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  Diode Turn-On Time Induced Failures in Switching Regulators &mdash AN122
  PDF, 867 Kb, Archivo publicado: enero 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.
  Extracto del documento

  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 …

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  Some Thoughts on DC-DC Converters &mdash AN29
  PDF, 1.2 Mb, Archivo publicado: 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.
  Extracto del documento

  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 …

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  Switching Regulator Circuit Collection &mdash AN30
  PDF, 606 Kb, Archivo publicado: 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.
  Extracto del documento

  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) …

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  Linear Circuits for Digital Systems &mdash AN31
  PDF, 1.5 Mb, Archivo publicado: 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.
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  High Efficiency Linear Regulators &mdash AN32
  PDF, 818 Kb, Archivo publicado: marzo 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.
  Extracto del documento

  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 …

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  Step Down Switching Regulators &mdash AN35
  PDF, 6.2 Mb, Archivo publicado: agosto 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.
  Extracto del documento

  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 …

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  Voltage Reference Circuit Collection &mdash AN42
  PDF, 1.7 Mb, Archivo publicado: 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.
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  5V to 3.3V Converters for Microprocessor Systems &mdash AN58
  PDF, 310 Kb, Archivo publicado: sept 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.
  Extracto del documento

  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 …

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  Using the LTC1325 Battery Management IC: &mdash AN64
  PDF, 385 Kb, Archivo publicado: agosto 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.
  Extracto del documento

  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 …

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  Linear Technology Magazine Circuit Collection, Volume III &mdash AN67
  PDF, 1.2 Mb, Archivo publicado: sept 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.
  Extracto del documento

  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 …

Notas de Diseño

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  A Battery Powered Lap Top Computer Power Supply &mdash DN18
  PDF, 90 Kb, Archivo publicado: dic 1, 1988
  Extracto del documento

  A Battery Powered Lap Top Computer Power Supply
  Design Note 18
  Brian Huffman
  Most battery powered lap top computers require regulated multiple output potentials. Problems associated
  with such a supply include magnetic and snubber design,
  loop compensation, short circuit protection, size and
  efficiency. Typical output power requirements include
  5V @ 1A for memory and logic circuitry and В±12V
  @ 300mA to drive the analog components. Primary
  power may be either a 6V or 12V battery. The circuit
  in Figure 1 meets all these requirements. The LTВ®1071
  simplifies the power supply design by integrating most
  of the switching regulator building blocks. Also, the
  off-the-shelf transformer eliminates all the headaches
  associated with the magnetic design.
  The circuit is a basic flyback regulator. The transformer
  transfers the energy from the 12V input to the 5V and
  В±12V outputs. Figure 2 shows the voltage (trace A) and
  the current (trace B) waveforms at the VSW pin. The
  VSW output is a collector of a common emitter NPN,
  so current flows through it when it is low. The circuit’s
  40kHz repetition rate is set by the LT1071’s internal
  oscillator. During the VSW (trace A) “on” time, the input …

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  Floating Input Extends Regulator Capabilities &mdash DN21
  PDF, 71 Kb, Archivo publicado: abr 1, 1989
  Extracto del documento

  advertisement Floating Input Extends Regulator Capabilities – Design Note 21
  Brian Huffman
  however, if the secondary windings are isolated from
  one another, a low dropout positive voltage regulator
  can be used for negative regulation (Figure 1). Many applications require circuit performance that is
  unachievable with conventional regulator design. This
  results in added complexity to the circuit. However, some
  problems can easily be solved by floating the input to
  the regulator. A floating input can either be a battery, or
  a secondary winding that is galvanically isolated from
  all other windings. With this method high efficiency
  negative voltage regulation, high voltage regulation, and
  low saturation loss positive buck switching regulator
  can all be achieved easily. In this circuit the LTВ®1086 servos the voltage between
  the output and the adjust pin to 1.25V. The positive
  regulation is accomplished by conventional regulator
  design. Negative voltage regulation is achieved by
  connecting the output of the positive voltage regulator
  to ground. The VIN pin floats to 1.5V or greater, above
  ground. This technique can be used with any positive
  voltage regulator, although highest efficiency occurs
  with low dropout types. Low dropout negative voltage regulators are not currently available. This would seem to preclude high efficiency negative linear regulators. Such regulation is
  frequently desired in switching supply post regulators; L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks …

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  Techniques for Deriving 3.3V from 5V Supplies &mdash DN74
  PDF, 73 Kb, Archivo publicado: sept 1, 1993
  Extracto del documento

  advertisement Techniques for Deriving 3.3V from 5V Supplies – Design Note 74
  Mitchell Lee
  Microprocessor chip sets and logic families that operate from 3.3V supplies are gaining acceptance in both
  desktop and portable computers. Computing rates, and
  in most cases, energy consumed by these circuits show
  a strong improvement over 5V technology. The main
  power supply in most systems is still 5V, necessitating
  a local 5V to 3.3V regulator.
  Linear regulators are viable solutions at lower (IO ≤ 1A)
  currents, but they must have a low dropout voltage in
  order to maintain regulation with a worst-case input
  5 4.5V TO 5.5V IN OUT 1 + LT1129-3.3
  4 SHUTDOWN SENSE 2 GND 3.3V OUT
  700mA
  3.3ОјF
  SOLID TANTALUM of only 4.5V. Figure 1 shows a circuit that converts a
  4.5V minimum input to 3.3V with an output tolerance
  of only 3% (100mV). The LTВ®1129-3.3 can handle up to
  700mA in surface mount configurations, and includes
  both 16ОјA shutdown and 50ОјA standby currents for
  system sleep modes. Unlike other linear regulators, the
  LT1129-3.3 combines both low dropout and low voltage
  operation. Small input and output capacitors facilitate …

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  5V to 3.3V Regulator with Fail-Safe Switchover &mdash DN82
  PDF, 74 Kb, Archivo publicado: mayo 1, 1994
  Extracto del documento

  advertisement 5V to 3.3V Regulator with Fail-Safe Switchover – Design Note 82
  Mitchell Lee
  Newer microprocessors designed for replacing existing
  5V units operate from lower voltage supplies. In the past
  a processor swap was simply a matter of removing one
  IC and replacing it with an updated version. But now
  the upgrade path involves switching from a 5V chip to
  one that requires 3.xxV.
  One means of changing supply voltage from 5V to 3.xxV
  is to clip a jumper that bypasses a local 3.xxV regulator.
  This is not a good solution since it leaves too much to
  chance. Failure to remove the jumper can result in the
  instant destruction of the new microprocessor upon
  application of power. A means of automatically sensing
  the presence of a 3.xxV or 5V processor is necessary.
  Intel microprocessors include a special pin called
  “VOLDET” which can be used to determine whether
  or not a particular chip needs 3.xxV or 5V. Figure 1
  shows a simple circuit that takes advantage of this
  pin to automatically “jumper out” a 3.xxV regulator
  whenever a 5V processor is inserted into the socket. VOLDET is pulled low on 3.xx processors; it is buffered
  by transistor Q2 which grounds the gate of a bypassing
  switch (Q1). Q1 is turned off leaving the LTВ®1085 to …

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