Piezoelectric motors are used in digital cameras for autofocus,zooming and optical image stabilization. Theyare relatively small, lightweight and effi cient, but theyalso require a complicated driving scheme. Traditionally,this challenge has been met with the use ofseparatecircuits, including a step-up converter and an oversizedgeneric full-bridge drive IC. The resulting high componentcount and large board space are especially problematicin the design of cameras for ever shrinking cell phones.The LT®3572 solves these problems by combining astep-up regulator and a dual full-bridge driver in a 4mm× 4mm QFN package. Figure 1 shows a typical LT3572Piezo motor drive circuit. A step-up converter is usedto generate 30V from a low voltage power source suchas a Li-Ion battery or any input power source within thepart’s wide input voltage range of 2.7V to 10V. The highoutput voltage of the step-up converter, adjustable upto 40V, is available for the drivers at the VOUT pin. Thedrivers operate in a full-bridge fashion, where the OUTAand OUTB pins are the same polarity as the PWMA andPWMB pins, respectively, and the OUTA and OUTB pinsare inverted from PWMA and PWMB, respectively. Thestep-up converter and both Piezo drivers have their ownshutdown control. Figure 2 shows a typical layout
上傳時間: 2013-11-18
上傳用戶:hulee
Avalanche photo diode (APD) receiver modules arewidely used in fi ber optic communication systems. AnAPD module contains the APD and a signal conditioningamplifi er, but is not completely self contained. It stillrequires signifi cant support circuitry including a highvoltage, low noise power supply and a precision currentmonitor to indicate the signal strength. The challenge issqueezing this support circuitry into applications withlimited board space. The LT®3482 addresses this challengeby integrating a monolithic DC/DC step-up converter andan accurate current monitor. The LT3482 can supportup to a 90V APD bias voltage, and the current monitorprovides better than 10% accuracy over four decades ofdynamic range (250nA to 2.5mA).
上傳時間: 2014-01-18
上傳用戶:wenyuoo
Automotive power systems are unforgiving electronicenvironments. Transients to 90V can occur when thenominal voltage range is 10V to 15V (ISO7637), along withbattery reversal in some cases. It’s fairly straightforwardto build automotive electronics around this system, butincreasingly end users want to operate portable electronics,such as GPS systems or music/video players,and to charge their Li-Ion batteries from the automotivebattery. To do so requires a compact, robust, effi cientand easy-to-design charging system
上傳時間: 2013-11-04
上傳用戶:wfl_yy
The LTC®4155 and LTC4156 are dual multiplexed-inputbattery chargers with PowerPath™ control, featuring I2Cprogrammability and USB On-The-Go for systems suchas tablet PCs and other high power density applications.The LTC4155’s float voltage (VFLOAT) range is optimizedfor Li-Ion batteries, while the LTC4156 is optimized forlithium iron phosphate (LiFePO4)batteries, supportingsystem loads to 4A with up to 3.5A of battery chargecurrent. I2C controls a broad range of functions and USBOn-The-Go functionality is controlled directly from theUSB connector ID pin.
上傳時間: 2013-10-09
上傳用戶:hanhanj
One of the fi rst lessons in a basic electronics coursecovers the symbols for resistors, capacitors, inductors,voltage sources and current sources. Althougheach symbol represents a functional component of areal-world circuit, only some of the symbols have directphysical counterparts. For instance, the three discretepassive devices—resistors, capacitors, inductors—canbe picked off a shelf and placed on a real board muchas their symbolic analogs appear in a basic schematic.Likewise, while voltage sources have no direct 2-terminalanalog, a voltage source can be easily built with an offthe-shelf linear regulator.
上傳時間: 2013-11-24
上傳用戶:simonpeng
Photomultipliers (PMT), avalanche photodiodes (APD),ultrasonic transducers, capacitance microphones, radiationdetectors and similar devices require high voltage,low current bias. Additionally, the high voltage must bepristinely free of noise; well under a millivolt is a commonrequirement with a few hundred microvolts sometimesnecessary. Normally, switching regulator confi gurationscannot achieve this performance level without employingspecial techniques. One aid to achieving low noise is thatload currents rarely exceed 5mA. This freedom permitsoutput fi ltering methods that are usually impractical
上傳時間: 2013-10-28
上傳用戶:lhw888
小電流接地選線裝置的應用在我國10~35kV電網中,普遍采用中性點不接地或經消弧線圈接地的方式,這兩種方式統稱為小電流接地系統。小電流接地系統單相接地故障是電網最常見的故障之一,當發生單相接地故障時,雖然在高壓側發生了故障相電壓降低和非故障相電壓升高,引起中性點位移,但線電壓仍然是對稱的且故障電流小,對供電設備不致造成危害,用戶仍可繼續工作。但單相接地故障有可能發展成為兩相接地短路故障或其他形式的故障,為保證設備及人員安全,應及時找出接地故障線路以便迅速處理。對于單相接地故障的檢測,傳統的方法是采用副二次繞組接成開口三角形的三相電壓互感進行檢測。為了尋找故障線路,值班員通常采取輪流拉閘的辦法來確定具體的故障線路。這種方法,會給安全運行及用戶的生產造成一定的影響,降低了用戶的供電可靠性。隨著微機技術的發展,出現了微機型的小電流接地選線裝置,這種裝置可以在不對線路拉閘停電的情況下找到故障線路,因此與傳統檢測方案相比有很大的優越性。
上傳時間: 2013-12-18
上傳用戶:dddddd55
北京,2007年9月27日——全球有線和無線通信半導體市場的領導者Broadcom(博通)公司(Nasdaq:BRCM)今天宣布,推出全球第一個全功能802.11n單芯片解決方案BCM4322。BCM4322是Broadcom Intensi-fiTM產品系列的最新成員,它不僅是市場上最小和最經濟的802.11n解決方案,而且第一個讓Wi-Fi產品的實際無線吞吐量超過了200Mbps。這款最新的Intensi-fi芯片兼有前所未有的無線性能和很多新功能,擴大了無線覆蓋范圍,使無線網絡能夠兌現802.11n的承諾,即同時支持幾路多媒體應用,包括高清視頻流。
上傳時間: 2014-01-14
上傳用戶:haohaoxuexi
匯編器在微處理器的驗證和應用中舉足輕重,如何設計通用的匯編器一直是研究的熱點之一。本文提出了一種開放式的匯編器系統設計思想,在匯編語言與機器語言間插入中間代碼CMDL(code mapping description language)語言,打破匯編語言與機器語言的直接映射關系,由此建立起一套描述匯編語言與機器語言的開放式映射體系。基于此開放式映射體系開發了一套匯編器系統,具有較高層次上的通用性和可移植性。【關鍵詞】指令集,CMDL,匯編器,開放式 Design of Retargetable Assembler System Liu Ling Feng Wen Nan Wang Ying Chun Jiang An Ping Ji Li Jiu IME of Peking University, 100871【摘要】An assembler plays a very important role in the field of microprocessor verifications and applications, thus how to build a retargetable assembler system has been a hotspot in this field for long time. This paper presents a new method about the retargetable assembler system design.It provides a kind of language CMDL, code mapping description language. During the process of assembling, assembler languages are firstly translated to CMDL, and then mapped to the machine codes. In an other word, CMDL is inserted between assembler languages and machine codes during the translation procedure. As a medium code, CMDL has a lot of features, such as high extraction, strong descript capabilities. It can describe almost all attributes of assembler languages. By breaking the direct mapping relationship between assembler languages and machine codes, the complexities of machine codes are hided to the users, therefore, the new retargetable assembler system has higher retargetable level by converting the mapping from assembler languages and machine codes to assembler languages and CMDL, and implementationof it becomes easier. Based on the new mapping system structure, a retargetable assemblersystem is developed. It proved the whole system has good retargetability and implantability.【關鍵詞】instruction set, symbol table, assembler, lexical analysis, retargetability
上傳時間: 2013-10-10
上傳用戶:meiguiweishi
本文介紹基于 AVR 嵌入系統的三相660 伏電力智能投切開關裝置的開發設計。該裝置以ATmega48V 為核心器件,采用零電壓接通,零電流分斷技術,在投入和切斷瞬間由可控硅承載線路電流,而在正常閉合工作時由電磁接觸器承載電流。可廣泛應用于電力諧波治理和無功補償設備中作為開關部件,具有無沖擊電流、響應時間短等特性。在工礦企業用電設備中存在大量的感性負載,如電弧爐、直流電機調速系統、整流逆變設備等,它們在消耗有功功率的同時,也占用了大量感性無功功率,致使電力功率因數下降。由于無功功率虛占了設備容量、增大了線路的電流值,而線路損耗與電流的平方成正比,因此造成電力資源的巨大浪費。另外,這些感性負載工作時還會產生大量的電力諧波,對電網造成諧波污染,使電能質量惡化,電器儀表工作異常。為了提高功率因數、治理諧波,可以采用動態濾波補償,由電容器和電感器串聯形成消諧回路,起到無功補償和濾除諧波的作用。各種濾波補償系統,基本都由電力電容器、鐵芯電抗器、無功補償控制器和電力投切裝置等構成,其中電力投切裝置負責與電網接通、切斷任務,是整個補償系統中關鍵部件之一。
上傳時間: 2013-10-10
上傳用戶:氣溫達上千萬的