Three-output LED driver solution based on LT3496

This article introduces the main features, block diagram, various application circuits of LT3496 and the main features and circuit diagram of LT3496EUFD evaluation board. LT3496 is a three-output DC/DC converter of Linear Corporation, which can work as a constant current and is very suitable for driving LEDs. The adjustable switching frequency is from 330kHz to 1MHz, the dimming ratio is up to 3000:1, and it can work in buck, boost and buck-boost modes. It has three independent drivers with built-in 750mA/45V switches and open-circuit LED protection. It is mainly used in RGB lighting, automotive and military aircraft lighting, billboards and large displays, and constant current sources. The LTR3496 is a triple output DC/DC converter designed to operate as a constant-current source and is ideal for driving LEDs. The LT3496 works in buck, boost or buckboost mode. The LT3496 uses a fixed frequency, current mode architecture resulting in stable operation over a wide range of supply and output voltages. A frequency adjust pin allows the user to program switching frequency between 330kHz and 2.1MHz to optimize efficiency and external component size. The LT3496 supports 30 00:1 dimming control on each channel. Each of the three regulators is independently operated by that channel's PWM signal. The PWM feature allows precise adjustment of the color mixing or dimming ratio of the LED source. Each of the three channels has a built-in gate driver to drive an external LED-disconnect P-channel MOSFET, allowing high dimming range. The output current range of each channel of the LT3496 is programmed with an external sense resistor. The CTRL pins are used to adjust the LED currents either dim for analog ming or overtemperature protection. LT3496 Key Features: True Color PWM™ Dimming Delivers Up to 3000:1 Dimming Ratio Built-In Gate Driver for PMOS LED Disconnect Three Independent Driver Channels with 750mA, 45V Internal Switches Operates in Buck, Boost, Buck-Boost Modes CTRL Pin Accurately Sets LED Current Sense Threshold Over a Range of 10mV to 100mV Adjustable Frequency: 3 30kHz to 2.1MHz Open LED Protection Wide VIN Supply Range: Operation from 3V to 30V Transient Protection to 40V Surface Mount Components 28-Lead (4mmx 5mm) QFN and TSSOP Packages LT3496 Applications: RGB Lighting Billboards and Large Displays Automotive and Avionic Lighting Constant-Current Sources Figure 1. LT3496 block diagram (boost configuration) Figure 2. LT3496 High Dimming Ratio Triple Output LED Power Supply Figure 3. LT3496 Buck Mode Lowest BOM LED Driver Figure 4. LT3496 Triple Output 100mAx10 LED Driver Figure 5. LT3496 Dual Boost LED Driver Figure 6. LT3496 Triple Output Boost 20mAx8 LED Driver Figure 7. LT3496 Buck-Boost Mode 30mAx6 LED Driver Figure 8. LT3496 Triple Output Buck Mode LED Driver with Open Circuit LED Protection Figure 9. LT3496 Triple Output Buck Mode 3x500mA LED String Driver Figure 10. LT3496 Triple Output Boost Mode 200mA LED Driver Figure 11. LT3496 Triple Output Buck-Boost Mode LED Driver LT3496EUFD Evaluation Board



































































Demonstration circuit 986 is a Triple Step-Dow n LED Driver featuring the LT3496EU FD. The LT3496 is a triple output DC/DC converter designed to operate as current sources for driving high current LEDs. O n the demo board, the default current for each output channel is 500mA. Setting CTR L voltage to be less than 1V w ill control the current sense voltage to be one-tenth of CTR L voltage, therefore, reduce the LED current. The output current should not exceed the rated cur¬rent of the LEDs used. The LED current thermal de-rating should be considered to protect the LEDs. The maximum voltage of an LED string the demo board can drive is limited by the duty cycle and the input voltage of the LT3496. The demo board default switching frequency is 2.1M H z. At this frequency, the maximum duty cycle is 70% (M IN ). Lower the switching frequency results in higher maximum duty cycle. The maximum power input voltage (PVIN) is 45V. As a result, each channel of the demo board can drive up to ~31V total LED voltage. Adjustable switching frequency allows optimization of the efficiency and the external component size. At 2.1M H z, 93% efficiency can be achieved at 500mA with minimum solution size. Each of the three regulators on the demo board is in¬dependently operated. The PWM dimming feature of the LT3496 allow s True Color PWM dimming with the dimming ratio of 5000:1. Additional analog dimming is possible. The LT3476 datasheet gives complete description of the part, operation and application information. The datasheet must be read in conjunction with this quick start guide for working on or modifying the demo circuit 986.

图12。LT3496EUFD 评估板电路图