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06-14-2011

National Semiconductor Introduces Industry's First 2A, Single Inductor, RGB LED Driver for Portable Projectors

National Semiconductor » LM3435

National Semiconductor introduced the industry's first 2A red, green and blue (RGB) LED driver for portable projectors that drives three common anode RGB high-brightness LEDs sequentially with a single inductor. The highly-integrated LM3435 includes an I2C control interface for LED current control.

National Semiconductor - LM3435

National Semiconductor Introduces Industry’s First 2A, Single Inductor, RGB LED Driver for Portable ProjectorsA basic portable or pocket projector LED design today includes a separate driver for each red, green and blue LED and each circuit requires an inductor. The design is bulky and costly, consisting of multiple components to accurately drive the LEDs. The growing popularity of pocket projectors, often smaller than a common two and a half inch portable hard drive, poses increased space constraints. A single LM3435 LED driver from National solves the problem by driving three RGB LEDs sequentially, powering one after another at 60 Hz and above to match the operation requirements of the latest liquid crystal on silicone (LCoS) or digital light processing (DLP) image devices. The much simpler, compact design requires just a single inductor and a few passive components alongside the driver.

National’s LM3435 LED driver joins National’s family of high-brightness projector drivers that include the LM3433 and LM3434 with high frequency dimming and LM3549 0.7A sequential-mode LED driver.

National’s LM3435 RGB LED driver is a highly-integrated, compact switching-mode constant current regulator that drives three LEDs in sequential-mode with a single inductor. The LM3435 integrates all active components, including an N-Channel main MOSFET, P-Channel synchronous MOSFET and three N-Channel pass switches for individual LED control. It accepts input voltage from 2.7V to 5.5V to drive constant current pulses to each red, green and blue high-brightness LED sequentially. The level of current pulses is individually programmed linearly for 1023 steps through an I2C interface. The maximum level of the current pulse can be set by three external current setting resistors to ground from 0.5A to 2.0A respectively. The non-isolated flyback converter with synchronous rectification ensures buck-boost operation at high efficiency.

Features

  • Sequential RGB driving mode
  • Low component count and small solution size
  • Stable with ceramic and other low ESR capacitors, no loop compensation required
  • Fast transient response
  • Programmable converter switching frequency up to 1 MHz
  • MCU interface ready with I2C bus
  • Peak current limit protection for the switcher
  • LED fault detection and reporting via I2C bus

Key Specification

  • Support up to 2A LED current
  • Typical ±3% LED current accuracy
  • Integrated N-Channel main and P-Channel synchronous MOSFETs
  • 3 Integrated N-Channel current regulating pass switches
  • LED Currents programmable via I2C bus independently
  • Input voltage range 2.7V - 5.5V
  • Thermal shutdown
  • Thermally enhanced LLP-40 package

Applications

  • Li-ion batteries / USB Powered RGB LED driver
  • Pico / Pocket RGB LED Projector

national.com

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