1.5A低压差正稳压器，可调和固定2.85V，3.3V，3.6V，5V，12V
PDF, 867 Kb, 档案已发布: Jan 16, 2009
Most circuit designers are familiar with diode dynamic characteristics such as charge storage, voltage dependent capacitance and reverse recovery time. Less commonly acknowledged and manufacturer specifi ed is diode forward turn-on time. This parameter describes the time required for a diode to turn on and clamp at its forward voltage drop. Historically, this extremely short time, units of nanoseconds, has been so small that user and vendor alike have essentially ignored it. It is rarely discussed and almost never specified. Recently, switching regulator clock rate and transition time have become faster, making diode turn-on time a critical issue.
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Application Note 122
January 2009
Diode Turn-On Time Induced Failures in Switching
Regulators
Never Has so Much Trouble Been Had By so Many with so Few Terminals
Jim Williams
David Beebe
Introduction A potential difficulty due to diode turn-on time is that
the resultant transitory “overshoot” voltage across the
diode, even when restricted to nanoseconds, can induce
overvoltage stress, causing switching regulator IC failure.
As such, careful testing is required to qualify a given diode
for a particular application to insure reliability. This testing,
which assumes low loss surrounding components and
layout in the п¬Ѓnal application, measures turn-on overshoot
voltage due to diode parasitics only. Improper associated
component selection and layout will contribute additional
overstress terms. Most circuit designers are familiar with diode dynamic
characteristics such as charge storage, voltage dependent
capacitance and reverse recovery time. Less commonly
acknowledged and manufacturer specified is diode forward turn-on time. This parameter describes the time
required for a diode to turn on and clamp at its forward
voltage drop. Historically, this extremely short time, units …
PDF, 1.2 Mb, 档案已发布: Oct 1, 1988
This note examines a wide range of DC/DC converter applications. Single inductor, transformer, and switched-capacitor converter designs are shown. Special topics like low noise, high efficiency, low quiescent current, high voltage, and wide-input voltage range converters are covered. Appended sections explain some fundamental properties of different types of converters.
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Application Note 29
October 1988
Some Thoughts on DC/DC Converters
Jim Williams and Brian Huffman
INTRODUCTION
Many systems require that the primary source of DC power
be converted to other voltages. Battery driven circuitry is
an obvious candidate. The 6V or 12V cell in a laptop computer must be converted to different potentials needed for
memory, disc drives, display and operating logic. In theory,
AC line powered systems should not need DC/DC converters
because the implied power transformer can be equipped
with multiple secondaries. In practice, economics, noise
requirements, supply bus distribution problems and other
constraints often make DC/DC conversion preferable. A
common example is logic dominated, 5V powered systems
utilizing В±15V driven analog components.
The range of applications for DC/DC converters is large,
with many variations. Interest in converters is commensurately quite high. Increased use of single supply powered
systems, stiffening performance requirements and battery
operation have increased converter usage.
Historically, efficiency and size have received heavy emphasis. In fact, these parameters can be significant, but
often are of secondary importance. A possible reason
behind the continued and overwhelming attention to size …
PDF, 606 Kb, 档案已发布: Feb 1, 1989
Switching regulators are of universal interest. Linear Technology has made a major effort to address this topic. A catalog of circuits has been compiled so that a design engineer can swiftly determine which converter type is best. This catalog serves as a visual index to be browsed through for a specific or general interest.
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Application Note 30
February 1989
Switching Regulator Circuit Collection
John Seago
Switching regulators are of universal interest. Linear
Technology has made a major effort to address this topic.
A catalog of circuits has been compiled so that a design
engineer can swiftly determine which converter type is
best. This catalog serves as a visual index to be browsed
through for a specific or general interest. The catalog is organized so that converter topologies can
be easily found. There are 12 basic circuit categories:
Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High
Voltage, Multioutput, Off Line, Preregulator, Switched
Capacitor and Telecom. Additional circuit information can
be located in the references listed in the index. The
reference works as follows, i.e., AN8, Page 2 = Application
Note 8, Page 2; LTC1044 DS = LTC1044 data sheet;
DN17 = Design Note 17. DRAWING INDEX
FIGURE TITLE FIGURE # PAGE REFERENCE/SOURCE Battery
2A Converter with 150ВµA Quiescent Current (6V to 12V)
200mA Output Converter (1.5V to 5V)
Up Converter (6V to 15V)
Regulated Up Converter (5V to 10V) …
PDF, 1.5 Mb, 档案已发布: Feb 2, 1989
Subtitled "Some Affable Analogs for Digital Devotees," discusses a number of analog circuits useful in predominantly digital systems. VPP generators for flash memories receive extensive treatment. Other examples include a current loop transmitter, dropout detectors, power management circuits, and clocks.
PDF, 818 Kb, 档案已发布: Mar 1, 1989
Presents circuit techniques permitting high efficiency to be obtained with linear regulation. Particular attention is given to the problem of maintaining high efficiency with widely varying inputs, outputs and loading. Appendix sections review component characteristics and measurement methods.
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Application Note 32
March 1989
High Efficiency Linear Regulators
Jim Williams
Introduction
Linear voltage regulators continue to enjoy widespread use
despite the increasing popularity of switching approaches.
Linear regulators are easily implemented, and have much
better noise and drift characteristics than switchers. Additionally, they do not radiate RF, function with standard
magnetics, are easily frequency compensated, and have
fast response. Their largest disadvantage is inefficiency.
Excess energy is dissipated as heat. This elegantly simplistic regulation mechanism pays dearly in terms of lost
power. Because of this, linear regulators are associated
with excessive dissipation, inefficiency, high operating
temperatures and large heat sinks. While linears cannot
compete with switchers in these areas they can achieve
significantly better results than generally supposed. New
components and some design techniques permit retention of linear regulator’s advantages while improving
efficiency.
One way towards improved efficiency is to minimize the
input-to-output voltage across the regulator. The smaller
this term is, the lower the power loss. The minimum input/
output voltage required to support regulation is referred …
PDF, 6.2 Mb, 档案已发布: Aug 1, 1989
Discusses the LT1074, an easily applied step-down regulator IC. Basic concepts and circuits are described along with more sophisticated applications. Six appended sections cover LT1074 circuitry detail, inductor and discrete component selection, current measuring techniques, efficiency considerations and other topics.
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Application Note 35
August 1989
Step-Down Switching Regulators
Jim Williams
lost in this voltage-to-current-to-magnetic п¬Ѓeld-to-current-to-charge-to-voltage conversion. In practice, the
circuit elements have losses, but step-down efficiency is
still higher than with inherently dissipative (e.g., voltage
divider) approaches. Figure 2 feedback controls the basic
circuit to regulate output voltage. In this case switch ontime (e.g., inductor charge time) is varied to maintain the
output against changes in input or loading.
REGULATED
OUTPUT IN PULSE
WIDTH
MODULATOR Figure 1 is a conceptual voltage step-down or “buck”
circuit. When the switch closes the input voltage appears
at the inductor. Current flowing through the inductor-capacitor combination builds over time. When the switch
IN OUT AN35 F01 Figure 1. Conceptual Voltage Step-Down (“Buck”) Circuit opens current flow ceases and the magnetic field around
the inductor collapses. Faraday teaches that the voltage
induced by the collapsing magnetic п¬Ѓeld is opposite to the
originally applied voltage. As such, the inductor’s left side
heads negative and is clamped by the diode. The capacitors accumulated charge has no discharge path, and a DC
potential appears at the output. This DC potential is lower
than the input because the inductor limits current during …
PDF, 1.7 Mb, 档案已发布: Jun 1, 1991
A wide variety of voltage reference circuits are detailed in this extensive guidebook of circuits. The detailed schematics cover simple and precision approaches at a variety of power levels. Included are 2 and 3 terminal devices in series and shunt modes for positive and negative polarities. Appended sections cover resistor and capacitor selection and trimming techniques.
PDF, 310 Kb, 档案已发布: Sep 1, 1993
Many popular microprocessors operate from 3.3V supplies, yet they are used in systems where the predominate source of power is 5V. AN58 presents a collection of both linear and switching regulator solutions for conversion of 5V to 3.3V at currents ranging from 100mA to 20A. Applications information and a comparison of various bypass capacitor types is included. Most of the designs can be easily modified for other intermediate voltages such as 3.45V, 3.7V, and 4.1V.
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Application Note 58
September 1993
5V to 3.3V Converters for Microprocessor Systems
Robert Dobkin, Mitchell Lee, Dennis O'Neill and Milt Wilcox
Introduction Linear Regulators The new generation of high performance microprocessors are built on dense, low breakdown voltage processes
in order to accommodate increased transistor counts.
These new processors require high current power at 3.3V,
developed from the 5V input used to power the rest of the
system. Special techniques are required to ensure proper
operation of the microprocessor and good heat dissipation within the computer system. Table 1 shows the range of components available for linear
regulation of 3.3V with a 5V input. With only 1.7V of
headroom, low dropout is essential. Low dropout regulators are available delivering currents from 125mA to 7.5A,
allowing almost any microprocessor to be powered with a
local 3.3V generation circuit. The first four devices (LT1020,
LT1120, LT1121 and LT1129) are PNP micropower low
dropout regulators. Since PNP transistors are much larger
than monolithic NPNs, higher current regulators use an
NPN pass device. The LT1117, LT1086, LT1083 through
LT1085, and LT1087 all use NPN pass devices. The NPN
structure requires about 1.2V headroom compared to the
400mV to 500mV dropout typical of PNP regulators, and
ground current of 5mA or 10mA, independent of output
current. Because of this constant quiescent current, the …
PDF, 385 Kb, 档案已发布: Aug 2, 1996
Application Note 64 details characteristics of various battery types and appropriate charging management schemes. The LTC1325 battery management IC is highlighted along with information for applying it to any type battery. Techniques and circuitry for conditioning, charging and monitoring NiCd, NiMH, Li-Ion and Lead-Acid batteries are presented.
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Application Note 64
August 1996
Using the LTC1325 Battery Management IC
Anthony Ng, Peter Schwartz, Robert Reay,
Richard Markell
INTRODUCTION
For a variety of reasons, it is desirable to charge batteries
as rapidly as possible. At the same time, overcharging
must be limited to prolong battery life. Such limitation of
overcharging depends on factors such as the choice of
charge termination technique and the use of multi-rate/
multi-stage charging schemes. The majority of battery
charger ICs available today lock the user into one fixed
charging regimen, with at best a limited number of
customization options to suit a variety of application needs
or battery types. The LTCВ®1325 addresses these shortcomings by providing the user with all the functional
blocks needed to implement a simple but highly flexible
battery charger (see Figure 1) which not only addresses
the issue of charging batteries but also those of battery
conditioning and capacity monitoring. A microprocessor
interacts with the LTC1325 through a serial interface to
control the operation of its functional blocks, allowing
software to expand the scope and flexibility of the charger …
PDF, 1.2 Mb, 档案已发布: Sep 1, 1996
Application Note 67 is a collection of circuits for data conversion, interface and signal processing from the first five years of Linear Technology. This application note includes circuits such as fast video multiplexers for high speed video, an ultraselective bandpass filter circuit with adjustable gain, and a fully differential, 8-channel, 12-bit A/D system. The categories included in this app note are data conversion, interface, filters, instrumentation, video/op amps and miscellaneous circuits.
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Application Note 67
September 1996
Linear Technology Magazine Circuit Collection, Volume III
Data Conversion, Interface and Signal Processing
Richard Markell, Editor
INTRODUCTION
Application Note 67 is a collection of circuits from the first
five years of Linear Technology, targeting data conversion,
interface and signal processing applications. This
Application Note includes circuits such as fast video
multiplexers for high speed video, an ultraselective
bandpass filter circuit with adjustable gain and a fully differential, 8-channel, 12-bit A/D system. The categories
included herein are data conversion, interface, filters,
instrumentation, video/op amps and miscellaneous
circuits. Application Note 66, which covers power products
and circuits from Linear Technology ’s first five years, is
also available from LTC. ARTICLE INDEX
Data Conversion . 3
Fully Differential, 8-Channel, 12-Bit A/D System Using the LTCВ®1390 and LTC1410 . 3
12-Bit DAC Applications . 5
LTC1329 Micropower, 8-Bit, Current Output DAC Used for Power Supply Adjustment,
Trimmer Pot Replacement . 7
12-Bit Cold Junction Compensated, Temperature Control System with Shutdown . 8 …