As the perfOrmance of many handheld devices approachesthat of laptop computers, design complexity also increases.Chief among them is thermal management—how doyou meet increasing perfOrmance demands while keepinga compact and small product cool in the user’s hand?FOr instance, as battery capacities inevitably increase,charge currents will also increase to maintain Or improvetheir charge times. Traditional linear regulatOr-based batterychargers will not be able to meet the charge currentand effi ciency demands necessary to allow a product tOrun cool. What is needed is a switching-based chargerthat takes just about the same amount of space as a linearsolution—but without the heat.
上传时间： 2013-11-23
上传用户：lu2767
Video cable driver amplifi er output stages traditionallyrequire a supply voltage of at least 6V in Order to providethe required output swing. This requirement is usuallymet with 5V supplies by adding a boost regulatOr Or asmall local negative rail, say via the popular LT®1983-3.Such additional circuitry is unnecessary in typical 1VP-Pvideo connections, such as HD component video, if thecable driver amplifi ers simply offer near rail-to-rail outputcapability when powered from 5V.
上传时间： 2013-11-16
上传用户：yanyangtian
The LTC®3562 quad output step-down regulatOr is designedfOr multicOre handheld microprocessOr applications thatoperate from a single Li-Ion battery. Its four monolithic, higheffi ciency buck regulatOrs suppOrt Intel’s mobile CPU P-Stateand C-State energy saving operating modes. The outputvoltages are independently controllable via I2C, and eachoutput can be independently started and shut down. Designerscan choose from power saving pulse-skipping mode OrBurst Mode® operation, Or select low noise LDO mode. Thespace-saving LTC3562 is available in a 3mm × 3mm QFNpackage and requires few external components.
上传时间： 2013-10-07
上传用户：1583060504
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
上传时间： 2013-11-18
上传用户：hulee
The LTC®3569 is a compact power solution fOr handhelddevices. Its tiny 3mm × 3mm QFN package includesthree buck regulatOrs with individually programmableoutput voltages. One regulatOr suppOrts load currentsup to 1200mA, while the other two suppOrt currents to600mA. Two regulatOrs can be paralleled fOr increasedload capability. Each current-mode regulatOr is internallycompensated with excellent load and line regulation. Acomplete 2- Or 3-output solution requires a minimumof external passive components.
上传时间： 2013-10-11
上传用户：yxgi5
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
上传时间： 2013-11-04
上传用户：wfl_yy
The LTC3546 is a dual output current mode buck regulatOrwith fl exible output current partitioning. Beyondthe advantages nOrmally associated with dual outputregulatOrs (reduced size, cost, EMI and part count, withimproved effi ciency), the LTC3546’s outputs can bepartitioned fOr either 3A and 1A outputs, Or two 2A outputs.This increases its application range and simplifi esmultiple supply rail designs. A confi gurable Burst Mode®clamp fOr each output sets the current transition levelbetween Burst Mode operation and fOrced continuousconduction mode to optimize effi ciency over the entireoutput range. An adjustable switching frequency up to4MHz and internal power MOSFET switches allow fOrsmall and compact footprints.
上传时间： 2013-11-04
上传用户：yxgi5
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.
上传时间： 2013-11-05
上传用户：coeus
What would happen if someone connected 24V to your12V circuits? If the power and ground lines were inadvertentlyreversed, would the circuits survive? Does yourapplication reside in a harsh environment, where the inputsupply can ring very high Or even below ground? Evenif these events are unlikely, it only takes one to destroya circuit board.
上传时间： 2013-10-26
上传用户：jackandlee
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.
标签： 电压基准
上传时间： 2013-10-15
上传用户：liuwei6419
