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80VIN/80VOUT, Constant Voltage, Constant-Current DC/DC Converter

June 03, 2010 | Christoph Hammerschmidt | 222900874
80VIN/80VOUT, Constant Voltage, Constant-Current DC/DC Converter Linear Technology announces the LT3956, an 80V high-side current sense DC/DC converter designed to operate as a constant-current and constant-voltage regulator. The device aims at applications driving high current LEDs as well as charging batteries and supercaps.

Its 4.5V to 80V input voltage range makes it ideal for a wide variety of applications, including automotive, industrial and architectural lighting. The LT3956 uses an internal N-channel MOSFET and can drive up to eighteen 350mA white LEDs from a nominal 12V input, delivering in excess of 25 Watts. It incorporates a high-side current sense, enabling use in boost, buck, buck-boost or SEPIC and flyback topologies. The LT3956 delivers efficiencies of over 94% in boost mode, eliminating the need for external heat sinking. A frequency adjust pin permits the user to program the frequency between 100kHz and 1MHz, optimizing efficiency while minimizing external component size and cost. Combined with a 5mm x 6mm QFN package, the LT3956 offers a highly compact 25 Watt LED driver solution.

The LT3956 uses True Color PWM™ dimming, delivering constant LED color with dimming ranges up to 3,000:1. For less demanding dimming requirements, the CTRL pin provides a 10:1 analog dimming range. The LT3956's fixed frequency, current mode architecture ensures stable operation over a wide range of supply and output voltages. A ground referenced voltage FB pin serves as the input for several LED protection features, enabling the converter to operate as a constant-voltage source.

Summary Features:

- 3000:1 True Color PWM™ Dimming

- Wide Input Voltage Range: 4.5V to 80V

- Output Voltage Up to 80V

- Internal 3.3A/84V Switch

- Constant-Current & Constant-Voltage Regulation

- 250mV High Side Current Sense

- Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topology

- Adjustable Frequency: 100kHz to 1MHz

- Open LED Protection

- Programmable Undervoltage Lockout with Hysteresis

- Constant-Voltage Loop Status Pin

- PWM Disconnect Switch Driver

- CTRL Pin Adjusts High Side Current Sense Threshold

- Low Shutdown Current: <1µA

- Programmable Soft-Start

- Available in the 36-Lead (5mm × 6mm) QFN Package

 The LT3956EUHE is available in a 36-pin 5mm x 6mm QFN package, priced starting at $3.50 each in 1,000-piece quantities. An extended temperature I-grade version, the LT3956IUHE, is priced at $4.12 each, in 1,000-piece quantities. Both versions are available from stock.

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