A light-emitting diode (LED) is a semiconductor device that emits narrow-spectrum incoherent light when forward-biased.The color of the emitted light depends on the chemical composition of the semiconductor material used, and can benear-ultraviolet, visible or infrared. LEDs are more prevalent today than ever before, replacing traditional incandescent andfluorescent bulbs in many lighting applications. Incandescents use a heated filament, are subject to breakage and burnoutand operate at a luminous efficiency of 2% to 4%. Fluorescents are more efficient, at 7% to 12%, but require highdrive voltage and contain mercury, a toxic substance that may be eventually banned in certain countries. LEDs, however,produce light directly through electroluminescence, operate at low voltage and can deliver over 20% luminous efficiency.
上傳時(shí)間： 2013-11-07
上傳用戶(hù)：xiaoyuer
PCI ExpressTM is the third generation of PCI (PeripheralComponent Interconnect) technology used to connect I/Operhipheral devices in computer systems. It is intended asa general purpose I/O device interconnect that meets theneeds of a wide variety of computing platforms such asdesktop, mobile, server and communications. It alsospecifies the electrical and mechanical attributes of thebackplane, connectors and removable cards in thesesystems.
上傳時(shí)間： 2013-11-17
上傳用戶(hù)：squershop
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.
上傳時(shí)間： 2014-12-24
上傳用戶(hù)：jasson5678
Handheld designers often grapple with ways to de-bounceand control the on/off pushbutton of portable devices.Traditional de-bounce designs use discrete logic, fl ipflops, resistors and capacitors. Other designs includean onboard microprocessor and discrete comparatorswhich continuously consume battery power. For highvoltage multicell battery applications, a high voltageLDO is needed to drive the low voltage devices. All thisextra circuitry not only increases required board spaceand design complexity, but also drains the battery whenthe handheld device is turned off. Linear Technology addressesthis pushbutton interface challenge with a pairof tiny pushbutton controllers.
標(biāo)簽： 按鍵開(kāi)關(guān) 控制器 系統(tǒng)設(shè)計(jì)
上傳時(shí)間： 2013-11-18
上傳用戶(hù)：ZJX5201314
An essential component of a noise-free audio device isa clean power supply, but few switching regulators canoperate at high efficiency while keeping the switchingfrequency out of the audio band. The LTC®3620 fills thisvoid. It is a high efficiency 15mA buck regulator with aprogrammable minimum switching frequency, making itpossible to virtually eliminate audible switching noise. Theinternal synchronous switches and low quiescent currentof this buck regulator provide the ability to maintain highefficiency, while its small footprint makes it ideal for tiny,low power audio applications.
標(biāo)簽： 超低功率 控制 開(kāi)關(guān)噪聲 方案
上傳時(shí)間： 2013-10-21
上傳用戶(hù)：非衣2016
Telecommunication, satellite links and set-top boxes allrequire tuning a high frequency oscillator. The actualtuning element is a varactor diode, a 2-terminal device thatchanges capacitance as a function of reverse bias voltage.1 The oscillator is part of a frequency synthesizingloop, as detailed in Figure 1. A phase locked loop (PLL)compares a divided down representation of the oscillatorwith a frequency reference. The PLL’s output is levelshifted to provide the high voltage necessary to bias thevaractor, which closes a feedback loop by voltage tuningthe oscillator. This loop forces the voltage controlledoscillator (VCO) to operate at a frequency determined bythe frequency reference and the divider’s division ratio.
標(biāo)簽： 開(kāi)關(guān)穩(wěn)壓器 低噪聲 上傳時(shí)間： 2013-12-20
上傳用戶(hù)：ABCDE
The LTM4601 DC/DC μModule regulator is a completehigh power density stepdown regulator for up to 12Acontinuous (14A peak) loads. The device is housed ina small 15mm ¥ 15mm ¥ 2.8mm LGA surface mountpackage, thus the large power dissipation is a challengein some applications. This thermal application note willprovide guidelines for using the μModule regulator inambient environments with or without air fl ow. Loadcurrent derating curves are provided for several inputvoltages and output voltages versus ambient temperatureand air fl ow.
上傳時(shí)間： 2013-10-19
上傳用戶(hù)：bakdesec
數(shù)字控制的交流調(diào)速系統(tǒng)所選用的微處理器、功率器件及產(chǎn)生PWM波的方法是影響交流調(diào)速系統(tǒng)性能好壞的直接因素。在介紹了正弦脈寬調(diào)制(SPWM)技術(shù)的基礎(chǔ)上，設(shè)計(jì)了一種以8098單片機(jī)作為控制器，以智能功率模塊IPM為開(kāi)關(guān)器件的變頻調(diào)速系統(tǒng)。通過(guò)軟件編程，產(chǎn)生正弦脈沖寬度調(diào)制波形來(lái)控制絕緣柵雙極晶體管的導(dǎo)通和關(guān)斷，從而達(dá)到控制異步電動(dòng)機(jī)轉(zhuǎn)速的目的。實(shí)驗(yàn)結(jié)果表明，該系統(tǒng)可調(diào)頻率調(diào)電壓，穩(wěn)定度高，調(diào)速范圍寬，具有較強(qiáng)的實(shí)用價(jià)值 Abstract: AC variable speed with digital control systems used microprocessors， power devices and generate PWM wave is the direct factors of affecting the performance AC speed regulation system. On the basis of introducing the sinusoidal pulse width modulation (SPWM) technology，this paper designed variable speed system which used 8098 as a controller， intelligent power module IPM as switching device. Through software programming， resulting in sinusoidal pulse width modulation waveform to control the insulated gate bipolar transistor turn on and off， so as to achieve the purpose of speed control of induction motors. Experimental results show that the system can adjust frequency modulation voltage， high stability， wide speed range， has a strong practical value.
標(biāo)簽： 8098 SPWM 單片機(jī) 變頻調(diào)速系統(tǒng)
上傳時(shí)間： 2013-11-14
上傳用戶(hù)：ynwbosss
利用單片機(jī)具有的智能程序控制的特點(diǎn)，設(shè)計(jì)了基于STC89C52單片機(jī)的"二極管特性測(cè)試器"，可對(duì)二極管一般特性進(jìn)行快速測(cè)試。通過(guò)穩(wěn)定線性電流源給二極管加載恒定電流，然后由高精度模數(shù)轉(zhuǎn)換器測(cè)試其壓降，以此為基礎(chǔ)可判斷二極管好壞、檢測(cè)二極管極性和測(cè)試二極管伏安特性等，避免了用萬(wàn)用表測(cè)試只能測(cè)得極性而不知其特性這一缺點(diǎn)?？捎糜陔娮釉O(shè)計(jì)制作過(guò)程中對(duì)二極管進(jìn)行快速測(cè)試，以確定被測(cè)二極管是否滿足電路的設(shè)計(jì)要求。 Abstract: By making good use of the intelligent control function of the Micro Controller Unit (MCU)， the diode trait tester was designed based on the STC89C52，which could be used to test the trait of a diode rapidly. By loading constant current to diode through the stable linear current source， and measuring the voltage drop of the diode by high-precision analogue-to-digital converter (ADC)， it can judge whether the diode is good or not， distinguish the polarity of the diode， and test the trait that the diode， which can avoid the fault of using a multimeter can only measure the polarity but not the trait. This device can be used to test the trait of a diode quickly，and to make sure that whether a diode can be used in the electronic design or not.
上傳時(shí)間： 2013-11-13
上傳用戶(hù)：assef
Designing read/write device (RWD) units for industrial RF-Identification applications is strongly facilitated by the NXP Semiconductors HITAG Reader Chip HTRC110. All needed function blocks, like the antenna driver, modulator demodulator and antenna diagnosis unit, are integrated in the HTRC110. Therefore only a minimum number of additional passive components are required for a complete RWD. This Application Note describes how to design an industrial RF-Identification system with the HTRC110. The major focus is dimensioning of the antenna, all other external components including clock and power supply, as well as the demodulation principle and its implementatio
標(biāo)簽： HITAG HTRC 110 讀寫(xiě)芯片
上傳時(shí)間： 2013-10-22
上傳用戶(hù)：zhengjian
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