Datasheet Linear Technology LTC1735-1

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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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  A Low Cost Dynamic VID Power Supply for PentiumВ® III Processors &mdash Design Solutions 7
  PDF, 83 Kb, File published: Apr 1, 1999
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  Design Solutions 7
  April 1999
  A Low Cost Dynamic VID Power Supply
  for PentiumВ® III Processors
  INTRODUCTION
  The latest PentiumВ® III mobile processors announced by
  Intel require a 2-level power supply voltage that must be
  dynamically switched. A power supply that satisfies these
  requirements can be constructed using a DC/DC controller
  containing an internal 5-bit DAC. However, substantial
  external circuitry is still required to switch between the two
  operating voltages. This paper presents a new solution
  that satisfies Intel’s dynamic VID requirements, but with
  lower cost, smaller PCB area and better performance than
  competing solutions.
  Many notebook computer manufacturers also prefer the
  VID feature because it provides flexibility to change output
  voltages to support future Intel processors, as well as
  processors from AMD and Cyrix. When using a DC/DC
  converter with a built-in 5-bit DAC, the output voltages
  must be changed by modifying jumpers or zero-ohm
  resistors on the motherboard. The alternative solution
  presented in this paper also provides complete voltage …

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  2-Phase DC/DC Controller Reduces Capacitanceand Increases Battery Life in Portable Applications &mdash Design Solutions 9
  PDF, 106 Kb, File published: Jun 1, 1999
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  Design Solutions 9
  June 1999
  2-Phase DC/DC Controller Reduces Capacitance
  and Increases Battery Life in Portable Applications
  The LTCВ®1628 dual high efficiency DC/DC controller brings
  the considerable benefits of 2-phase operation to portable
  applications for the first time. Notebook computers, PDAs,
  handheld terminals and automotive electronics will all
  benefit from the lower input filtering requirement, reduced
  electromagnetic interference (EMI) and increased efficiency associated with 2-phase operation. coming from the switches, greatly reducing the overlap
  time where they add together (see Figure 1). The result is
  a significant reduction in total RMS input current, which,
  in turn, allows less expensive input capacitors to be used,
  reduces shielding requirements for EMI and improves real
  world operating efficiency.
  Figure 2 compares the input waveforms for a representative 1-phase dual switching regulator to the new LTC1628
  2-phase dual switching regulator. An actual measurement
  of the RMS input current under these conditions shows
  that 2-phase operation lowers the input current from
  2.53ARMS to 1.55ARMS. Why the need for 2-phase operation? Before the LTC1628,
  constant-frequency dual switching regulators operated
  both channels in phase (i.e., 1-phase operation). This
  means that both switches turned on at the same time, …

Articles

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  A Third Generation Dual, Opposing-Phase Switching Regulator Controller &mdash LT Journal
  PDF, 172 Kb, File published: Jun 1, 1999
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  DESIGN FEATURES A Third Generation Dual, OpposingPhase Switching Regulator Controller
  by Steve Hobrecht Introduction
  The LTC1628 is the newest member
  of Linear Technology’s third
  generation of DC/DC controllers. (The
  latest single-output members include
  the LTC1735, LTC1735-1 and the 5bit VID controlled LTC1736.) These
  controllers use a similar constant
  frequency, current mode architecture
  and Burst Mode operation as the
  previous generation LTC1435–
  L TC1439 controllers but with
  improved features. A key new feature
  is control circuitry that drives the two
  top switches 180 degrees out of phase
  to minimize the input capacitance
  requirement and reduce conducted
  and radiated EMI. The resultant input ripple is effectively half the
  amplitude and double the frequency
  of nonphased controllers, significantly
  reducing the input capacitance
  requirement. OPTI-LOOPв„ў compensation, 5V and 3.3V standby
  regulators, new protection circuitry, …

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Manufacturer's Classification

• Power Management > Switching Regulator > Step-Down (Buck) Regulators > External Power Switch Buck Controllers