates into smaller distances required between components in order to minimize crosstalk, resulting in reduced circuitry size. challengeS There’s an old saying: “There’s no such thing as a free lunch.” Nowhere is this truer than in the world of modern electronics. There are challenges raised by the use of high- Contents Viewpoint Digital potentiometer application circuits Smart ADC architecture Layout techniques for high accuracy and resolution ADCs Analog news Microchip analog page Mixed-signal overview Sample center microchipDIRECT Reference designs/ app notes Technical training http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en532698 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/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
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