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.
上傳時間： 2013-11-18
上傳用戶：ZJX5201314
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
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.
上傳時間： 2014-12-24
上傳用戶：569342831
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
Advances in low power electronics now allow placementof battery-powered sensors and other devices in locationsfar from the power grid. Ideally, for true grid independence,the batteries should not need replacement, but instead berecharged using locally available renewable energy, suchas solar power. This Design Note shows how to producea compact battery charger that operates from a small2-cell solar panel. A unique feature of this design is thatthe DC/DC converter uses power point control to extractmaximum power from the solar panel.
上傳時間： 2014-01-20
上傳用戶：wettetw
Linear Technology’s DC/DC step-down μModule®regulators are complete switchmode power supplies in asurface-mount package. They include the DC/DC controller,inductor, power switches and supporting circuitry.These highly integrated regulators also provide an easysolution for applications that require negative outputvoltages. In other words, these products can operate asinverting buck-boost regulators. As a result, the lowestpotential in the circuit is not the standard 0V, but –VOUT,which must be tied to the μModule regulator’s GND. Allsignals are now referred to –VOUT.
上傳時間： 2013-10-22
上傳用戶：ztj182002
Once relegated to the hinterlands of low cost indicatorlights, the LED is again in the spotlight of the lightingworld. LED lighting is now ubiquitous, from car headlightsto USB-powered lava lamps. Car headlights exemplifyapplications that capitalize on the LED’s clear advantages—unwavering high quality light output, tough-assteelrobustness, inherent high effi ciency—while a USBlava lamp exemplifi es applications where only LEDs work.Despite these clear advantages, their requirement forregulated voltage and current make LED driver circuitsmore complex than the venerable light bulb, but some newdevices are closing the gap. For instance, the LTM®8040μModule™ LED driver integrates all the driver circuitryinto a single package, allowing designers to refocus theirtime and effort on the details of lighting design criticalto a product’s success.
上傳時間： 2013-10-16
上傳用戶：togetsomething
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.
上傳時間： 2013-11-05
上傳用戶：coeus
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.
上傳時間： 2013-10-21
上傳用戶：非衣2016
For a variety of reasons, it is desirable to charge batteriesas rapidly as possible. At the same time, overchargingmust be limited to prolong battery life. Such limitation ofovercharging depends on factors such as the choice ofcharge termination technique and the use of multi-rate/multi-stage charging schemes. The majority of batterycharger ICs available today lock the user into one fixedcharging regimen, with at best a limited number ofcustomization options to suit a variety of application needsor battery types. The LTC®1325 addresses these shortcomingsby providing the user with all the functionalblocks needed to implement a simple but highly flexiblebattery charger (see Figure 1) which not only addressesthe issue of charging batteries but also those of batteryconditioning and capacity monitoring.
上傳時間： 2013-10-19
上傳用戶：royzhangsz
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