Linear Technology's LED controller for boost, buck or buck-boost high-current LED apps

Content Dam Leds En Ugc 2009 04 Linear Technology S Led Controller For Boost Buck Or Buck Boost High Current Led Apps Leftcolumn Article Thumbnailimage File
18464 0 thumb Date Announced: 20 Apr 2009

Linear Technology has announced the LT3756, a 100V, high-side current sense DC/DC converter designed to drive high current LEDs. Its 6V to 100V input voltage range makes it ideal for a wide variety of applications, including automotive, industrial and architectural lighting.

The LT3756 uses an external N-channel MOSFET and can drive up to 20 1A white LEDs from a nominal 12V input, delivering in excess of 70 watts. It incorporates a high-side current sense, enabling it to be used in boost, buck, buck-boost or SEPIC and flyback topologies. The LT3756 can deliver efficiencies of over 94% in boost mode, eliminating any 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 3mm x 3mm QFN or a thermally enhanced MSOP-16 package, the LT3756 offers a very compact 70-watt LED driver solution.

The LT3756 uses True Color PWM™ dimming, delivering constant LED color with dimming ranges up to 3,000:1. For less demanding requirements, the CTRL pin can be used to offer a 10:1 analog dimming range. Its 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, making it possible for the converter to operate as a constant-voltage source.

Two versions of the LT3756 are available. The standard LT3756 offers an Open LED Status pin, and the LT3756-1 replaces the Open LED Status pin with a frequency synchronization pin.

Both the LT3756EUD and LT3756EUD-1 are available from stock in a 16-pin 3mm x 3mm QFN package. The LT3756EMSE and LT3756EMSE-1 are both available in a thermally enhanced MSOP-16E package.

Pricing starts at $2.90 each for the QFN package options and $3.00 each for the MSOP-16E options.

Also available from stock are extended temperature versions, or "I" grades, namely the LT3756IUD and LT3755IUD-1, with pricing starting at $3.30 each, in 1,000-piece quantities.

Similarly, "I" grade options of the MSOP-16 versions, the LT3756IMSE and LT3756IMSE-1 are priced starting at $3.40 each in 1,000-piece quantities.

Summary of Features of the LT3756/-1:

· 3000:1 True Color PWM Dimming
· Wide Input Voltage Range: 6V to 100V
· Output Voltage Up to 100V
· Constant-Current & Constant-Voltage Regulation
· 100mV High Side Current Sense
· Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topology
· Adjustable Frequency: 100kHz to 1MHz
· Programmable Undervoltage Lockout with Hysteresis
· Open LED Status Pin (LT3756)
· Frequency Synchronization (LT3756-1)
· PWM Disconnect Switch Driver
· CTRL Pin Provides Analog Dimming
· Low Shutdown Current: <1uA
· Programmable Soft-Start
· Thermally Enhanced 16-Lead QFN 3mm × 3mm Package or MSOP-16E Package

Contact
UK, Ireland, South Africa and Israel: Alastair Boyd, Linear Technology (UK) Limited Tel: +44 (0)1628 477066 E-mail: aboyd@linear.com North America and General Information: Doug Dickinson, Linear Technology Corporation Tel: (408) 432 1900 ext. 2233 E-mail: ddickinson@linear.com

E-mail:uksales@linear.com

Web Site:www.linear.com

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