Features and Benefits
- True Color PWM™ Dimming Delivers Up to 5000:1 Dimming Ratio (In Boost Configuration)
- LED Current Regulation with High-Side Sense
- VADJ Pin Accurately Sets LED Current Sense Threshold Over Range 10mV to 120mV
- Four Independent Driver Channels with 1.5A, 36V Internal NPN Switches
- Frequency Adjust Pin: 200kHz to 2MHz
- High Efficiency Conversion = Up to 96%
- Open LED Protection
- Low Shutdown Current < 10μA
- Wide VIN Range: 2.8V to 16V
- Thermally Enhanced, 38-Lead, 5mm × 7mm QFN Package
The LT3476 is a quad output DC/DC converter designed to operate as a constant-current source for driving high current LEDs. A ﬁxed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A frequency adjust pin allows the user to program switching frequency between 200kHz and 2MHz to optimize efﬁciency and external component size.
The LT3476 senses output current at the high side of the LED. High side current sensing is the most ﬂexible scheme for driving LEDs, allowing buck, boost or buckboost conﬁgurations. Each current monitor threshold is trimmed to within 2.5% at the full scale of 105mV. With an external sense resistor, the user programs the output current range of each channel. Each of the four regulators is independently operated by that channel’s PWM signal. This PWM feature allows precise adjustment of the color mixing or dimming ratio of the LED source. Dimming ratios up to 1000:1 can be achieved.
- RGGB Lighting
- Automotive and Avionic Lighting
- TFT LCD Backlighting
- Constant-Current Sources
Product Lifecycle Production
At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.
Evaluation Kits (1)
Demonstration circuit 976 is a Quadruple High Power LED Driver in Buck Mode featuring the LT3476EUHF. The LT3476 is a quad output, multitopology DC/DC converter designed to operate as a current source for driving high current LEDs. Each of the four regulators on the demo circuit is independently operated. The VIN power supply for the IC ranges from 2.8V to 16V. The PVIN power supply for the buck regulators ranges up to 33V.
On the demo circuit, the default current for each output channel is 350mA but it can be adjusted up to 1.05A via resistor dividers at the VADJ pins. The output current should not exceed the rated current of the LEDs used. If 1W LEDs, such as the Lumileds Luxeon LEDs, are used, 350mA current is the maximum. 1A output current is reserved for 3W LEDs, such as Luxeon III.
The input voltage is limited by the CAP pin overvoltage protection threshold. As a result, each channel of the demo circuit can drive up to 27V total LED voltage.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.
Sample & Buy
The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.