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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.
  Extract from the document

  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 …

Design Notes

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  Power Supplies for Subscriber Line Interface Circuits &mdash DN130
  PDF, 78 Kb, File published: Jun 2, 1996
  Extract from the document

  Power Supplies for Subscriber Line Interface Circuits
  Design Note 130
  Eddie Beville
  As the demand for world wide networking grows, so
  will the need for advanced data transmission products.
  In particular, ISDN services have become popular because of the recent development of the Internet. ISDN
  provides higher speed data transmission than standard
  modems used in PCs. Also, ISDN supports the standard
  telephone interface (voice and fax), which includes the
  Subscriber Line Interface Circuit. A Subscriber Line
  Interface Circuit requires a negative power supply for
  the interface and the ringer voltages. The power supplies
  described herein are designed for these applications.
  Specifically, these designs address the AMD79R79
  SLIC device with on-chip ringing.
  CIRCUIT DESCRIPTIONS
  LT®1171 Supplies –23.8V at 50mA and
  –71.5V at 60mA
  Figure 1 shows a current mode flyback power supply
  using the LT1171CQ device. This current mode device
  has a wide input voltage range of 3V to 60V, current
  limit protection and an on-chip 65V, 0.30О© bipolar
  D3 …

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  Switching Regulator Allows Alkalines to Replace NiCads &mdash DN41
  PDF, 70 Kb, File published: Nov 1, 1990
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  Switching Regulator Allows Alkalines to Replace NiCads
  Design Note 41
  Brian Huffman
  This circuit is a step-up boost type switching regulator.
  It maintains a constant 6V output as battery voltage
  fails. The inductor accumulates energy from the battery when the LTВ®1270 switch pin (VSW ) switches to
  ground and dumps its stored energy to the output
  when the switch pin (VSW ) goes off. The feedback pin
  (VFB) samples the output from the 6.19k-1.62k divider.
  The LT1270’s error amplifier compares the feedback
  pin voltage to its internal 1.24V reference and controls
  the VSW pin switching current, completing a control
  loop. The output voltage can be varied by changing
  the resistor divider ratio. The RC damper on the VC pin
  provides loop frequency compensation. The minimum
  start up voltage for this circuit is 3V. If a 3.3V start up
  voltage is permissible R1 and Q1 can be removed with
  D2 replaced by a short. In many applications it is desirable to substitute nonrechargeable batteries for chargeable types. This capability is necessary when the NiCads can’t be recharged
  or long charge times are unacceptable. Alkaline batteries are an excellent choice in this situation. They are
  readily available and have reasonable energy density.
  Compared to Alkalines, NiCads provide a more stable
  terminal voltage as they discharge. NiCads decay from
  1.3V to 1.0V, while Alkalines drop from 1.5V to 0.8V. …

Articles

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  Positive-to-Negative Converter Powers В–48V Telecom Circuits &mdash LT Journal
  PDF, 230 Kb, File published: May 1, 1998
  Extract from the document

  DESIGN IDEAS Positive-to-Negative Converter Powers
  by Mitchell Lee
  –48V Telecom Circuits
  If you’re designing a system that
  interfaces to telecom equipment,
  chances are you’ll need a –48V supply. The circuit in Figure 1 supplies
  up to 6W at –48V and scales to more
  than 12W with higher power components. Based on the CГєk topology,
  the converter exhibits excellent efficiency over a wide range of loading
  conditions (see Figure 2).
  The LT1171’s error amplifier is
  designed for positive-boost applications, and hence its gain and reference
  are of the wrong phase and polarity
  for sensing an inverted output. In this
  application, the error amplifier is sim-ply bypassed and feedback is applied
  at the compensation (VC) pin. Zener
  diode D2 senses the output, pulling
  down on Q1 and the VC pin, in
  response to small increases in output
  voltage. Pulling down on the VC pin
  reduces peak switch current, and
  constitutes negative feedback. If the
  output is a little low, the Zener’s …

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Manufacturer's Classification

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