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Application Notes

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  A Monolithic Switching Regulator with 100ВµV Output Noise &mdash AN70
  PDF, 1.7 Mb, Language: en, File published: Oct 1, 1997
  This publication details circuitry and applications considerations for the LT1533 low noise switching regulator. Eleven DC/DC converter circuits are presented, some offering <100µV output noise in a 100MHz bandwidth. Tutorial sections detail low noise DC/DC design, measurement, probing and layout techniques, and magnetics selection.
  Extract from the document

  Application Note 70
  October 1997
  A Monolithic Switching Regulator with 100ВµV Output Noise
  “Silence is the perfectest herald of joy .”
  Jim Williams INTRODUCTION
  Size, output flexibility and efficiency advantages have
  made switching regulators common in electronic apparatus. The continued emphasis on these attributes has
  resulted in circuitry with 95% efficiency that requires
  minimal board area. Although these advantages are welcome, they necessitate compromising other parameters. back to the driving source (“reflected” noise) and it is
  radiated. The multiple transmission paths combine with
  the high frequency content to make noise suppression
  difficult. Unconscionable amounts of bypass capacitors,
  ferrite beads, shields, Mu-metal and aspirin have been
  expended in attempts to ameliorate noise-induced effects. Switching Regulator “Noise”
  Something commonly referred to as “noise” is a primary
  concern. The switched mode power delivery that permits
  the aforementioned advantages also creates wideband
  harmonic energy. This undesirable energy appears as
  radiated and conducted components commonly labeled
  as “noise.” Actually, switching regulator output “noise” is
  not really noise at all, but coherent, high frequency residue
  directly related to the regulatorвЂ^TMs switching.1 Figure 1
  shows typical switching regulator output noise. Two distinct characteristics are present. The slow, ramping output …

Design Notes

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  New Micropower, Low Dropout Regulators Ease Battery Supply Designs &mdash DN121
  PDF, 85 Kb, File published: Jan 5, 1996
  Extract from the document

  New Micropower, Low Dropout Regulators Ease Battery
  Supply Designs – Design Note 121
  Mitchell Lee and John Seago
  Three new linear regulators simplify the design of
  battery-operated equipment. The LTВ®1521 is a 300mA,
  positive low dropout regulator with micropower quiescent current and shutdown. The LT1175 is a 500mA
  negative complement with adjustable current limit. A
  third product, the LT1118, has the unique capability of
  maintaining output regulation while sourcing or sinking
  load current.
  The LT1521 contains all of the features associated
  with battery-operated applications. In designs where
  memory must be powered continuously, the LT1521’s
  12ОјA quiescent current eliminates the need for a
  separate micropower backup supply. In shutdown the
  quiescent current drops to 6ОјA. Figure 1 shows an
  example application using the LTC В®1477 as a means
  of disconnecting all circuitry except for memory and
  ON/OFF control logic. The LTC1477 protected high
  side switch draws only 10nA in shutdown, eliminating
  itself as well as its load as a factor in battery shelf life.
  In battery-backed memory applications, the output of
  the LT1521 can be held up by the backup battery while …

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Manufacturer's Classification

• Power Management > LDO Linear Regulators > Positive Linear Regulators (LDO)

Other Names:

LT1521CMS8-3TRPBF, LT1521CMS8-3 TRPBF, LT1521CMS83#TRPBF, LT1521CMS8 3#TRPBF