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LT1372HV LT1377 LT1377

Application Notes

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  A Fourth Generation of LCD Backlight Technology &mdash AN65
  PDF, 5.9 Mb, File published: Nov 1, 1995
  This publication, LTC's fourth effort devoted to LCD backlighting in as many years, treats the subject comprehensively. The text considers lamps, display and layout induced losses, circuitry, efficiency related issues, optimization and measurement techniques. Twelve appended sections cover lamp types, mechanical design, electrical and photometric measurement, layout, circuitry and related topics.
  Extract from the document

  Application Note 65
  November 1995
  A Fourth Generation of LCD Backlight Technology
  Component and Measurement Improvements Refine Performance
  Jim Williams PREFACE
  Current generation portable computers and instruments
  utilize backlit LCDs (liquid crystal displays). These displays
  have also appeared in applications ranging from medical
  equipment to automobiles, gas pumps and retail terminals.
  Cold cathode fluorescent lamps (CCFLs) provide the highest available efficiency for backlighting the display. These
  lamps require high voltage AC to operate, mandating an
  efficient high voltage DC/AC converter. In addition to good
  efficiency, the converter should deliver the lamp drive in
  sine wave form. This is desirable to minimize RF emissions.
  Such emissions can cause interference with other devices,
  as well as degrading overall operating efficiency. The sine
  wave excitation also provides optimal current-to-light
  conversion in the lamp. The circuit should permit lamp
  control from zero to full brightness with no hysteresis or
  “pop-on,” and must also regulate lamp intensity vs power
  supply variations.
  The small size and battery-powered operation associated
  with LCD equipped apparatus mandate low component …

Design Notes

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  Micropower Buck/Boost Circuits, Part 1: Converting Three Cells to 3.3V* &mdash DN109
  PDF, 77 Kb, File published: Aug 1, 1995
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  advertisement Micropower Buck/Boost Circuits, Part 1:
  Converting Three Cells to 3.3V* – Design Note 109
  Mitchell Lee
  Two combinations of cell count and output voltage are
  to be strictly avoided: three cells converted to 3.3V and
  four cells converted to 5V. These combinations are
  troublesome because no ordinary regulator (boost,
  buck or linear) can accommodate a situation where the
  input voltage range overlaps the desired output voltage. the topologies. The LT1372 500kHz converter is used
  for compact layouts at higher current levels.
  You can expect 200mA output from LT1303 based
  circuits and 300mA from the LT1372 circuit without
  modification. All of the circuits feature output disconnect; in shutdown the outputs fall to 0V. The input
  range of LT1303 based converters extends well beyond
  the 3-cell source shown. These function at 1.8V, and
  although not fully characterized for efficiency, can accept inputs of up to 10V. The LT1372 converter operates
  from 2.7V to 10V. This design note presents four circuits capable of solving
  the 3-cell dilemma. Design Note 110 will discuss 4-cell,
  5V circuits. The LT®1303 and LT1372 high efficiency
  DC/DC converters are used throughout, giving a fair
  comparison of each topology’s efficiency. The LT1303
  is optimized for battery operation and includes a lowbattery detector which is required to implement one of 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 …

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  Micropower Buck/Boost Circuits, Part 2: Converting Four Cells to 5V* &mdash DN110
  PDF, 133 Kb, File published: Aug 1, 1988
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  advertisement Micropower Buck/Boost Circuits, Part 2:
  Converting Four Cells to 5V* – Design Note 110
  Mitchell Lee
  Two combinations of cell count and output voltage are to
  be strictly avoided: three cells converted to 3.3V and four
  cells converted to 5V. These combinations are troublesome because no ordinary regulator (boost, buck or linear)
  can accommodate a situation where the input voltage
  range overlaps the desired output voltage. 500kHz converter is used for compact layouts at higher
  current levels.
  You can expect 100mA output from LT1303 based circuits
  and 300mA from the LT1372 circuit without modification.
  All of the circuits feature output disconnect; in shutdown
  the outputs fall to 0V. The input range of LT1303 based
  converters extends well beyond the 3-cell source shown.
  These function at 1.8V, and although not fully characterized
  for efficiency, can accept inputs of up to 10V. The LT1372
  converter operates from 2.7V to 10V. This design note presents four circuits capable of solving
  the 4-cell dilemma. Design Note 109 discussed 3-cell, 3.3V
  circuits. The LT В®1303 and LT1372 high efficiency DC/DC
  converters are used throughout, giving a fair comparison
  of each topology’s efficiency. The LT1303 is optimized for
  battery operation and includes a low-battery detector which
  is required to implement one of the topologies. The LT1372 , LTC and LT are registered trademarks of Linear Technology Corporation. …

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  Monolithic DC/DC Converters Break Speed Limits to Shrink Board Space &mdash DN125
  PDF, 80 Kb, File published: Mar 2, 1996
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  advertisement Monolithic DC/DC Converters Break 1MHz to
  Shrink Board Space – Design Note 125
  Mitchell Lee
  In the never-ending quest for board space, operating
  frequency remains the most important variable in a
  DC/DC converter design. Higher frequency equates
  with smaller coils and capacitors. A new family of fast
  monolithic converters that allows circuit designers to
  reduce the size of their п¬Ѓnished products is now available. Other improvements include quiescent currents
  well below those of slower converters and a new switchdrive technique that reduces dynamic losses by at least
  four fold over previous methods, virtually eliminating
  these losses as a concern in efficiency calculations.
  Table 1 shows the salient features of each member of
  the family. Each is configured as a grounded-switch
  step-up converter, but is equally useful in positive
  and negative high efficiency buck, SEPIC, inverting
  and flyback circuits. The converters are all based
  on the LT В®1372 design, which operates at 500kHz,
  draws 4mA quiescent current and contains a 1.5A,
  0.5О© switch. The LT1371 is designed for higher
  power applications, with a 3A, 0.25О© switch. Supply
  current and operating frequency remain unchanged.
  Reduced quiescent current (1mA) makes the LT1373 …

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  The LT1370: A 500kHz, 6A Monolithic Boost Converter &mdash DN183
  PDF, 78 Kb, File published: Jul 1, 1998
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  advertisement A 500kHz, 6A Monolithic Boost Converter – Design Note 183
  Karl Edwards Circuit Description
  The LT1370 is a current mode switcher. This means that
  switch duty cycle is directly controlled by the switch
  current rather than by the output voltage. This technique has several advantages: immediate response to
  input voltage variations, greatly simplified closed-loop
  frequency compensation, and pulse-by-pulse current
  limiting, which provides maximum switch protection.
  An internal low dropout regulator provides a 2.3V supply
  to all control circuitry. This low dropout design allows
  the input voltage to vary from 2.7V to 30V with virtually
  no change in device performance. An internal 500kHz
  oscillator is the basic clock for all timing. A bandgap
  provides the reference for the feedback error amplifier.
  As with the LT1371, error amplifier circuitry allows the
  LT1370 to directly regulate negative output voltages.
  The NFB pin regulates at –2.48V, while the amplifier’s
  output internally drives the FB pin to 1.245V. The error
  amplifier is a current output (gm) type, so its output
  voltage, present on the VC pin, can be externally clamped
  to lower the current limit. A capacitor-coupled external
  clamp provides soft start.
  The S/S pin has two functions: synchronization and …

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  Capacitor and EMI Considerations New High Frequency Switching Regulators &mdash DN95
  PDF, 82 Kb, File published: Jan 1, 1995
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  advertisement Capacitor and EMI Considerations for New High Frequency
  Switching Regulators – Design Note 95
  Carl Nelson and Bob Essaff Capacitor Technology Considerations
  At lower frequencies, magnetics dominates the size of
  DC-to-DC converters, but at frequencies above 200kHz
  the largest component is typically the input and output
  bypass capacitors. This makes it important to pick the
  right capacitor technology in critical size applications.
  The most important parameter in choosing the capacitor
  is cost versus size and impedance. The input and output
  capacitors must have low impedance at the switching
  frequency to limit voltage ripple and power dissipation.
  It is also desirable to have low impedance at much higher
  frequencies because high amplitude narrow spikes are
  created if the capacitor has even a few nH of inductance.
  The amplitude of these spikes is determined by the
  rate-of-rise of current (dl/dt) fed to the capacitor. For
  a high speed converter, dl/dt may be as high as 0.5A/
  ns. Even 3nH of capacitor lead inductance will create
  (0.5 e9) (3 e–9) = 1.5V spikes. The second part of this
  Design Note shows how to attenuate these spikes using
  parasitic PC board elements.
  Figure 1 details the impedance characteristics of the …

Model Line

Manufacturer's Classification

• Power Management > Switching Regulator > Inverting Regulators
• Power Management > Switching Regulator > Step-Up (Boost) Regulators > Internal Power Switch Boost