Date Announced: 02 Jun 2005 Linear Technology Corporation announces the LT3477, a current mode, fixed frequency DC/DC converter with dual rail-to-rail current sense amplifiers and an internal 3A, 42V switch. The LT3477 operates from an input voltage range of 2.5V to 25V, making it suitable for a wide variety of applications. It combines a traditional voltage feedback loop and two unique current feedback loops to operate as a constant current and a constant voltage source that is ideal for driving high current LEDs. Both inputs of the error amplifier are available to the user, allowing the LT3477 to be used as either a boost converter, SEPIC or an inverter. It can also be configured as a buck-boost mode or buck-mode LED driver, enabling it to operate in a wide array of applications, even those with fluctuating voltage inputs such as an automotive battery. In addition, its switching frequency can be programmed with a single resistor between 200kHz and 3.5MHz, enabling the designer to minimize external component sizes and avoid “noise critical” frequency bands in the system. A tiny low profile inductor and ceramic capacitors keep solution footprints very compact while minimizing solution cost.The LT3477’s low VCESAT Switch, 0.3V at 2.5A, operates at efficiencies of up to 91%. It features a programmable soft-start function to limit inductor current during start-up and inrush current protection to protect the LT3477 during shorts and line transients. The low profile (0.75mm) 4mm x 4mm QFN-20 package provides excellent thermal performance in a small footprint. The LT3477 is also available in a thermally enhanced 20-pin TSSOP package.The 4mm x 4mm QFN-20 version, the LT3477EUF, and the TSSOP-16E version, the LT3477EFE, are available from stock. Pricing for the LT3477EUF starts at $3.15 each and $3.30 each for the LT3477EFE in 1,000-piece quantities.Summary of Features: LT3477• Dual 100mV (±2.5%) Rail-to-Rail Current Sense Amplifiers• Wide Input Voltage Range: 2.5V to 25V• 3A, 42V Internal Switch• High Efficiency Power Conversion: Up to 91%• Drives LEDs in Buck-Mode, Buck-Boost Mode or Boost Mode• Frequency Set by External Resistor: 200kHz to 3.5MHz• Programmable Soft-Start• Low VCESAT Switch: 0.3V at 2.5A• Capable of Positive and Negative Output Voltages (Boost, Inverting, SEPIC, Flyback)• Available in Thermally Enhanced 20-Lead (4mm x 4mm) QFN and 20-Lead TSSOP Packages
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