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DC/DC Converter: LT3518

August 22, 2012
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LT3518Linear Technology announces the H-grade version of the LT3518. The LT3518 is a 45 V, high-side current sense DC/DC converter designed to drive high current LEDs at constant current. Its 3 to 30 V input voltage range with transient protection to 40 V makes the LT3518 ideal for a wide variety of applications, including automotive, industrial and architectural lighting.

The H-grade version operates with a junction temperature up to 150°C, compared to the E- and I-grade versions’ 125°C maximum junction temperature. All electrical specifications are identical for the E, I and H. The H-grade parts are tested and guaranteed to the maximum junction temperature of 150°C. They are ideal for automotive and industrial applications, which are subjected to high ambient temperatures.

The LT3518 can drive up to eight 300mA white LEDs from a nominal 12V input, making it well suited for applications such as automotive display backlighting. The LT3518 senses output current at the high side of the LED, enabling buck, buck-boost or boost configurations. It can deliver efficiencies up to 90% in boost mode from a 4mm x 4mm QFN package. The LT3518 offers True Color PWM™ dimming, delivering constant LED color with dimming ranges of up to 3,000:1. For less demanding dimming requirements, the CNTRL pin can be used to offer 10:1 analog dimming. Its fixed frequency, current-mode architecture ensures stable operation over a wide range of supply and output voltages. A frequency adjust pin enables the user to program the frequency between 250kHz and 2.5MHz to optimize efficiency while minimizing external component size.

The LT3518HUF is available from stock in 16-pin QFN package, priced starting at $3.79 each in 1,000-piece quantities. 

Summary of Features: LT3518H

  • 150°C Maximum Junction Temperature
  • 3,000:1 True Color PWM™ Dimming Ratio
  • 2.3A, 45V Internal Switch
  • 100mV High-Side Current Sense
  • Open LED Protection
  • Adjustable Frequency: 250kHz to 2.5MHz
  • Wide Input Voltage Range:
    • Operation from 3V to 30V
    • Transient Protection to 40V
  • Operates in Boost, Buck & Buck-Boost Mode
  • Gate Driver for PMOS LED Disconnect
  • Constant-Current & Constant-Voltage Regulation
  • CTRL Pin Provides 10:1 Analog Dimming
  • Low Shutdown Current: <1µA
  • Tiny (4mm × 4mm) 16-Pin QFN Package

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