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
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.
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.
The LTC®3610 is a high power monolithic synchronousstep-down DC/DC Regulator that can deliver up to 12Aof continuous output current from a 4V to 24V (28Vmaximum) input supply. It is a member of a high currentmonolithic Regulator family (see Table 1) that featuresintegrated low RDS(ON) N-channel top and bottomMOSFETs. This results in a high effi ciency and highpower density solution with few external components.This Regulator family uses a constant on-time valleycurrent mode architecture that is capable of operatingat very low duty cycles at high frequency and with veryfast transient response. All are available in low profi le(0.9mm max) QFN packages.
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.
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.
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
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.
Switching Regulators are of universal interest. LinearTechnology has made a major effort to address this topic.A catalog of circuits has been compiled so that a designengineer can swiftly determine which converter type isbest. This catalog serves as a visual index to be browsedthrough for a specific or general interest.
The LTM4600 DC/DC μModule Regulator is a complete highpower density stepdown Regulator for 10A continuous (14Apeak) loads. The device has two voltage options: 20VINmaximum for the LTM4600EV and 28VIN maximum for theLTM4600HVEV each housed in a small 15mm ¥ 15mm ¥2.8mm LGA surface mount package.
