Milpitas, Calif.—LEDs are increasingly the light source of choice for all the well-known reasons, but their use in fast-pulsing applications such as digital light projector (DLP) TVs has been thus far been limited not by the LEDs themselves, but by the ability of their drivers to switch them with the sufficiently fast rise and fall times needed. Linear Technology Corp maintains that their LT3743 IC is the first to solve this problem. The DC/DC switching power IC (100 kHz to 1 MHz) operates from a 5.5 to 36 V input, and can provide up to 20 A continuous from a 12 V source (80 W) and 40 W in pulsed mode (160 W), with efficiency reaching 95%. Other applications include driving architectural lighting and laser diodes.
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Key to the performance of the device is an topology with two compensation loops, which allows for fast PWM-based dimming over a 3000:1 ratio. The LT3743 also enables three-state current control for color mixing, key to better color fidelity in display applications. Current regulation accuracy is ±6% (worst case) with 2 μsec maximum recovery time between any current regulation states.
The thermally enhanced device does not require any additional heat sinking, and has shutdown current less than 1 μA. Outputs are protected against open loads as well as short, and the LT3743 includes output voltage regulation, overcurrent protection, and a thermal derating circuit. The vendor cautions that designers incorporating this part need to understand the implications of these high current levels, including IR drop, switching large amounts of current and other unpleasant realities when testing an overall design. For example, a standard DC-current probe introduces enough inductance to slow down the output current rise and fall times, so they suggest use of a currant-sense resistor in series with the load during test phase.—Bill Schweber
Packaging, price, and availability : The LT3743 is available from stock, in either a 28-lead 4×5 QFN package or a thermally enhanced TSSOP-28 package. Pricing starts at $4.80 in 1000-piece lots.
For more information : contact Linear Technology Corp., http://www.linear.com.