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Application Notes

• Download
  Linear Technology Magazine Circuit Collection, Volume 1 &mdash AN52
  PDF, 190 Kb, File published: Jan 1, 1993
  This application note consolidates the circuits from the first few years of Linear Technology magazine into one publication. Presented in the note are a variety of circuits ranging from a 50W high efficiency (>90%) switching regulator to steep roll-off filter circuits with low distortion to 12-bit differential temperature measurement systems.
  Extract from the document

  Application Note 52
  January 1993
  Linear Technology Magazine Circuit Collection, Volume 1
  Richard Markell, Editor
  Introduction
  Over the past several years Linear Technology, the magazine, has come of age. From nothing, the publication has
  come into its own, as has its subscriber list. Many innovative circuits have seen the light of day in the pages of our
  now hallowed publication. This Application Note is meant to consolidate the circuits
  from the first few years of the magazine in one place.
  Circuits herein range from laser diode driver circuits to
  data acquisition systems to a 50W high efficiency switcher
  circuit. Enough said. I’ll stand aside and let the authors
  explain their circuits.
  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. CIRCUIT INDEX
  A-to-D Converters .2
  LTC1292: 12-BIT DATA ACQUISITION CIRCUITS .2
  Temperature-Measurement System .2
  Floating, 12-Bit Data Acquisition System .2
  Differential Temperature Measurement System .2
  MICROPOWER SO8 PACKAGED ADC CIRCUITS .4
  Floating 8-Bit Data Acquisition System .4
  0В°C – 70В°C Thermometer .5 …

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  5V to 3.3V Converters for Microprocessor Systems &mdash AN58
  PDF, 310 Kb, File published: 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.
  Extract from the document

  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 …

Design Notes

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  Active Termination for SCSI-2 Bus &mdash DN34
  PDF, 74 Kb, File published: May 1, 1990
  Extract from the document

  Active Termination for SCSI-2 Bus – Design Note 34
  Sean Gold
  Overview of SCSI-2
  The SCSI-2 bus1 is an interface for computers and
  instrumentation that communicate over small distances  — often within the same cabinet. Like GPIB
  (IEEE 488), SCSI’s hardware and software specifications
  are designed to coordinate independent resources such
  as disk and tape drives, п¬Ѓle servers, printers, and other
  computers. SCSI-2 is a bidirectional bus, which must
  be terminated at both ends to 2.85V (Figure 1). The
  terminators are needed because SCSI-2 uses simple
  open collector output drivers in its transceivers. Terminators link communicating devices to the supplies,
  and roughly match the transmission line’s characteristic
  impedance. When the load to the bus increases, the role
  of the termination network becomes more important
  for maintaining signal integrity at high data rates. An
  active termination design is now a part of the SCSI-2
  standard and is presented here in-depth. the bus at regular distances along the cable. Any two
  devices can terminate the cable, but bit error rates are
  minimized with the terminators attached only at the
  ends. Local capacitive loading is low under these conditions, making the transmission line more consistent
  with fewer discontinuities.
  SCSI-2’s key speciп¬Ѓcations are repeated from the ANSI …

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  Techniques for Deriving 3.3V from 5V Supplies &mdash DN74
  PDF, 73 Kb, File published: Sep 1, 1993
  Extract from the document

  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, File published: May 1, 1994
  Extract from the document

  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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Manufacturer's Classification

• Power Management > LDO Linear Regulators > Positive Linear Regulators (LDO)