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Application Notes

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  2-Wire Virtual Remote Sensing for Voltage Regulators - Clairvoyance Marries Remote Sensing &mdash AN126
  PDF, 1.4 Mb, File published: Oct 1, 2010
  Wires and connectors have resistance. This simple, unavoidable truth dictates that a power source’s remote load voltage will be less than the source’s output voltage. Traditional methods for countering this include increasing the power source voltage and "4-wire" remote voltage sensing. Both have limitations. A new IC based approach achieves "virtual" remote sensing at the load without adding the usual two extra sense wires. Numerous circuit examples show the IC working with various voltage regulators and remote loads. Appendices detail IC internal operation and design guidelines for applying the part in any regulator circuit.
  Extract from the document

  Application Note 126
  October 2010
  2-Wire Virtual Remote Sensing for Voltage Regulators
  Clairvoyance Marries Remote Sensing
  Jim Williams, Jesus Rosales, Kurk Mathews, Tom Hack
  Introduction
  Wires and connectors have resistance. This simple, unavoidable truth dictates that a power source’s remote load
  voltage will be less than the source’s output voltage. Figure 1
  shows this, and implies that intended load voltage can
  be maintained by raising regulator output. Unfortunately,
  line resistance and load variations introduce uncertainties,
  limiting achievable performance.
  WIRING DROPS POWER
  SUPPLY LOAD
  AN125 F01 WIRING DROPS Figure 1. Unavoidable Wiring Drops Cause Low Load
  Voltage. Line and Load Resistance Variations Introduce
  Additional Load Voltage Uncertainty, Mitigating Against
  Compensation by Raising Supply Voltage LOAD
  VOLTAGE
  REGULATOR POWER
  SUPPLY LOAD
  AN125 F02 Figure 2. Local Regulation Stabilizes
  Load Voltage But is Inefп¬Ѓcient VOUT+ VOLTAGE DROP Figure 2 illustrates one compensatory approach. Locally …

Design Notes

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  Tighten Supply Regulation for 2A USB Devices by Dynamically Compensating for Voltage Drops in Wiring and Connectors &mdash DN1029
  PDF, 121 Kb, File published: Feb 27, 2013
  Extract from the document

  Tighten Supply Regulation for 2A USB Devices by Dynamically
  Compensating for Voltage Drops in Wiring and Connectors
  Design Note 1029
  Tom Hack
  Introduction
  These days, the Universal Serial Bus (USB) is commonly
  used to power tablet computers and high rate cell phone
  battery chargers—applications never envisioned at the
  inception of the USB standard in the mid-1990s. The
  USB standard has changed significantly over this time.
  For instance, USB 3.0 requires up to 900mA (six, 150mA
  unit loads) during high bandwidth communication. A
  dedicated charging port can supply as much as 1.8A. of 12V. To simplify the schematic, the protection circuitry
  for load dump, reverse battery, 2-battery jump, spikes
  and noise are not shown (consult Linear Technology’s
  “Automotive Electronics Solutions” brochure for further
  information.) The nominal switching frequency is set
  above 455kHz to avoid interference in the IF of various
  RF devices. It can be raised to 2MHz to avoid interfering
  with AM and Travelers Information Station broadcasts,
  but at the expense of some power supply efficiency. Such high, and highly variable, load currents can
  produce significant and unpredictable voltage drops
  in wiring and connectors, lowering the performance …

Articles

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  Virtual Remote Sensing Improves Load Regulation by Compensating for Wiring Drops Without Remote Sense Lines &mdash LT Journal
  PDF, 1.8 Mb, File published: Jun 30, 2010
  Extract from the document

  July 2010 I N T H I S I S S U E analog multiplier monitors
  instantaneous power and
  simplifies design of
  power control loops 10 regulator with accurate
  input current limit safely
  extracts maximum power
  from USB 22 Virtual Remote Sensing
  Improves Load Regulation by
  Compensating for Wiring Drops
  Without Remote Sense Lines
  Tom Hack and Robert Dobkin clean, efficient, high
  current point-of-load
  power for FPGA and server
  backplanes 28 POWER
  SUPPLY Volume 20 Number 2 CONNECTOR
  DROPS WIRING DROPS Accurately regulating a voltage at a load can be difficult when there
  are significant voltage drops between the power supply and the
  load. Even if a regulator produces a perfectly regulated voltage at its
  own output, variations in load current affect the
  IR drop along the wiring, resulting in significant
  voltage fluctuations at the load (seeВ FigureВ 1). CONNECTOR
  DROPS The conventional solution to improving regulation at the load
  involves adding extra wires for remote sensing (FigureВ 2a), …

Model Line

Manufacturer's Classification

• Monitor, Control and Protection > Cable Drop Compensation
• Space & Harsh Environment > Extended Temperature Plastic (H & MP) > Extended Temperature (H & MP) Power Management