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Application Notes

• Download
  Voltage Reference Circuit Collection &mdash AN42
  PDF, 1.7 Mb, File published: 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.
• Download
  Efficiency and Power Characteristics of Switching Regulator Circuits &mdash AN46
  PDF, 2.6 Mb, File published: Nov 1, 1991
  Efficiency varies for different DC/DC converters. This application note compares the efficiency characteristics of some of the more popular types. Step-up, step-down, flyback, negative-to-positive, and positive-to-negative are shown. Appended sections discuss how to select the proper aluminum electrolytic capacitor and explain power switch and output diode loss calculations.
• Download
  Data Acquisition Circuit Collection &mdash AN62
  PDF, 349 Kb, File published: Oct 1, 1994
  This application note presents a wide variety of data acquisition circuits. The detailed circuit schematics cover 8-, 10-, and 12- bit ADC and DAC applications, serial and parallel digital interfaces, battery monitoring, temperature sensing, isolated interfaces, and connections to various popular microprocessors and microcontrollers. An appendix covers suggested voltage references.
  Extract from the document

  Application Note 62
  October 1994
  Data Acquisition Circuit Collection
  Kevin R. Hoskins
  INTRODUCTION
  This application note features 8-, 10-, and 12-bit data
  acquisition components in various circuit configurations.
  The circuits include battery monitoring, temperature sensing, isolated serial interfaces, and microprocessor and
  microcontroller serial and parallel interfaces. Also included are voltage reference circuits (Application Note 42
  contains more voltage reference circuits). Additional circuit information is located in the information
  references listed in the Circuit Index. Each information
  reference refers to either an application note (example:
  AN42 = Application Note 42), a data sheet (example:
  LTCВ®1292 DS = LTC1292 Data Sheet), or a design note
  (example: DN66 = Design Note 66).
  and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation. CIRCUIT INDEX
  FIGURE TITLE
  FIGURE NO.
  General Analog-to-Digital Application Circuits
  Two-Quadrant 150kHz Bandwidth Analog Multiplier . Figure 1 .
  Infinite Hold-Time Sample-and-Hold (tACQ = 240ns) . Figure 2 .
  Four-Quadrant 250kHz Bandwidth Analog Multiplier . Figure 3 .
  Demodulating a Signal Using Undersampling . Figure 4 . …

• Download
  A Monolithic Switching Regulator with 100ВµV Output Noise &mdash AN70
  PDF, 1.7 Mb, Language: en, File published: Oct 1, 1997
  This publication details circuitry and applications considerations for the LT1533 low noise switching regulator. Eleven DC/DC converter circuits are presented, some offering <100µV output noise in a 100MHz bandwidth. Tutorial sections detail low noise DC/DC design, measurement, probing and layout techniques, and magnetics selection.
  Extract from the document

  Application Note 70
  October 1997
  A Monolithic Switching Regulator with 100ВµV Output Noise
  “Silence is the perfectest herald of joy .”
  Jim Williams INTRODUCTION
  Size, output flexibility and efficiency advantages have
  made switching regulators common in electronic apparatus. The continued emphasis on these attributes has
  resulted in circuitry with 95% efficiency that requires
  minimal board area. Although these advantages are welcome, they necessitate compromising other parameters. back to the driving source (“reflected” noise) and it is
  radiated. The multiple transmission paths combine with
  the high frequency content to make noise suppression
  difficult. Unconscionable amounts of bypass capacitors,
  ferrite beads, shields, Mu-metal and aspirin have been
  expended in attempts to ameliorate noise-induced effects. Switching Regulator “Noise”
  Something commonly referred to as “noise” is a primary
  concern. The switched mode power delivery that permits
  the aforementioned advantages also creates wideband
  harmonic energy. This undesirable energy appears as
  radiated and conducted components commonly labeled
  as “noise.” Actually, switching regulator output “noise” is
  not really noise at all, but coherent, high frequency residue
  directly related to the regulatorвЂ^TMs switching.1 Figure 1
  shows typical switching regulator output noise. Two distinct characteristics are present. The slow, ramping output …

• Download
  Circuitry for Signal Conditioning and Power Conversion &mdash AN75
  PDF, 508 Kb, File published: Mar 1, 1999
  This publication includes designs for data converters and signal conditioners, transducer circuits, crystal oscillators and power converters. Wideband and micropower circuitry receive special attention. Tutorials on micropower design techniques and parasitic effects of test equipment are included.
  Extract from the document

  Application Note 75
  March 1999
  Circuitry for Signal Conditioning and
  Power Conversion
  Designs From a Once Lazy Sabbatical
  Jim Williams
  Introduction
  Linear Technology has a sabbatical program. Every five
  years employees are granted sabbatical leave, which may
  last up to six weeks. You have 18 months from each five
  year employment anniversary to take the leave. Sabbatical
  is fully company paid and has no restrictions. The time is
  yours to do with as you please.
  People exercise all degrees of freedom with their sabbaticals. They go sailing, they go to South Sea islands, they ski
  some mountain nobody ever heard of, they trek in Nepal.
  Houses get fixed, cars restored and children played with.
  For my third sabbatical I resolved to do absolutely nothing.
  For the first time in my life I was really tired, and I knew it.
  A six week rest sounded just fine. I’d walk the dog and
  spend time with my wife and son. That’s it. No transistors,
  no resistors, no op amps and, above all, no writing. I was
  so written out the thought of picking up a pencil produced
  an instant headache. …

• Download
  Current Sources for Fiber Optic Lasers: A Compendium of Pleasant Current Events &mdash AN90
  PDF, 409 Kb, File published: Apr 1, 2002
  A large group of fiber optic lasers are powered by DC current. Laser drive is supplied by a current source with modulation added to the signal. The current source, although conceptually simple, constitutes an extraordinarily tricky design problem. There are a number of practical requirements for a fiber optic current source and failure to consider them can cause laser and/or optical component destruction. This application note describes ten laser current source circuits with a range of capabilities. High and low current types are presented, along with designs for grounded anode, cathode or floating operation. Each circuit also includes laser protection features. Appended sections cover laser load simulation and current source noise measurement techniques.
  Extract from the document

  Application Note 90
  April 2002
  Current Sources for Fiber Optic Lasers
  A Compendium of Pleasant Current Events
  Jim Williams, Linear Technology Corporation
  INTRODUCTION
  A large group of fiber optic lasers are powered by DC
  current. Laser drive is supplied by a current source with
  modulation added further along the signal path. The
  current source, although conceptually simple, constitutes
  an extraordinarily tricky design problem. There are a
  number of practical requirements for a fiber optic current
  source and failure to consider them can cause laser and/
  or optical component destruction. Protection features must be included to prevent laser and
  optical component damage. The laser, an expensive and
  delicate device, must be protected under all conditions,
  including supply ramp up and down, improper control
  input commands, open or intermittent load connections
  and “hot plugging.”
  Detailed Discussion of Performance Issues Design Criteria for Fiber Optic Laser Current Sources It is useful to expand on the above cursory discussion to
  clarify design goals. As such, each previously called out
  issue is treated in greater detail below. Figure 1 shows a conceptual laser current source. Inputs
  include a current output programming port, an output …

Design Notes

• Download
  Single IC, Power Factor Corrected, Off-Line Supply &mdash DN143
  PDF, 140 Kb, File published: Dec 1, 1996
  Extract from the document

  advertisement Single IC, Power Factor Corrected, Off-Line Supply
  Design Note 143
  Kurk Mathews
  An ever increasing number of off-line power supplies now
  include power factor correction (PFC) in order to reduce
  input current and meet future regulatory requirements.
  Switching power supplies that incorporate a bridge rectifier followed by bulk capacitance create harmonic currents. These harmonics only increase the supply’s RMS
  input current, while contributing nothing to real power.
  The typical solution to this problem has been to add a PFC
  preregulator and a separate controller to an existing
  design.
  The LTВ®1508 (voltage mode) and LT1509 (current mode)
  eliminate the need for separate controllers by combining
  the PFC and a pulse width modulator (PWM) function in a
  single 20-pin IC. PFC is achieved by programming the
  input current of a boost regulator to follow the input line
  voltage. This results in a near-unity power factor compared
  to 0.5 to 0.7 for a typical capacitive input switcher. Linear’s
  unique architecture maintains 0.99 power factor over a
  20:1 load range. Figure 1 shows input current with output
  powers of 30W, 150W and 300W.
  A number of issues associated with a 2-IC approach are
  addressed within the LT1508 and LT1509, resulting in a 2A/DIV 5ms/DIV DN143 F01 Figure 1. Input Current at 30W, 150W and 300W 12/96/143 lower part count and improved PC board layout. Start-up is …

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  Off-Line Low Noise Power Supply Does Not Require Filtering to Meet FCC Emission Requirements &mdash DN175
  PDF, 113 Kb, File published: Mar 1, 1998
  Extract from the document

  advertisement Off-Line Low Noise Power Supply Does Not Require Filtering
  to Meet FCC Emission Requirements – Design Note 175
  Jim Williams
  Introduction
  Off-line power supplies require input п¬Ѓltering components to meet FCC emission requirements. Additionally, board layout is usually quite critical, requiring
  considerable experimentation even for experienced
  off-line supply designers. These considerations derive
  from the wideband harmonic energy generated by the fast switching of traditional off-line supplies. A new
  device, the LTВ®1533 low noise switching regulator,
  eliminates these issues by continuous, closed-loop
  control of voltage and current switching times.1 Additionally, the device’s push-pull output drive eliminates the flyback interval of conventional approaches.
  This further reduces harmonics and smooths input
  1 In depth coverage of this device, its use and performance verification appears
  in LTC Application Note 70, “A Monolithic Switching Regulator with 100μV Output
  Noise,” by Jim Williams. 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. T1 !
  GER
  !
  DAN LTAGE
  O
  V
  H …

• Download
  A Simple Ultra-Low Dropout Regulator &mdash DN32
  PDF, 95 Kb, File published: Mar 1, 1990
  Extract from the document

  advertisement A Simple Ultra-Low Dropout Regulator – Design Note 32
  Jim Williams
  Linear voltage regulators with low dropout characteristics are a frequent requirement, particularly in battery powered applications. It is desirable to maintain
  regulation until the battery is almost entirely depleted.
  Regulator dropout limits significantly impact useful
  battery life, and as such should be minimized. Figure 1
  shows dropout characteristics for a monolithic regulator,
  the LTВ®1085. The …

• Download
  A 4-Cell Ni-Cad Regulator/Charger for Notebook Computers &mdash DN54
  PDF, 77 Kb, File published: Nov 1, 1991
  Extract from the document

  A 4-Cell Ni-Cad Regulator/Charger for
  Notebook Computers -Design Note 54
  Tim Skovmand
  pack can be used to power a 5V notebook computer
  system. Inexpensive N-channel power MOSFETs have
  very low on resistance and can be used to switch power
  with low voltage drop between the battery pack and the
  5V logic circuits. The new LTC В®1155 dual power MOSFET driver delivers
  12V of gate drive to two N-channel power MOSFETs
  when powered from a 5V supply with no external
  components required. This ability, coupled with its
  micropower current demands and protection features,
  makes it an excellent choice for high side switching
  applications which previously required more expensive
  P-channel MOSFETs. Figure 1 shows how a battery charger and an extremely
  low voltage drop 5V regulator can be built using the
  new LTC1155 and three inexpensive power MOSFETs. A notebook computer power supply system is a good
  example of an application which benefits directly from
  this high side driving scheme. A 4-cell, Ni-Cad battery 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. %
  .#3 7
  "
  $633&/5 …

Articles

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  Synchronous, Phase Modulated, Full Bridge Converter Targets Isolated High Power Applications &mdash LT Journal
  PDF, 313 Kb, File published: Sep 1, 2003
  Extract from the document

  DESIGN IDEAS Synchronous, Phase Modulated, Full
  Bridge Converter Targets Isolated High
  by Kurk Mathews
  Power Applications
  Introduction In networking and telecom equipment,
  power supplies provide isolated low
  voltage outputs from the 48V input
  supply rail, with the added requirements of high efficiency (to reduce
  heat dissipation) and low component
  height. These requirements become
  even more difficult to meet with increased power levels, because of the
  corresponding component power dissipation and increased transformer
  size. Simple power supply topologies
  give way to more complex single and
  two-stage approaches that focus on
  transformer and semiconductor utilization.
  One such approach, the phase
  modulated full bridge converter, is a
  popular choice for high power supplies. Unfortunately, until now, there
  has not been a controller that offers
  both the flexibility in timing control
  and features (such as synchronous
  rectifier outputs) to manage a variety …

Model Line

Manufacturer's Classification

• Signal Conditioning > Voltage References > Shunt Voltage References
• Space & Harsh Environment > Military Hermetic (M)
• Space & Harsh Environment > Extended Temperature Plastic (H & MP) > Extended Temperature (H & MP) Voltage References