Datasheet Linear Technology LT3439 — Datenblatt

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  High Voltage, Low Noise, DC/DC Converters &mdash AN118
  PDF, 2.6 Mb, Datei veröffentlicht: Mar 28, 2008
  Photomultipliers (PMT), avalanche photodiodes (APD), ultrasonic transducers, capacitance microphones, radiation detectors and similar devices require high voltage, low current bias. Additionally, the high voltage must be pristinely free of noise; well under a millivolt is a common requirement with a few hundred microvolts sometimes necessary. Normally, switching regulator configurations cannot achieve this performance level without employing special techniques. One aid to achieving low noise is that load currents rarely exceed 5mA. This freedom permits output filtering methods that are usually impractical.
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  Application Note 118
  March 2008
  High Voltage, Low Noise, DC/DC Converters
  A Kilovolt with 100 Microvolts of Noise
  Jim Williams This publication describes a variety of circuits featuring
  outputs from 200V to 1000V with output noise below 100ВµV
  measured in a 100MHz bandwidth. Special techniques
  enable this performance, most notably power stages
  optimized to minimize high frequency harmonic content.
  Although sophisticated, all examples presented utilize
  standard, commercially available magnetics—no custom
  components are required. This provision is intended to
  assist the user in quickly arriving at a produceable design.
  Circuits and their descriptions are presented beginning
  with the next ink.
  BEFORE PROCEEDING ANY FURTHER, THE READER
  IS WARNED THAT CAUTION MUST BE USED IN THE
  CONSTRUCTION, TESTING AND USE OF THE TEXT’S
  CIRCUITS. HIGH VOLTAGE, LETHAL POTENTIALS ARE
  PRESENT IN THESE CIRCUITS. EXTREME CAUTION
  MUST BE USED IN WORKING WITH, AND MAKING
  CONNECTIONS TO, THESE CIRCUITS. REPEAT: THESE
  CIRCUITS CONTAIN DANGEROUS, HIGH VOLTAGE …

Konstruktionshinweise

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  Ultralow Noise Switching Power Supplies Simplify EMI Compliance &mdash DN316
  PDF, 94 Kb, Datei veröffentlicht: Jul 2, 2003
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  advertisement Ultralow Noise Switching Power Supplies Simplify
  EMI Compliance – Design Note 316
  David Canny
  Introduction
  Most electronic products must pass electromagnetic
  interference (EMI) compliance tests—such as the FCC
  Part 15 rules in the US—before they can be released
  into the market. When a company’s product fails EMI
  compliance tests, the company loses control of the
  development process, shipping dates begin to slip,
  projected revenues diminish and expenses start piling
  up. Furthermore, excessive noise can interfere with
  sensitive electronics within the product itself. So it is
  essential that electronic products are designed from
  the beginning with EMI attenuation in mind. Often the
  EMI compliance problem lies in the product’s switching power supply. In these cases, the best solution is
  prevention by using an ultralow noise switching power
  supply in the initial design, rather than adding shields
  and п¬Ѓlters to the product after the fact. Circuit Description
  Figure 1 shows the LTВ®3439, one of several low noise
  switchers available from Linear Technology. Ultralow
  noise and low EMI are achieved by controlling both
  the output switch voltage and current slew rates. This …

Artikel

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  A Simple Solution to Low Noise, Isolated Power Conversion &mdash LT Journal
  PDF, 181 Kb, Datei veröffentlicht: Nov 1, 2002
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  DESIGN IDEAS A Simple Solution to Low Noise,
  Isolated Power Conversion by Tom Sheehan
  Introduction
  the turns ratio. Rectifiers on the secondary side generate the DC output
  voltage. The output capacitor is for
  hold up and filtering. If required, an
  additional inductor and capacitor can
  be added to reduce the output noise
  even further.
  Control of the voltage and current
  slew rate is maintained via two control loops. One loop controls the
  output switch dV/dt and the other
  loop controls the output switch dI/dt.
  Output slew control is achieved by
  comparing the two currents generated by these slewing events to a
  current set by the external resistor
  RSL.
  The frequency of the internal oscillator can be set from 20kHz to 250kHz
  with an external resistor and capacitor, RT and CT. Each output switch is
  driven at half the frequency of the
  oscillator. The SYNC pin can be used
  to synchronize the switching to an
  external clock. A SHDN pin can be …

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• Power Management > Switching Regulator > Ultralow Noise Regulators | Flyback, Forward and Isolated Controllers