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Notas de Diseño

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  10ВµA Quiescent Current Step-Down Regulators Extend Standby Time in Handheld Products &mdash DN235
  PDF, 83 Kb, Archivo publicado: jul 6, 2001
  Extracto del documento

  advertisement 10ВµA Quiescent Current Step-Down Regulators Extend
  Standby Time in Handheld Products – Design Note 235
  Greg Dittmer
  Importance of Low Quiescent Current
  Many handheld products on the market today are used
  only occasionally but must be kept alive and ready all
  the time. When not being used, the circuitry is powered
  down to save battery energy, with a minimum amount
  of circuitry remaining on. Although the supply current
  is significantly reduced in this low power standby mode,
  the battery energy will still be slowly depleted to power
  the keep-alive circuitry and the regulator. If the device
  spends most of its time in this standby mode, the quiescent current of the regulator can have a significant
  effect on the life of the battery (see Figure 1).
  To maximize the life of the battery in these types of
  products, Linear Technology has extended its family
  of 10ОјA step-down regulators to provide three new
  products. The LTC В®1771 is a constant off-time controller that drives an external P-channel MOSFET for
  output loads up to 5A. The LTC1877 and LTC1878 are
  monolithic regulators that provide constant frequency
  (550kHz) plus synchronous operation for loads up
  to 600mA. Due to their micropower architecture, the
  LTC1771, LTC1877 and LTC1878 require only 10ОјA of …

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  LTC1840: I2C Fan Control Ensures Continuous System Cooling &mdash DN270
  PDF, 82 Kb, Archivo publicado: oct 2, 2001
  Extracto del documento

  I2C Fan Control Ensures Continuous System Cooling
  Design Note 270
  Dilian Reyes
  slowing down due to worn bearings or halted from a
  jam will cause an overflow in the internal counter and
  a corresponding bit is set low in the fault register. The
  system controller can then take action, shutting down
  the faulty fan and summoning maintenance. Introduction
  Linear Technology’s LTC ®1840 is a dual fan speed
  controller for high availability servers and other rackbased network and telecom equipment. The LTC1840
  offers advanced control and monitoring capabilities,
  accessed via an I2C and SMBus compatible 2-wire
  serial interface. In addition to two fan speed control
  channels, the LTC1840 also includes a fan tachometer and fault monitoring, nine slave addresses
  and four general-purpose programmable I/O pins
  in a 16-pin SSOP package. Adjusting fan speed to
  match instantaneous cooling requirements increases
  energy efficiency and reduces noise. By operating at
  reduced speeds, fan bearings are subjected to less
  wear, increasing fan life and reliability. The chip contains four general purpose input/output
  (GPIO) pins that are configured independently. As opendrain outputs, they can be set high, low or to pulse at a
  1.5Hz rate. The outputs are rated at 10mA sink current
  for compatibility with LEDs. Conп¬Ѓgured as inputs, the …

Artículos

• Descargar
  I2C Dual Fan Speed Controller Increases Efficiency and Reduces Noise &mdash LT Journal
  PDF, 46 Kb, Archivo publicado: dic 1, 2001
  Extracto del documento

  DESIGN IDEAS I2C Dual Fan Speed Controller
  Increases Efficiency and
  by Dilian Reyes
  Reduces Noise
  Busy servers and rack-based network and telecom equipment rely on
  hard-working cooling systems to keep
  from melting down. The simplest cooling system is a bank of fans running
  at full tilt, all of the time. This approach ensures a cool environment,
  but overcompensation is neither efficient, nor is it good for the fans. High
  output fans that work full time do not
  last very long (their bearings wear
  out), are not very efficient (they use
  power also), and are noisy (especially
  when their bearings wear out). The
  LTC1840 dual fan speed controller
  reduces the wear on bearings, and
  noise, by continuously adjusting fan
  speed to match the instantaneous
  cooling requirements of the system. REGULATOR
  12V VIN FAN POWER (1.36V TO 12VMAX) VO
  VFB
  1.23V FB R1
  105k …

• Descargar
  10µA Quiescent Current Step-Down Regulator Extends Standby Time in Handheld Electronics &mdash LT Journal
  PDF, 175 Kb, Archivo publicado: feb 1, 2000
  Extracto del documento

  DESIGN FEATURES 10ВµA Quiescent Current Step-Down
  Regulator Extends Standby Time
  by Greg Dittmer
  in Handheld Electronics
  Introduction
  Many handheld products on the market today are used only occasionally
  but must be kept alive and ready all
  the time. When not being used, the
  circuitry is powered down to save
  battery energy, with a minimum
  amount of circuitry remaining on.
  Although the supply current is significantly reduced in this low power
  standby mode, the battery energy will
  still be slowly depleted to power the
  keep-alive circuitry and the regulator. If the device spends most of its
  time in this standby mode, the quiescent current of the regulator can have
  a significant effect on the life of the
  battery (see Figure 1). To maximize
  the life of the battery in these types of
  products, Linear Technology has
  extended its family of low quiescent
  current step-down converters. The
  LTC1474/LTC1475 series broke new …

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Clasificación del fabricante

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