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Application Notes

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  Power Conditioning for Notebook and Palmtop Systems &mdash AN51
  PDF, 260 Kb, File published: Aug 3, 1992
  Notebook and palmtop systems need a number of voltages developed from a battery. Competitive solutions require small size, high efficiency and light weight. This publication includes circuits for high efficiency 5V and 3.3V switching and linear regulators, back light display drivers and battery chargers. All the circuits are specifically tailored for the requirements outlined above.
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  Application Note 51
  August 1992
  Power Conditioning for Notebook and Palmtop Systems
  Robert Dobkin
  Carl Nelson
  Dennis O’Neill
  Steve Pietkiewicz
  Tim Skovmand
  Milt Wilcox
  INTRODUCTION Battery systems include NiCad, nickel-hydride, lead acid,
  and rechargeable lithium, as well as throw-away alkaline
  batteries. The ability to power condition a wide range
  of batteries makes the ultimate product much more
  attractive because power sources can be interchanged,
  increasing overall system versatility. a very high efficiency (Figure 1) 5V or 3.3V step-down
  (buck) switching regulator. These regulators feature a
  low-loss saturating NPN switch that is normally configured with the negative terminal (emitter) at ground. The
  LT1432 allows the switch to be floated as required in a
  step-down converter, yet still provides full switch saturation for highest efficiency.
  Burst ModeTM is a trademark of Linear Technology Coporation. 100
  NORMAL MODE
  (USE AMPS SCALE)
  90 EFFICIENCY (%) Notebook and palmtop systems need a multiplicity of …

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  Micropower High Side MOSFET Drivers &mdash AN53
  PDF, 226 Kb, File published: Jan 3, 1993
  This application note describes the operation of high-side Nchannel MOSFET switch drivers designed specifically for operation in battery-powered equipment, such as notebook and palmtop computers and portable medical instruments. A selection guide simplifies the proper choice of MOSFET and driver for a particular high-side switch application. Circuits to drive and protect load impedances ranging from large inductors to large capacitors are described and a section on surface mount and copper clad shunts is included.
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  Application Note 53
  January 1993
  Micropower High Side MOSFET Drivers
  Tim Skovmand
  Portable electronic equipment, such as notebook and
  palmtop computers, portable medical instruments and
  battery powered tools, are increasingly dependent upon
  efficient power management to meet the challenge of
  extracting more useful energy (time) from less battery
  volume and weight.
  One link in the power management chain which has
  received increasing scrutiny, as power supply efficiencies
  soar above 90%, is the logic controlled power switch.
  Large sections of a typical notebook computer system, for
  example, are powered via topside or “high side” MOSFET
  switches. These switches can become significant sources
  of power loss if not properly designed.
  At first glance, P-channel MOSFETs appear to be the
  natural choice for high side switching. Unfortunately, the
  RDS(ON) exhibited by most P-channels is prohibitively
  high. (Mother Nature has decreed that electron mobility
  shall exceed hole mobility in silicon by about 2.5 times, so
  that a P-channel MOSFET with the same RDS(ON) and …

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  Power Conversion from Milliamps to Amps at Ultra-High Efficiency (Up to 95%) &mdash AN54
  PDF, 466 Kb, File published: Mar 1, 1993
  This application note discusses the use of the LTC1147, LTC1148, and LTC1149 ultra high efficiency switching regulators in a wide variety of applications. These controllers feature a current-mode architecture which includes an automatic low current operating mode called Burst ModeTM operation, making greater than 90% efficiencies possible at output currents as low as 10mA. This feature maximizes battery life while a product is in sleep or standby modes. In addition, the LTC1148 and LTC1149 are synchronous switching regulators which achieve high efficiency conversion from 10mA to 10A.
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  Application Note 54
  March 1993
  Power Conversion from Milliamps to Amps at Ultra-High
  Efficiency (Up to 95%)
  Dimitry Goder
  Randy Flatness
  INTRODUCTION
  High efficiency is frequently the main goal for power
  supplies in portable computers and hand-held equipment.
  Efficient converters are necessary in these applications to
  minimize power drain on the input source (batteries, etc.)
  and heat buildup in the power components, allowing for
  smaller, lighter, and longer-lived systems. Power conversion efficiency must be in the 90% range in order to meet
  these goals. This application note features power supply
  circuits that satisfy these design requirements and attain
  high efficiency over a wide operating range.
  The recent development of the LTCВ®1142, LTC1143,
  LTC1147, LTC1148, and LTC1149 makes ultra-high efficiency conversion possible. In addition, the LTC1148,
  LTC1149, and LTC1142 are synchronous switching regulators, achieving high efficiency conversion at output
  currents in excess of 10A. These controllers feature a current mode architecture that has automatic Burst
  ModeTM operation at low currents. This technology makes
  90% efficiencies possible at output currents as low as
  10mA, maximizing battery life while a product is in sleep …

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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.
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  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 …

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  PCMCIA Card and Card Socket Power Management: &mdash AN60
  PDF, 260 Kb, File published: Jan 1, 1995
  Most portable systems have expansion sockets conforming to the standards set by the Personal Computer Memory Card International Association (PCMCIA). This standard requires the host to perform an unusual amount of switching on both the VCC and VPP voltage lines. Card designers face difficult power management and DC/DC conversion issues of their own. Board real estate and component height are at a premium making design difficult and component selection critical. This application note discusses in detail both the host and card designer issues and highlights several new products designed specifically for these applications.
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  Application Note 60
  January 1995
  PCMCIA Card and Card Socket Power Management
  Doug La Porte
  INTRODUCTION
  Most portable computers have built-in sockets to accept
  small PC cards for use as extended memories, fax modems, network interfaces, wireless communicators and a
  wide assortment of other functions. The Personal Computer Memory Card International Association (PCMCIA)
  has released specifications that outline the general power
  requirements for these cards.
  The specification calls for an unusual amount of voltage
  switching. Both supplies are switchable to different voltages to accommodate a wide range of card types. The VCC
  supply must provide either 3.3V or 5V. The VPP supply
  must source 12V, 3.3V, 5V, 0V and realize a high impedance state. These diverse, specific requirements call for
  specialized solutions.
  PC card designers may want to design their cards to
  require the VCC supply only. Flash memory card designers who need to ensure a clean VPP supply may generate
  their own 12V on the card. Type I PC cards, at an outside
  thickness of 3.3mm, require ultra-thin highly efficient
  circuitry. The DC/DC converter IC, inductor, capacitors
  and diodes are critical components that require unique
  design to meet the stringent height requirements.
  PCMCIA SOCKET POWER MANAGEMENT …

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  Linear Technology Magazine Circuit Collection, Volume III &mdash AN67
  PDF, 1.2 Mb, File published: Sep 1, 1996
  Application Note 67 is a collection of circuits for data conversion, interface and signal processing from the first five years of Linear Technology. This application note includes circuits such as fast video multiplexers for high speed video, an ultraselective bandpass filter circuit with adjustable gain, and a fully differential, 8-channel, 12-bit A/D system. The categories included in this app note are data conversion, interface, filters, instrumentation, video/op amps and miscellaneous circuits.
  Extract from the document

  Application Note 67
  September 1996
  Linear Technology Magazine Circuit Collection, Volume III
  Data Conversion, Interface and Signal Processing
  Richard Markell, Editor
  INTRODUCTION
  Application Note 67 is a collection of circuits from the first
  five years of Linear Technology, targeting data conversion,
  interface and signal processing applications. This
  Application Note includes circuits such as fast video
  multiplexers for high speed video, an ultraselective
  bandpass filter circuit with adjustable gain and a fully differential, 8-channel, 12-bit A/D system. The categories
  included herein are data conversion, interface, filters,
  instrumentation, video/op amps and miscellaneous
  circuits. Application Note 66, which covers power products
  and circuits from Linear Technology ’s first five years, is
  also available from LTC. ARTICLE INDEX
  Data Conversion . 3
  Fully Differential, 8-Channel, 12-Bit A/D System Using the LTCВ®1390 and LTC1410 . 3
  12-Bit DAC Applications . 5
  LTC1329 Micropower, 8-Bit, Current Output DAC Used for Power Supply Adjustment,
  Trimmer Pot Replacement . 7
  12-Bit Cold Junction Compensated, Temperature Control System with Shutdown . 8 …

Design Notes

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  2-Phase, Dual Switching Regulator Fits in Tight Places &mdash DN210
  PDF, 82 Kb, File published: Aug 1, 1999
  Extract from the document

  advertisement 2-Phase Switching Regulator Fits in Tight Places
  Design Note 210
  Steve Hobrecht The third generation switching regulator controllers
  from Linear Technology address these new requirements. The LTC В®1628, a 2-phase, constant frequency,
  dual synchronous buck controller, has been specifically
  designed to minimize both the size and total cost of the
  power system while delivering the highest efficiency
  in the industry.
  A 2-phase switching technique minimizes the peak
  and resultant RMS input current while doubling the
  effective frequency of the input current pulses. The
  input capacitor ESR requirement is reduced by 40%
  and the capacitance requirement is reduced by 75%
  when compared to a single phase controller solution!
  Ceramic input capacitors provide an ideal choice for
  the resultant requirements. Figure 1 contrasts the
  power loss due to the input RMS ripple current for a
  single and 2-phase solution over the 5V to 25V input
  voltage range for a 5V/3A and 3.3V/3A power supply.
  The input path resistive losses include the ESR of the
  input capacitor, internal battery resistance, PC trace/
  connector losses, fuse resistance and diode or MOSFET
  resistance that may be used in the power path for …

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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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  PC Card Power Management Techniques &mdash DN76
  PDF, 77 Kb, File published: Nov 1, 1993
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  PC Card Power Management Techniques – Design Note 76
  Tim Skovmand
  Most portable computers have sockets built in to accept
  small PC cards for use as extended memories, data/fax
  modems, network interfaces, wireless communicators,
  etc. The Personal Computer Memory Card International
  Association (PCMCIA) has released specifications, 1.0
  and 2.0, which outline the general voltage and power
  requirements for these cards.
  Power is provided by the host computer to the PC card
  through the card socket via the main VCC supply pin(s)
  and the VPP programming supply pins. Both supplies
  can be switched to different voltages to accommodate
  a wide range of card types and applications.
  The VCC supply can be switched from 5V to 3.3V and
  must be capable of supplying upwards of 1A for short
  periods of time and hundreds of milliamps continuously. Three low resistance MOSFET switches are typically used to select the card VCC power as shown in
  Figure 1. The LTC В®1165 inverting triple MOSFET driver
  accepts active-low logic commands directly from a
  common PCMCIA controller and generates gate drive
  voltages above the positive rail to fully enhance low
  5V RDS(ON) N-channel MOSFET switches. Two back-to-back
  MOSFET switches, Q2 and Q3, isolate the parasitic …

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  Triple Output 3.3V, 5V, and 12V High Efficiency Notebook Power Supply &mdash DN78
  PDF, 78 Kb, File published: Jan 1, 1994
  Extract from the document

  advertisement Triple Output 3.3V, 5V, and 12V High Efficiency
  Notebook Power Supply – Design Note 78
  Randy G. Flatness The operating current levels for both regulator sections are user programmable, via external current
  sense resistors, to set current limit. A wide input
  voltage range for the LTC1142 allows operation
  from 4V to 16V. The LTC1142HV extends this voltage range to 20V, permitting operation with up to
  12-cell battery packs.
  Both regulator blocks in the LTC1142 and LTC1142HV
  use a constant off-time current mode architectures
  with Burst Mode operation. This results in a power
  supply that has very high efficiency over a wide load
  current range, fast transient response, and very low
  dropout. The LTC1142 is ideal for applications requiring 5V and 3.3V output voltages with high conversion
  efficiencies over a wide load current range in a small
  amount of board space.
  The application circuit in Figure 2 is configured to
  provide output voltages of 3.3V, 5V, and 12V. The
  current capability of both the 3.3V and 5V outputs
  is 2A (2.5A peak). The logic controlled 12V output
  can provide 150mA (200mA peak), which is ideal for
  flash memory applications. The operating efficiency
  shown in Figure 1 exceeds 90% for both the 3.3V
  and 5V sections. 100 LTC1142 …

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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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  5V to 3.3V Circuit Collection &mdash DN91
  PDF, 74 Kb, File published: Nov 1, 1994
  Extract from the document

  advertisement 5V to 3.3V Circuit Collection – Design Note 91
  Richard Markell and Craig Varga
  High Efficiency 3.3V Regulator
  INPUT
  VOLTAGE
  5V + 6
  VIN
  7
  3 IPGM SHDN 8 3.3V Battery-Powered Supply with Shutdown
  8 3w
  22ОјF*
  25V LBIN 50μH† GND 1N5818 + 2w
  47ОјF**
  16V 4 * AVX TPSD226K025
  ** AVX TPSD476K016
  † COILTRONICS CTX50-4 OUT 1 LT1121-3.3 5V
  5 1
  VOUT
  LTC1174-3.3
  2
  5
  LBOUT
  SW IN 0.1ОјF + 1ОјF …

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  12-Bit Rail-to-Rail Micropower DACs in an SO-8 &mdash DN96
  PDF, 76 Kb, File published: Feb 1, 1995
  Extract from the document

  12-Bit Rail-to-Rail Micropower DACs in an SO-8
  Design Note 96
  Hassan Malik and Jim Brubaker
  The LTC В®1451, LTC1452 and LTC1453 are complete,
  single supply, rail-to-rail voltage output 12-bit digitalto-analog (DAC) converters. They include an output
  buffer amplifier and a space saving SPI compatible
  three-wire serial interface. There is also a data output pin
  that allows daisy-chaining multiple DACs. These DACs
  use a proprietary architecture which guarantees a DNL
  (Differential Nonlinearity) error of less than 0.5LSB. The
  typical DNL error is about 0.2LSB as shown in FigureВ 1.
  There is a built-in power-on reset that resets the output
  to zero scale. The output amplifier can swing to within
  5mV of VCC when unloaded and can source or sink 5mA
  even at a 4.5V supply. These DACs come in an 8-pin
  PDIP and SO-8 package.
  5V and 3V Operation
  The LTC1451 has an on-board reference of 2.048V and
  a nominal output swing of 4.095V. It operates from a
  single 4.5V to 5.5V supply dissipating 2mW (ICC(TYP)
  = 400ОјA).
  The LTC1452 is a multiplying DAC with no on-board
  reference and a full-scale output of twice the reference …

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Manufacturer's Classification

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

Other Names:

LT1121CN8PBF, LT1121CN8 PBF