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LTC1709-8

Design Notes

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  Active Voltage Positioning Reduces Output Capacitors &mdash Design Solutions 10
  PDF, 130 Kb, File published: Nov 1, 1999
  Extract from the document

  Design Solutions 10
  November 1999
  Active Voltage Positioning Reduces Output Capacitors
  by Robert Sheehan
  INTRODUCTION
  Power supply performance, especially transient response,
  is key to meeting today’s demands for low voltage, high
  current microprocessor power. In an effort to minimize
  the voltage deviation during a load step, a technique that
  has recently been coined “active voltage positioning” is
  generating substantial interest and gaining popularity in
  the portable computer market. The benefits include lower
  peak-to-peak output voltage deviation for a given load
  step, without having to increase the output filter capacitance. Alternatively, the output filter capacitance can be
  reduced while maintaining the same peak-to-peak transient response.
  BASIC PRINCIPLE
  The term “active voltage positioning” (AVP) refers to
  setting the power supply output voltage at a point that is
  dependent on the load current. At minimum load, the
  output voltage is set to a slightly higher than nominal level.
  At full load, the output voltage is set to a slightly lower than
  nominal level. Effectively, the DC load regulation is
  degraded, but the load transient voltage deviation will be …

Articles

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  LTC1709 Low Cost, High Efficiency 42A Converters with VID Control Reduce Input and Output Capacitors &mdash LT Journal
  PDF, 190 Kb, File published: May 1, 2000
  Extract from the document

  DESIGN IDEAS LTC1709 Low Cost, High Efficiency 42A
  Converters with VID Control Reduce
  Input and Output Capacitors by Wei Chen
  Introduction
  used, resulting in a faster load transient response. This, plus the 5-bit
  VID table, makes these devices particularly attractive for CPU power
  supply applications. Two VID tables
  are available to comply with the
  VRM 8.4 (LTC1709-8) and VRM9.0
  (LTC1709-9) specifications. The LTC1709-8/LTC1709-9 are dual,
  current mode, PolyPhaseв„ў controllers that drive two synchronous buck
  stages out of phase. This architecture
  reduces the number of input and
  output capacitors without increasing
  the switching frequency. The relatively low switching frequency and
  integrated high current MOSFET
  drivers help provide high powerconversion efficiency for low voltage,
  high current applications. Because of
  the output ripple current cancellation, lower value inductors can be
  C1
  1000pF Design Example
  Figure 1 shows the schematic diagram of a 42A power supply for the
  AMD Athlon microprocessor. With …

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Manufacturer's Classification

• Power Management > Switching Regulator > Digitally Programmable Regulators

Other Names:

LTC1709EG-9TRPBF, LTC1709EG-9 TRPBF, LTC1709EG9#TRPBF, LTC1709EG 9#TRPBF