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© rob hill dreamstime.com Components | September 23, 2013

110V LED Controller with Spread Spectrum Frequency Modulation

Linear Technology announces the LT3795, a 110V, high-side current sense DC/DC converter designed to regulate a current or voltage to a constant value, ideal for driving high brightness (HB) LEDs. Its 4.5V to 110V input voltage range.
Summary of Features: LT3795
  • 3000:1 True Color PWM™ Dimming
  • Wide Input Voltage Range: 4.5V to 110V
  • Input & Output Current Reporting
  • PMOS Switch Driver for PWM & Output Disconnect
  • Internal Spread Spectrum Frequency Modulation
  • ±2% Constant Voltage Regulation
  • ±3% Constant Current Regulation:
  • 0V ≤ VOUT ≤ 110V
  • Programmable Input Current limit
  • CTRL Inputs Linearly Adjust LED Current
  • Adjustable Frequency: 100kHz to 1MHz
  • Programmable Open LED Protection with OPENLED Flag
  • Short-Circuit Protection & SHORTLED Flag
  • Programmable Undervoltage Lockout with Hysteresis
  • Soft-Start with Programmable Fault Restart Timer
  • C/10 Detection for Battery Charging
  • Available in 28-Lead TSSOP Package
The LT3795 uses an external low side N-channel MOSFET and can drive up to 90V of white LEDs from a nominal 12V input, delivering in excess of 50 watts. Spread spectrum frequency modulation reduces EMI emissions, while an internal PMOS switch driver delivers robust short-circuit protection in boost and buck-boost topologies.

The LT3795 incorporates a high-side current sense, enabling it to be used in boost, buck, buck-boost or SEPIC topologies. Additionally it offers current both input and output current limiting and monitoring for added reliability and design flexibility. The LT3795 can deliver efficiencies of over 94% in boost mode, minimizing 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 thermally enhanced TSSOP-28 package, the LT3795 offers a very compact HB LED driver or charger solution.

The LT3795 uses PWM dimming, which delivers constant LED color with dimming ranges of up to 3,000:1. For less demanding dimming requirements, the CTRL pin can be used to offer a 10:1 analog dimming range. Its fixed frequency, current mode architecture offers stable operation over a wide range of supply and output voltages.

Robust open and short-circuit protection maximize overall system reliability, while C/10 detection optimizes both battery and SuperCap charging designs. Additional features include input and output current reporting, frequency synchronization, programmable UVLO and a programmable fault restart timer.

The LT3795EFE is available in a thermally enhanced TSSOP-28 package. Pricing starts at $3.45 each. An extended temperature version or I grade, the LT3795IFE, is also available with pricing starting at $3.86 each. Finally, a high temperature, or H grade, the LT3795HFE is available, the pricing starts at $4.11 each. All prices are in 1,000-piece quantities and all versions are available from stock.

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