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• Descargar
  Lower the Output Voltage Ripple of Positive-to-Negative DC/DC Converters with Optimum Capacitor Hook-Up &mdash LT Journal
  PDF, 146 Kb, Archivo publicado: agosto 9, 2004
  Extracto del documento

  DESIGN IDEAS Lower the Output Voltage Ripple of
  Positive-to-Negative DC/DC
  Converters with Optimum Capacitor
  Hook-Up
  by Keith Szolusha
  Low ripple voltage positive-to-negative DC/DC converters are used in
  many of today’s high frequency and
  noise sensitive disc drives, battery
  powered devices, portable computers, and automotive applications. A
  positive-to-negative converter can
  have very low output ripple voltage
  (similar to a typical buck converter)
  as long as the bulk input capacitor is
  placed between VIN and VOUT, as opposed to placing it between VIN and
  ground. There is a common misconception that positive-to-negative
  converters in the former configuration have noisy outputs, but this
  configuration actually solves noise
  problems rather than introducing
  them. In either configuration (as
  shown in Figures 1a and 1b) the VIN
  and GND pins of an LT1765 are connected to VIN and VOUT respectively.
  Therefore, placing the input capacitor between VIN and VOUT is equivalent
  to placing it between the LT1765’s VIN and GND pins (as shown in Figure …

• Descargar
  Positive Buck Regulator Makes Negative Boost DC/DC Converter &mdash LT Journal
  PDF, 146 Kb, Archivo publicado: marzo 1, 2003
  Extracto del documento

  DESIGN IDEAS Positive Buck Regulator Makes
  Negative Boost DC/DC Converter
  by Keith Szolusha
  Power supply designers can choose
  from a plethora of available positive
  buck regulators that can also be used
  as negative boost DC/DC converters.
  Some buck regulators have a negative
  feedback reference voltage expressly
  for this purpose, but they are far outnumbered by the variety of ICs that
  have positive reference feedback voltages. A designer can take advantage of
  this greater variety of devices by using
  a positive buck switch-mode regulator
  to create an excellent negative boost
  converter—all that is needed are a few
  small modifications to the typical buck
  converter configuration.
  Figure 1a shows a –5V input to –9V
  output at 1.2A negative boost converter
  using the LT1765EFE positive buck converter switch-mode regulator. The
  LT1765EFE operates with a 3V to 25V
  input, uses a 1.2V feedback voltage,
  and has an internal 3A power switch. …

• Descargar
  Space Saving Dual Output ±5V High Current Power Supply Requires Only One 1.25MHz Switcher and One Magnetic Component &mdash LT Journal
  PDF, 54 Kb, Archivo publicado: mayo 1, 2002
  Extracto del documento

  DESIGN IDEAS Space Saving Dual Output В±5V High
  Current Power Supply Requires Only
  One 1.25MHz Switcher and One
  Magnetic Component
  by Keith Szolusha
  ADSL modems, disc drives, notebook computers, and other data
  acquisition circuits require high current, В± 5V power supplies with
  switching frequencies greater than
  1.1MHz to avoid interfering with noise
  sensitive circuitry. Figure 1 shows a
  very simple, compact and efficient
  solution that uses a single 1.25MHz
  LT1765EFE monolithic step-down
  switching regulator and only one
  magnetic component. This circuit can
  provide В±5V supplies from a 12V
  source with greater than 1A capabilities on both rails. The LT1765EFE’s
  internal 3A power switch saves space
  by eliminating the requirement for an
  external MOSFET and its traces. Typical efficiency is 84%, as shown in
  Figure 2. An alternative option is to
  use two ICs, which means paying a
  heavy toll in board space, overall cost, …

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