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Application Notes

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  LT1575 UltraFast Linear Controller Makes Fast Transient Response Power Supplies &mdash AN69
  PDF, 224 Kb, File published: Sep 5, 1996
  AN69 describes considerations for linear regulators based on the LT1575 UltraFastTM Linear Regulator controller. The LT1575 drives an external MOSFET pass transistor as an overdriven source follower. This configuration results in an extremely high speed regulation loop which minimizes the need for output capacitors. Target applications are state of the art microprocessor core supplies which exhibit large, high speed load transients while having very tight supply voltage tolerance requirements. The application note shows numerous examples of circuit implementations and offers detailed discussions of design considerations.
  Extract from the document

  Application Note 69
  September 1996
  LT1575 UltraFast Linear Controller Makes
  Fast Transient Response Power Supplies
  Craig Varga
  Introduction
  The current generation of microprocessors places stringent demands on the power supply that powers the
  processor core. Allowable supply voltage variations are as
  low as В±100mV and transient currents are in the range of
  5A with 20ns rise and fall times. These requirements
  demand very accurate, very high speed regulators. The
  linear solutions employed to date rely on monolithic
  regulators or PNP transistors driven by low cost control
  circuits. Because, under the best of circumstances, the
  response times of these circuits to transient loads are
  measured in microseconds, these solutions depend on
  the presence of several hundred microfarads of low ESR
  decoupling capacitance surrounding the CPU. The cost of
  these capacitors is a significant percentage of the total
  power supply cost.
  The LT В®1575 is an UltraFastTM linear controller that drives
  a low cost, N-channel, power MOSFET pass transistor and
  does so with sufficient bandwidth that the bulk decoupling …

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  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 …

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  Linear Technology Magazine Circuit Collection, Volume IV &mdash AN84
  PDF, 2.4 Mb, File published: Apr 1, 2000
  Application Note 84 is a collection of "power circuits" from the years 1996 through 1998 as seen in the pages of Linear Technology magazine. This Application Note collects circuits that can output tens of amps to circuits that can operate a handheld device for several years. In addition to a wide variety of traditional power supply circuits (Buck, Boost, Inverting, Flyback, Linear Regulators, etc.) we include circuits for charging batteries, several Power Management circuits as well as circuits that highlight a very low noise switching regulator.
  Extract from the document

  Application Note 84
  April 2000 Linear Technology Magazine Circuit Collection, Volume IV
  Power Products
  Richard Markell, Editor
  INTRODUCTION
  Application Note 84 is the fourth in a series that excerpts
  useful circuits from Linear Technology magazine to preserve them for posterity. This application note highlights
  “power” circuits from issue VI:1 (February 1996) through
  issue VIII:4 (November 1998). Another application note
  will feature data conversion, interface and signal processing circuits from the same era. Like its predecessor, AN 66,
  this Application Note includes circuits that can power
  most any system you can imagine, from “server” power
  supplies that generate in excess of 50 amps to micropower systems for portable and handheld equipment.
  Also included are power converters that can be voltage programmed using Intel’s VID code. Charge pump converters, linear regulators and battery charger circuits are
  included here, with Li-Ion batteries receiving extra attention. There are, of course, circuits that cannot be so simply
  categorized. Come browse. I’ll get out of the way and let
  the authors describe their creations.
  Note: Article Titles appear in this application note exactly
  as they originally appeared in Linear Technology magazine. This may result in some inconsistency in the usage
  of terminology. TABLE OF CONTENTS
  Introduction . 1
  REGULATORS—SWITCHING (BUCK)
  New LTCВ®1435–LTC1439 DC/DC Controllers Feature Value and Performance . 4 …

Design Notes

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  UltraFast Linear Regulator Eliminates All Bulk Tantalum and Electrolytic Output Capacitors &mdash DN157
  PDF, 92 Kb, File published: Jun 5, 1997
  Extract from the document

  UltraFast Linear Regulator Eliminates All Bulk Tantalum
  and Electrolytic Output Capacitors
  Design Note 157
  Anthony Bonte
  New LTC Regulator Controllers
  The LT1575/LT1577 family of controller ICs drives discrete
  N-channel MOSFETs and produces low dropout,
  UltraFastв„ў transient response regulators. These ICs
  feature 1% typical performance over all DC tolerances.
  Superior transient load performance eliminates all
  bulk output capacitors. An LT1577 based P55C Pentium
  processor power supply operates with only twenty-four
  high frequency decoupling, 1ОјF ceramic capacitors
  required for the microprocessor core. To improve profi t margins, some manufacturers
  reduce output capacitance and ignore the true regulation requirements. Many power supplies are deemed
  reliable if Windows95 boots up more than once.
  Most motherboards are only warranted for 90 days.
  LTC believes that many system crashes (blamed on
  software) are attributable to poor power supply
  regulation. To address these issues, Linear Technology
  introduces the LT В®1575/LT1577. Adjustable and п¬Ѓxed voltage versions accommodate
  any microprocessor voltage. MOSFET RDS(ON) selection allows custom dropout voltage performance. The
  controllers also provide current limiting, on/off control …

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  Very Low Dropout (VLDO) Linear Regulators Supply Low Voltage Outputs &mdash DN292
  PDF, 106 Kb, File published: Aug 2, 2002
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  advertisement Very Low Dropout (VLDO) Linear Regulators Supply
  Low Voltage Outputs
  Design Note 292
  Tom Gross
  Introduction
  With each new generation of computing systems, total
  power continues to increase while system voltages
  fall. CPU core voltages and logic supplies below 1.8V
  are now commonplace. Power supplies must not only
  regulate low output voltages but they must also operate
  from low input voltages. A low voltage, low dropout
  linear regulator is an attractive conversion option for
  applications where output currents are in the several
  ampere range. Component count and cost are low in
  comparison to switching regulator solutions, and with
  low input-to-output voltage differentials, efficiencies
  are comparable. MOSFET controller/driver are devices well suited to
  deliver lower output voltages from a supply of 1.8V
  or lower. Each device offers excellent line/load regulation, temperature performance and transient load
  step response.
  Figure 1 illustrates the LT1580 delivering 1.3V at 3A
  (maximum), from a 1.8V input supply. This particular
  conп¬Ѓguration requires a higher voltage supply to bias …

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Manufacturer's Classification

• Power Management > LDO Linear Regulators > Discrete Pass Element Linear Regulators (LDO)