100kHz，5A，2.5A和1.25A高效开关稳压器
PDF, 692 Kb, 档案已发布: Aug 7, 2007
This ink marks LTC’s eighth circuit collection publication.1 We are continually surprised, to the point of near mystification, by these circuit amalgams seemingly limitless appeal. Reader requests ascend rapidly upon publication, remaining high for years, even decades. All LTC circuit collections, despite diverse content, share this popularity, although just why remains an open question. Why is it? Perhaps the form; compact, complete, succinct and insular. Perhaps the freedom of selection without commitment, akin to window shopping. Or, perhaps, simply the pleasure of new recruits for the circuit aficionados intellectual palate. Locally based electrosociolgists, spinning elegantly contrived theories, offer explanation, but no convincing evidence is at hand. What is certain is that readers are attracted to these compendiums and that calls us to attention. As such, in accordance with our mission to serve customer preferences, this latest collection is presented. Enjoy.
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Application Note 113
August 2007
Power Conversion, Measurement and Pulse Circuits
Tales From the Laboratory Notebook, 2005-2007
Jim Williams
INTRODUCTION
This ink marks LTC’s eighth circuit collection publication.1
We are continually surprised, to the point of near mystification, by these circuit amalgams seemingly limitless
appeal. Reader requests ascend rapidly upon publication,
remaining high for years, even decades. All LTC circuit
collections, despite diverse content, share this popularity, although just why remains an open question. Why is
it? Perhaps the form; compact, complete, succinct and
insular. Perhaps the freedom of selection without commitment, akin to window shopping. Or, perhaps, simply
the pleasure of new recruits for the circuit aficionados
intellectual palate. Locally based electrosociolgists, spinning elegantly contrived theories, offer explanation, but
no convincing evidence is at hand. What is certain is that
readers are attracted to these compendiums and that calls
us to attention. As such, in accordance with our mission
to serve customer preferences, this latest collection is
presented. Enjoy. all with outputs below 600mV, are typical power sources
for such a converter.
Figure 1, an N-channel JFET I-V plot, shows drain-source
conduction under zero bias (gate and source tied together) …
PDF, 2.6 Mb, 档案已发布: Mar 28, 2008
Photomultipliers (PMT), avalanche photodiodes (APD), ultrasonic transducers, capacitance microphones, radiation detectors and similar devices require high voltage, low current bias. Additionally, the high voltage must be pristinely free of noise; well under a millivolt is a common requirement with a few hundred microvolts sometimes necessary. Normally, switching regulator configurations cannot achieve this performance level without employing special techniques. One aid to achieving low noise is that load currents rarely exceed 5mA. This freedom permits output filtering methods that are usually impractical.
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Application Note 118
March 2008
High Voltage, Low Noise, DC/DC Converters
A Kilovolt with 100 Microvolts of Noise
Jim Williams This publication describes a variety of circuits featuring
outputs from 200V to 1000V with output noise below 100ВµV
measured in a 100MHz bandwidth. Special techniques
enable this performance, most notably power stages
optimized to minimize high frequency harmonic content.
Although sophisticated, all examples presented utilize
standard, commercially available magnetics—no custom
components are required. This provision is intended to
assist the user in quickly arriving at a produceable design.
Circuits and their descriptions are presented beginning
with the next ink.
BEFORE PROCEEDING ANY FURTHER, THE READER
IS WARNED THAT CAUTION MUST BE USED IN THE
CONSTRUCTION, TESTING AND USE OF THE TEXT’S
CIRCUITS. HIGH VOLTAGE, LETHAL POTENTIALS ARE
PRESENT IN THESE CIRCUITS. EXTREME CAUTION
MUST BE USED IN WORKING WITH, AND MAKING
CONNECTIONS TO, THESE CIRCUITS. REPEAT: THESE
CIRCUITS CONTAIN DANGEROUS, HIGH VOLTAGE …
PDF, 5.3 Mb, 档案已发布: Aug 23, 1992
Current generation portable computers and instruments utilize backlit liquid crystal displays. The back light requires a highly efficient, high voltage AC source as well as other supply circuitry. AN49 details these circuits and also includes sections on efficiency measurements and instrumentation considerations. A separate section discusses physical and layout considerations for the display.
PDF, 260 Kb, 档案已发布: Aug 3, 1992
Notebook and palmtop systems need a number of voltages developed from a battery. Competitive solutions require small size, high efficiency and light weight. This publication includes circuits for high efficiency 5V and 3.3V switching and linear regulators, back light display drivers and battery chargers. All the circuits are specifically tailored for the requirements outlined above.
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Application Note 51
August 1992
Power Conditioning for Notebook and Palmtop Systems
Robert Dobkin
Carl Nelson
Dennis O’Neill
Steve Pietkiewicz
Tim Skovmand
Milt Wilcox
INTRODUCTION Battery systems include NiCad, nickel-hydride, lead acid,
and rechargeable lithium, as well as throw-away alkaline
batteries. The ability to power condition a wide range
of batteries makes the ultimate product much more
attractive because power sources can be interchanged,
increasing overall system versatility. a very high efficiency (Figure 1) 5V or 3.3V step-down
(buck) switching regulator. These regulators feature a
low-loss saturating NPN switch that is normally configured with the negative terminal (emitter) at ground. The
LT1432 allows the switch to be floated as required in a
step-down converter, yet still provides full switch saturation for highest efficiency.
Burst ModeTM is a trademark of Linear Technology Coporation. 100
NORMAL MODE
(USE AMPS SCALE)
90 EFFICIENCY (%) Notebook and palmtop systems need a multiplicity of …
PDF, 688 Kb, 档案已发布: Aug 1, 1993
This publication details several LCD backlight circuits which feature 92% efficiency. Other benefits include low voltage operation, synchronizing capability, higher output power for color displays, and extended dimming range. Extensive coverage of practical issues includes layout problems, multi-lamp displays, safety and reliability concerns and efficiency and photometric measurements. Also included is a review of circuits which did not work along with appropriate commentary.
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Application Note 55
August 1993
Techniques for 92% Efficient LCD Illumination
Waste Not, Want Not .
Jim Williams
INTRODUCTION
In August of 1992 LTC published Application Note 49,
“Illumination Circuitry for Liquid Crystal Displays.” One
notable aspect of this event is that it generated more
response than all previous LTC application notes combined. This level of interest, along with significant performance advances since AN-49’s appearance, justifies
further discussion of LCD backlighting circuitry.
This publication includes pertinent information from the
previous effort in addition to updated sections and a large
body of new material. The partial repetition is a small
penalty compared to the benefits of text flow, completeness and time efficient communication. The most noteworthy performance advance is achievement of 92%
efficiency for the backlight power supply. Additional new
benefits include low voltage operation, synchronizing capability, higher output power for color displays, and extended dimming range.
A practical 92% efficient LCD backlight design is a classic
study of compromise in a transduced electronic system.
Every aspect of the design is interrelated, and the physical
embodiment is an integral part of the electrical circuit. The
choice and location of the lamp, wires, display housing
and other items has a major effect on electrical characteristics. The greatest care in every detail is required to …
PDF, 1.1 Mb, 档案已发布: Aug 1, 1994
This collection of circuits was worked out between June 1991 and July of 1994. Most were designed at customer request or are derivatives of such efforts. Types of circuits include power converters, transducer signal conditioners, amplifiers and signal generators. Specific circuits include low noise amplifiers, high power single cell DC/DC converters, portable high accuracy barometers, a 10mHz 1% accuracy RMS/DC converter, and random noise generators. Appended sections cover noise theory and present a historical perspective of wideband amplifiers.
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Application Note 61
August 1994
Practical Circuitry for Measurement and Control Problems
Circuits Designed for a Cruel and Unyielding World
Jim Williams
INTRODUCTION currents associated with the continuous operation of fixed
frequency designs. Gated oscillator regulators simply
self-clock at whatever frequency is required to maintain
the output voltage. Typically, loop oscillation frequency
ranges from a few hertz into the kilohertz region, depending upon the load. This collection of circuits was worked out between June
1991 and July of 1994. Most were designed at customer
request or are derivatives of such efforts. All represent
substantial effort and, as such, are disseminated here
for wider study and (hopefully) use.1 The examples are
roughly arranged in categories including power conversion, transducer signal conditioning, amplifiers and signal
generators. As always, reader comment and questions
concerning variants of the circuits shown may be addressed
directly to the author. In most cases this asynchronous, variable frequency operation does not create problems. Some systems, however, are
sensitive to this characteristic. Figure 1 slightly modifies
a gated oscillator type switching regulator by synchronizing its loop oscillation frequency to the systems clock. In
this fashion the oscillation frequency and its attendant
switching noise, albeit variable, become coherent with
system operation. Clock Synchronized Switching Regulator …
PDF, 5.9 Mb, 档案已发布: Nov 1, 1995
This publication, LTC's fourth effort devoted to LCD backlighting in as many years, treats the subject comprehensively. The text considers lamps, display and layout induced losses, circuitry, efficiency related issues, optimization and measurement techniques. Twelve appended sections cover lamp types, mechanical design, electrical and photometric measurement, layout, circuitry and related topics.
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Application Note 65
November 1995
A Fourth Generation of LCD Backlight Technology
Component and Measurement Improvements Refine Performance
Jim Williams PREFACE
Current generation portable computers and instruments
utilize backlit LCDs (liquid crystal displays). These displays
have also appeared in applications ranging from medical
equipment to automobiles, gas pumps and retail terminals.
Cold cathode fluorescent lamps (CCFLs) provide the highest available efficiency for backlighting the display. These
lamps require high voltage AC to operate, mandating an
efficient high voltage DC/AC converter. In addition to good
efficiency, the converter should deliver the lamp drive in
sine wave form. This is desirable to minimize RF emissions.
Such emissions can cause interference with other devices,
as well as degrading overall operating efficiency. The sine
wave excitation also provides optimal current-to-light
conversion in the lamp. The circuit should permit lamp
control from zero to full brightness with no hysteresis or
“pop-on,” and must also regulate lamp intensity vs power
supply variations.
The small size and battery-powered operation associated
with LCD equipped apparatus mandate low component …
PDF, 886 Kb, 档案已发布: Nov 19, 2004
Eighteen circuits are presented in this compilation. Signal sources include a voltage controlled current source, an amplitude/frequency stabilized sine wave oscillator, a versatile, 0V to 50V wideband level shift and four sub-nanosecond pulse generators with risetimes as low as 20ps. Five signal conditioners appear; a unique, single positive rail powered amplifier with output to (and below) zero volts, a milliohmmeter, a 0.02% accurate instrumentation amplifier with 120dB CMRR at 125VCM, a 100MHz switch with 5mV control channel feedthrough and a 5V powered, 15ppm linearity quartz stabilized V→F, converter. The power circuits section features a Xenon flashlamp supply, two 5V powered, 0V to 300V DC/DC converters, a fixed 200V output circuit for APD bias, a 100W 0V to 500V, 28V powered converter and a high current paralleling scheme for linear regulators. Two appended sections consider measurement technique and connection practice in sub-nanosecond circuits.
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Application Note 98
November 2004
Signal Sources, Conditioners and Power Circuitry
Circuits of the Fall, 2004
Jim Williams
Introduction
Occasionally, we are tasked with designing circuitry for a
specific purpose. The request may have customer origins
or it may be an in-house requirement. Alternately, a circuit
may be developed because its possibility is simply too
attractive to ignore1. Over time, these circuits accumulate,
encompassing a wide and useful body of proven capabilities. They also represent substantial effort. These considerations make publication an almost obligatory proposition
and, as such, a group of circuits is presented here. This is
not the first time we have displayed such wares and, given
the encouraging reader response, it will not be the last2.
Eighteen circuits are included in this latest effort, roughly
arranged in the categories given in this publication’s title.
They appear at the next paragraph.
Voltage Controlled Current Source—Ground Referred
Input and Output
A voltage controlled current source with ground referred
input and output is difficult to achieve. Executions exist,
but are often cumbersome, involving numerous components. Figure 1’s conceptual design utilizes a differential …