To this day, Power over Ethernet (PoE) continues to gainpopularity in today’s networking world. The 12.95Wdelivered to the Powered Device (PD) input supplied bythe Power Sourcing Equipment (PSE) is a universal supply.Each PD provides its own DC/DC conversion from anominal 48V supply, thus eliminating the need for a correctvoltage wall adapter. However, higher power devicescan not take advantage of standard PoE Because of itspower limitations, and must rely on a large wall adapteras their primary supply. The new LTC4268-1 breaks thispower barrier by allowing for power of up to 35W for suchpower-hungry 2-pair PoE applications. The LTC4268-1provides a complete solution by integrating a high powerPD interface control with an isolated fl yback controller.
Typical industrial and automotive applications requiremultiple high current, low voltage power supply solutionsto drive everything from disc drives to microprocessors.For many of these applications, particularly thosethat have size constraints, the LT3501® dual step-downconverter is an attractive solution Because it’s compactand inexpensive compared to a 2-chip solution. The dualconverter accommodates a 3V to 25V input voltage rangeand is capable of supplying up to 3A per channel. Thecircuit in Figure 1 produces 3.3V and 1.8V.
Alkaline batteries are convenient Because they’re easy tofi nd and relatively inexpensive, making them the powersource of choice for portable instruments and devicesused for outdoor recreation. Their long shelf life alsomakes them an excellent choice for emergency equipmentthat may see infrequent use but must be ready to go on amoment’s notice. It is important that the DC/DC convertersin portable devices operate over the widest possiblebattery voltage range to extend battery run time, and thussave the user from frequent battery replacement.
Handheld electronic devices play a key role in our everydaylives. Because dependability is paramount, handhelds arecarefully engineered with lightweight power sources forreliable use under normal conditions. But no amount ofcareful engineering can prevent the mistreatment theywill undergo at the hands of humans. For example, whathappens when a factory worker drops a bar code scanner,causing the battery to pop out? Such events areelectronically unpredictable, and important data storedin volatile memory would be lost without some form ofsafety net—namely a short-term power holdup systemthat stores suffi cient energy to supply standby power untilthe battery can be replaced or the data can be stored inpermanent memory.
Specifying the right reference and applying it correctly isa more difficult task than one might first surmise, consideringthat references are only 2- or 3-terminal devices.Although the word “accuracy” is most often spoken inreference to references, it is dangerous to use this wordtoo freely Because it can mean different things to differentpeople. Even more perplexing is the fact that a referenceclassified as a dog in one application is a panacea inanother. This application note will familiarize the readerwith the various aspects of reference “accuracy” andpresent some tips on extracting maximum performancefrom any reference.
Avalanche photodiodes (APDs) are widely utilized in laserbased fiberoptic systems to convert optical data intoelectrical form. The APD is usually packaged with a signalconditioning amplifier in a small module. An APD receivermodule and attendant circuitry appears in Figure 1. TheAPD module (figure right) contains the APD and a transimpedance(e.g., current-to-voltage) amplifier. An opticalport permits interfacing fiberoptic cable to the APD’sphotosensitive portion. The module’s compact constructionfacilitates a direct, low loss connection between theAPD and the amplifier, necessary Because of the extremelyhigh speed data rates involved
Occasionally, we are tasked with designing circuitry for aspecific purpose. The request may have customer originsor it may be an in-house requirement. Alternately, a circuitmay be developed Because its possibility is simply tooattractive to ignore1. Over time, these circuits accumulate,encompassing a wide and useful body of proven capabilities.They also represent substantial effort. These considerationsmake publication an almost obligatory propositionand, as such, a group of circuits is presented here. This isnot the first time we have displayed such wares and, giventhe encouraging reader response, it will not be the last2.Eighteen circuits are included in this latest effort, roughlyarranged in the categories given in this publication’s title.They appear at the next paragraph.
A recent trend in the design of portable devices has beento use ceramic capacitors to filter DC/DC converter inputs.Ceramic capacitors are often chosen Because of theirsmall size, low equivalent series resistance (ESR) and highRMS current capability. Also, recently, designers havebeen looking to ceramic capacitors due to shortages oftantalum capacitors.
生活中許多目標(biāo)的高度和水平距離需要進(jìn)行測量。目前主要的測量方法，仍以傳統(tǒng)的皮尺丈量為主，測量效率不高，有時(shí)還很不方便，沒有技術(shù)成熟的數(shù)字式測高測距產(chǎn)品。以基本的數(shù)學(xué)方法為理論依據(jù)，利用遙控小車做為載體，采用角度傳感器測量角度、霍爾傳感器測量水平距離等，通過單片機(jī)LM3S615進(jìn)行數(shù)據(jù)計(jì)算，實(shí)現(xiàn)了對待測目標(biāo)物體的高度、水平距離等數(shù)據(jù)的快速、精確和數(shù)字式的測量，高度測量精度可達(dá)99.06%，水平測量精度則可達(dá)98.06%。
Abstract: In our lives， the height and horizontal distance of some goals are needed to be measured. Because the currently used methods are still traditional tape-based measuring methods， and the measuring efficiency is low and inconvenient so some kinds of digital and portable measuring methods or instruments are needed. Based on the basic math theory， this paper designed and manufactured a portable， digital and remote controlled measuring mobile small vehicle， which assembled with angle measuring sensor for angle measurement and Hall sensor for horizontal distance measuring. MCU LM3S615 calculated the height and horizontal distance data gotten from these sensors. The measuring process is simple， the measuring results are more accurate and the measuring efficiency is higher than traditional measure instruments. The accuracy of height and distance measurement can reach 99.06% and 98.06%.
單片機(jī)作為一種微型計(jì)算機(jī)，其內(nèi)部具有一定的存儲單元（8031除外），但由于其內(nèi)部存儲單元及端口有限，很多情況下難以滿足實(shí)際需求。為此介紹一種新的擴(kuò)展方法，將數(shù)據(jù)線與地址線合并使用，通過軟件控制的方法實(shí)現(xiàn)數(shù)據(jù)線與地址線功能的分時(shí)轉(zhuǎn)換，數(shù)據(jù)線不僅用于傳送數(shù)據(jù)信號，還可作為地址線、控制線，用于傳送地址信號和控制信號，從而實(shí)現(xiàn)單片機(jī)與存儲器件的有效連接。以單片機(jī)片外256KB數(shù)據(jù)存儲空間的擴(kuò)展為例，通過該擴(kuò)展方法，僅用10個(gè)I/O端口便可實(shí)現(xiàn)，與傳統(tǒng)的擴(kuò)展方法相比，可節(jié)約8個(gè)I/O端口。
Abstract:
As a micro-computer,the SCM internal memory has a certain units(except8031),but Because of its internal storage units and the ports are limited,in many cases it can not meet the actual demand.So we introduced a new extension method,the data line and address lines combined through software-controlled approach to realize the time-conversion functions of data lines and address lines,so the data lines not only transmited data signals,but also served as address lines and control lines to transmit address signals and control signals,in order to achieve an effective connection of microcontroller and memory chips.Take microcontroller chip with256KB of data storage space expansion as example,through this extension method,with only10I/O ports it was achieved,compared with the traditional extension methods,this method saves8I/O ports.
