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LT1018 LT1018

Application Notes

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  Designing Linear Circuits for 5V Single Supply Operation &mdash AN11
  PDF, 230 Kb, File published: Sep 1, 1985
  This note covers the considerations for designing precision linear circuits which must operate from a single 5V supply. Applications include various transducer signal conditioners, instrumentation amplifiers, controllers and isolated data converters.
  Extract from the document

  Application Note 11
  September 1985
  Designing Linear Circuits for 5V Single Supply Operation
  Jim Williams
  In predominantly digital systems it is often necessary
  to include linear circuit functions. Traditionally, separate
  power supplies have been used to run the linear components (see Box, “Linear Power Supplies—Past, Present,
  and Future”).
  Recently, there has been increasing interest in powering
  linear circuits directly from the 5V logic rail. The logic
  rail is a difficult place for analog components to function.
  The high amplitude broadband current and voltage noise
  generated by logic clocking makes analog circuit operation difficult. (See Box, “Using Logic Supplies for Linear
  Functions”.)
  Generally speaking, analog circuitry which must achieve
  very high performance levels should be driven from dedicated supplies. The difficulties encountered in maintaining
  the lowest possible levels of noise and drift in an analog
  system are challenging enough without contending with
  a digitally corrupted power supply.
  Many analog applications, however, can be successfully
  implemented using the logic supply. Combining components intended to provide high performance from the 167Ω Q1 –
  + 2M L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
  Technology Corporation. All other trademarks are the property of their respective owners. RATIOMETRIC …

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  Designs for High Performance Voltage-to-Frequency Converters &mdash AN14
  PDF, 387 Kb, File published: Mar 1, 1986
  A variety of high performance V/F circuits is presented. Included are a 1Hz to 100MHz design, a quartz-stabilized type and a 0.0007% linear unit. Other circuits feature 1.5V operation, sine wave output an nonlinear transfer functions. A separate section examines the trade-offs and advantages of various approaches to V/F conversion.
  Extract from the document

  Application Note 14
  March 1986
  Designs for High Performance Voltage-to-Frequency
  Converters
  Jim Williams
  Monolithic, modular and hybrid technologies have been
  used to implement voltage-to-frequency converters. A
  number of types are commercially available and overall
  performance is adequate to meet many requirements. In
  many cases, however, very high performance or special
  characteristics are required and available units will not work.
  In these instances V→F circuits specifically optimized for
  the desired parameters(s) are required. This application
  note presents examples of circuits which offer substantially improved performance over commercially available
  V→Fs. Various approaches (see Box Section, “V→F
  Design Techniques”) permit improvements in speed, dynamic range, stability and linearity. Other circuits feature
  low voltage operation, sine wave output and deliberate
  nonlinear transfer functions.
  Ultra-High Speed 1Hz to 100MHz V→F Converter
  Figure 1’s circuit uses a variety of circuit methods to
  achieve wider dynamic range and higher speed than any
  commercial V→F. Rocketing along at 100MHz full-scale
  (10% overrange to 110MHz is provided), it leaves all other …

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  Circuitry for Single Cell Operation &mdash AN15
  PDF, 195 Kb, File published: Nov 1, 1985
  1.5V powered circuits for complex linear functions are detailed. Designs include a V/F converter, a 10-bit A/D, sample-hold amplifiers, a switching regulator and other circuits. Also included is a section of component considerations for 1.5V powered linear circuits.
  Extract from the document

  Application Note 15
  November 1985
  Circuitry for Single Cell Operation
  Jim Williams
  Portable, battery-powered operation of electronic apparatus has become increasingly desirable. Medical, remote
  data acquisition, power monitoring and other applications
  are good candidates for battery operation. In some circumstances, due to space, power or reliability considerations,
  it is preferable to operate the circuitry from a single 1.5V
  cell. Unfortunately, a 1.5V supply eliminates almost all
  linear ICs as design candidates. In fact, the LM10 op
  amp-reference and the LTВ®1017/LT1018 comparators are
  the only IC gain blocks fully specified for 1.5V operation.
  Further complications are presented by the 600mV drop
  of silicon transistors and diodes. This limitation consumes
  a substantial portion of available supply range, making
  circuit design difficult. Additionally, any circuit designed
  for 1.5V operation must function at end-of-life battery
  voltage, typically 1.3V. (See Box Section, “Components
  for 1.5V Operation.”)
  500k
  10kHz
  TRIM
  EIN …

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  Micropower Circuits for Signal Conditioning &mdash AN23
  PDF, 2.2 Mb, File published: Apr 1, 1987
  Low power operation of electronic apparatus has become increasingly desirable. AN23 describes a variety of low power circuits for transducer signal conditioning. Also included are designs for data converters and switching regulators. Three appended sections discuss guidelines for micropower design, strobed power operation and effects of test equipment on micropower circuits.
  Extract from the document

  Application Note 23
  April 1987
  Micropower Circuits for Signal Conditioning
  Jim Williams
  Low power operation of electronic apparatus has become
  increasingly desirable. Medical, remote data acquisition,
  power monitoring and other applications are good candidates for battery driven, low power operation. Micropower
  analog circuits for transducer-based signal conditioning
  present a special class of problems. Although micropower
  ICs are available, the interconnection of these devices to
  form a functioning micropower circuit requires care. (See
  Box Sections, “Some Guidelines for Micropower Design
  and an Example” and “Parasitic Effects of Test Equipment
  on Micropower Circuits.”) In particular, trade-offs between
  signal levels and power dissipation become painful when
  performance in the 10-bit to 12-bit area is desirable. Additionally, many transducers and analog signals produce +V inherently small outputs, making micropower requirements complicate an already difficult situation. Despite the
  problems, design of such circuits is possible by combining
  high performance micropower ICs with appropriate circuit
  techniques.
  Platinum RTD Signal Conditioner
  Figure 1 shows a simple circuit for signal conditioning
  a platinum RTD. Correction for the platinum sensor’s
  nonlinear response is included. Accuracy is 0.25В°C over …

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  Thermocouple Measurement &mdash AN28
  PDF, 988 Kb, File published: Feb 1, 1988
  Considerations for thermocouple-based temperature measurement are discussed. A tutorial on temperature sensors summarizes performance of various types, establishing a perspective on thermocouples. Thermocouples are then focused on. Included are sections covering cold-junction compensation, amplifier selection, differential/isolation techniques, protection, and linearization. Complete schematics are given for all circuits. Processor- based linearization is also presented with the necessary software detailed.
  Extract from the document

  Application Note 28
  February 1988
  Thermocouple Measurement
  Jim Williams
  Introduction Thermocouples in Perspective In 1822, Thomas Seebeck, an Estonian physician, accidentally joined semicircular pieces of bismuth and copper
  (Figure 1) while studying thermal effects on galvanic arrangements. A nearby compass indicated a magnetic disturbance. Seebeck experimented repeatedly with different
  metal combinations at various temperatures, noting relative
  magnetic п¬Ѓeld strengths. Curiously, he did not believe that
  electric current was flowing, and preferred to describe the
  effect as “thermo-magnetism.” He published his results in
  a paper, “Magnetische Polarisation der Metalle und Erze
  durch Temperatur-Differenz” (see references). Temperature is easily the most commonly measured
  physical parameter. A number of transducers serve temperature measuring needs and each has advantages and
  considerations. Before discussing thermocouple-based
  measurement it is worthwhile putting these sensors in
  perspective. Figure 2’s chart shows some common contact
  temperature sensors and lists characteristics. Study reveals
  thermocouple strengths and weaknesses compared to
  other sensors. In general, thermocouples are inexpensive,
  wide range sensors. Their small size makes them fast and
  their low output impedance is a benefit. The inherent voltage output eliminates the need for excitation. Subsequent investigation has shown the “Seebeck Effect”
  to be fundamentally electrical in nature, repeatable, and
  quite useful. Thermocouples, by far the most common …

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  Some Thoughts on DC-DC Converters &mdash AN29
  PDF, 1.2 Mb, File published: 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.
  Extract from the document

  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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  Measurement and Control Circuit Collection &mdash AN45
  PDF, 1.2 Mb, File published: Jun 5, 1991
  A variety of measurement and control circuits are included in this application note. Eighteen circuits, including ultra low noise amplifiers, current sources, transducer signal conditioners, oscillators, data converters and power supplies are presented. The circuits emphasize precision specifications with relatively simple configurations.
  Extract from the document

  Application Note 45
  June 1991
  Measurement and Control Circuit Collection
  Diapers and Designs on the Night Shift
  Jim Williams
  Introduction
  During my wife’s pregnancy I wondered what it would
  really be like when the baby was finally born. Before that
  time, there just wasn’t much mothering and fathering to
  do. As a consolation, we busied ourselves watching the
  baby’s heartbeat (Figure 1) on a thrown-together fetal heart
  monitor (see References). feedings. As such, the circuits are annotated with the
  number of feedings required for their completion; e.g., a
  “3-bottle circuit” took three feedings. The circuit’s degree
  of difficulty, and Michael’s degree of cooperation, combined
  to determine the bottle rating, which is duly recorded in
  each figure.
  Low Noise and Drift Chopped Bipolar Amplifier
  Figure 2’s circuit combines the low noise of an LT®1028
  with a chopper based carrier modulation scheme to achieve
  an extraordinarily low noise, low drift DC amplifier. DC
  drift and noise performance exceed any currently available
  monolithic amplifier. Offset is inside 1ОјV, with drift less …

Design Notes

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  Achieving Microamp Quiescent Current in Switching Regulators &mdash DN11
  PDF, 95 Kb, File published: Jun 1, 1988
  Extract from the document

  advertisement Achieving Microamp Quiescent Current in Switching Regulators
  Design Note 11
  Jim Williams
  Many battery powered applications require very wide
  ranges of power supply output current. Normal conditions require currents in the ampere range, while
  standby or “sleep” modes draw only microamperes.
  A typical lap top computer may draw 1 to 2 amperes
  running while needing only a few hundred microamps
  for memory when turned off. In theory, any switching
  regulator designed for loop stability under no-load
  conditions will work. In practice, a regulator’s relatively
  large quiescent current may cause unacceptable battery
  drain during low output current intervals.
  Figure 1 shows a typical flyback regulator. In this
  case the 6V battery is converted to a 12V output by
  the inductive flyback voltage produced each time the
  LT®1070’s VSW pin is internally switched to ground. An
  internal 40kHz clock produces a flyback event every
  25μs. The energy in this event is controlled by the IC’s
  internal error amplifier, which acts to force the feedback
  (FB) pin to a 1.23V reference. The error amplifiers high
  impedance output (the VC pin) uses an RC damper for
  stable loop compensation. …

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  A Battery Powered Lap Top Computer Power Supply &mdash DN18
  PDF, 90 Kb, File published: Dec 1, 1988
  Extract from the document

  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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Manufacturer's Classification

• Signal Conditioning > Comparators > Micropower Comparators