Datasheet Linear Technology LT3477

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Design Notes

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  Monolithic Converter Drives High Power LEDs &mdash DN376
  PDF, 77 Kb, File published: Sep 19, 2005
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  Monolithic Converter Drives High Power LEDs – Design Note 376
  Keith Szolusha
  Introduction
  High power LEDs are quickly expanding their reach as
  the light source of choice for flat panel computer and
  TV monitors, TV projection, signage, portable lights
  and automotive interior, trim and brake lighting. The
  input voltage and LED voltage combinations across
  these applications are as diverse as the applications
  themselves, precluding the ability for a single topology
  to satisfy the needs of them all. Nevertheless, all LED
  drivers, whether buck, boost, buck-boost or SEPIC must
  regulate a constant LED current, regardless of input and
  output voltages. Now a single switching regulator with
  the ability to be configured in a large variety of topologies for high power constant LED current is available. Efficiencies of up to 91% can be achieved in typical
  applications. The LT3477 features a programmable
  soft-start function to limit inductor current during
  start-up. Both inputs of the error amplifier are available externally, allowing positive and negative output
  voltages. The switching frequency is programmable
  from 200kHz to 3.5MHz through an external resistor.
  It comes in two thermally enhanced packages: a 20-pin
  (4mm Г— 4mm) QFN and a 20-pin TSSOP.
  Boost Driver …

Articles

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  Constant Current from 3A DC/DC Converter with 2 Rail-to-Rail Current Sense Amplifiers &mdash LT Journal
  PDF, 201 Kb, File published: Mar 28, 2006
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  DESIGN FEATURES Constant Current from 3A DC/DC
  Converter with 2 Rail-to-Rail
  by Daniel Chen
  Current Sense Amplifiers
  Introduction
  Traditional DC/DC converters use
  voltage feedback for constant output
  voltage regulation. There are many
  applications, however, that need to
  regulate a constant output current.
  Driving LEDs in series is one such
  application. The LT3477 combines a
  traditional voltage feedback loop and
  two unique current feedback loops
  to operate as a constant-current,
  constant-voltage source. It is a current mode, 3A DC/DC converter with
  dual rail-to-rail 100mV current sense
  amplifiers that can be configured as a
  buck mode or buck-boost mode LED
  driver. It is versatile enough to also be
  configured as an input-output current limited boost, SEPIC or inverting
  converter. Both current sense voltages
  can be adjusted independently using …

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  3A Converter Drives LEDs with 500:1 Dimming &mdash LT Journal
  PDF, 289 Kb, File published: Mar 28, 2006
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  DESIGN IDEAS L 3A Converter Drives LEDs
  with 500:1 Dimming by Jaino Parasseril Introduction DESIGN IDEAS
  3A Converter Drives LEDs
  with 500:1 Dimming .37
  Jaino Parasseril 40nVP–P Noise, 0.05µV/°C Drift,
  Chopped FET Amplifier .39
  Jim Williams 100 VIN = 5V
  4 LEDs
  fPWM = 100Hz 10 1 0.1 0.1 10
  1
  PWM DUTY CYCLE (%) Save Board Space with a High
  Efficiency Dual Synchronous,
  400mA/800mA, 2.25MHz
  Step-Down DC/DC Regulator .44
  Damon Lee Linear Technology Magazine March 2006 Figure 3), resulting in a wide dimming
  range of 500:1 at a PWM frequency
  of 100Hz.
  The LED current can be controlled
  by feeding a PWM signal with a broad
  range of frequencies. Dimming below
  80Hz is possible but not desirable due
  to perceptible flashing of LEDs at lower
  frequencies. The LED current can be …

Model Line

Manufacturer's Classification

• Power Management > Switching Regulator > SEPIC Regulators
• Power Management > Switching Regulator > Step-Up (Boost) Regulators > Internal Power Switch Boost
• Power Management > LED Driver ICs > Step-Up (Boost) LED Drivers | Step-Down (Buck) LED Drivers | Buck-Boost LED Drivers | Multitopology LED Driver