Datasheet Linear Technology LTC1876

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Design Notes

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

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  Efficient DC/DC Converter Provides Two 15A Outputs from a 3.3V Backplane &mdash DN278
  PDF, 86 Kb, File published: Feb 2, 2002
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  advertisement Efficient DC/DC Converter Provides Two 15A Outputs
  from a 3.3V Backplane – Design Note 278
  David Chen
  converter to around 85%. A more efficient solution is to
  use logic-level MOSFETs, which have very low RDS(ON)
  but require a 5V supply. The LTC В®1876 allows the use
  of logic-level MOSFETs by combining a 1.2MHz boost
  regulator, which produces a 5V bias supply from a 3.3V
  input, with two step-down controllers, which provide the
  low voltage outputs. By integrating all three regulators
  in a single IC, the LTC1876 makes for efficient power
  supplies that can be small and inexpensive. Introduction
  The 3.3V DC bus has become popular for broadband
  networking systems, where it is tapped for a variety
  of lower voltages to power DSPs, ASICs and FPGAs.
  These lower voltages range from 1V to 2.5V and often
  require high load currents. To maintain high conversion
  efficiency, power MOSFET conduction losses from the
  step-down converters must be minimized. The problem
  is that the 3.3V bus also brings with it frequent use of
  sub-logic level MOSFETs. Such MOSFETs have a relatively high RDS(ON), limiting the full-load efficiency of a L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered
  trademarks of Linear Technology Corporation. All other trademarks are the property
  of their respective owners. …

Articles

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  Efficient DC/DC Converter Provides Two 15A Outputs from a 3.3V Backplane &mdash LT Journal
  PDF, 68 Kb, File published: May 1, 2002
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  DESIGN IDEAS Efficient DC/DC Converter Provides
  Two 15A Outputs from a 3.3V
  by David Chen
  Backplane
  Introduction
  converter to around 85%. A more
  efficient solution is to use logic-level
  MOSFETs, which have very low RDS(ON)
  but require a 5V supply. The LTC1876
  allows the use of logic-level MOSFETs
  by combining a 1.2MHz boost regulator, which produces a 5V bias supply
  from a 3.3V input, with two stepdown controllers, which provide the
  low voltage outputs. By integrating
  all three regulators in a single IC, the
  LTC1876 makes for efficient power
  supplies that can be small and inexpensive. 96
  94
  OVERALL EFFICIENCY (%) The 3.3V DC bus has become popular
  for broadband networking systems,
  where it is tapped for a variety of
  lower voltages to power DSPs, ASICs
  and FPGAs. These lower voltages
  range from 1V to 2.5V and often require high load currents. To maintain …

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  Triple, High Output Current Supply Requires only 3.3V Input and Minimal Input Capacitance &mdash LT Journal
  PDF, 163 Kb, File published: Nov 1, 2000
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  DESIGN IDEAS Triple, High Output Current Supply
  Requires only 3.3V Input and
  Minimal Input Capacitance
  by San-Hwa Chee
  Introduction
  trollers allow off-the-shelf inductors
  to be used instead of bulky, customwound transformers. The PolyPhaseв„ў
  architecture of the step-down controllers minimizes input capacitance
  requirements, reducing overall system cost and footprint. A built-in boost
  regulator provides a third output. 0.1ВµF
  1
  2
  42.2k
  1% 1000pF 3 20k
  1% 4
  5 0.01ВµF
  6
  220pF 7
  8 6.8k 470pF 9 220pF
  3.3VOUT 10 470pF
  11
  6.8k
  12 …

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Manufacturer's Classification

• Power Management > PMIC & Multifunction > Multitopology DC/DC
• Power Management > Switching Regulator > Step-Down (Buck) Regulators > Multiple Output Buck | External Power Switch Buck Controllers