Features and Benefits
- 3000:1 True Color PWM™ Dimming for LEDs
- Wide VIN Range: 4.5V to 60V
- Rail-to-Rail Current Sense Range: 0V to 80V
- Programmable PWM Dimming Signal Generator
- Constant Current (±3%) and Constant-Voltage (±2%) Regulation
- Analog Dimming
- Drives LEDs in Boost, SEPIC, Inverting, Buck Mode, Buck-Boost Mode, or Flyback Configuration
- Output Short-Circuit Protected Boost
- Open LED Protection
- Adjustable Switching Frequency: 100kHz to 1MHz
- Programmable VIN UVLO with Hysteresis
- C/10 Indication for Battery Chargers
- Low Shutdown Current: <1μA
- Thermally Enhanced 16-Lead MSOP Package
- Open LED Status Pin (LT3761)
- Frequency Synchronization (LT3761-1)
The LT3761/LT3761-1 is a DC/DC controller designed to operate as a constant-current source and constant-voltage regulator. It features a programmable internal PWM dimming signal. The LT3761/LT3761-1 is ideally suited for driving high current LEDs, but also has features to make it suitable for charging batteries and supercapacitors. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A voltage feedback pin serves as the input for several LED protection features, and also makes it possible for the converter to operate as a constant-voltage source. A frequency adjust pin allows the user to program the frequency from 100kHz to 1MHz to optimize efficiency, performance or external component size. The LT3761-1 can be synchronized to an external clock. The LT3761/LT3761-1 senses output current at the high side or at the low side of the load. The PWM input can be configured to self-oscillate at fixed frequency with duty ratio programmable from 4% to 96%. When driven by an external signal, the PWM input provides LED dimming ratios of up to 3000:1. The CTRL input provides additional analog dimming capability.
The LT3761/LT3761-1 senses output current at the high side or at the low side of the load. The PWM input can be configured to self-oscillate at fixed frequency with duty ratio programmable from 4% to 96%. When driven by an external signal, the PWM input provides LED dimming ratios of up to 3000:1. The CTRL input provides additional analog dimming capability.
|LT3761A||Higher PWM Dimming Accuracy at Lower LED Current Levels|
|LT3761||Open LED Status Pin|
- High Voltage LED Strings >100V with Ground Referred Current Sense
- Grounded Anode LEDs
- Accurate Current Limited Voltage Regulators
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)
DC1772A is a high voltage LED controller with internal PWM dimming. It generates its own PWMOUT waveform for accurate PWM dimming with up to 25:1 brightness ratio. It accepts an input voltage from 8V to 60V (8V UVLO and 9.1V rising turn-on), and drives up to 60V of LEDs at 1A (when PVIN is less than VLED).
DC1772A features both PWM and analog dimming of the LED string. It has an OPENLED flag that indicates when the LED string has been removed. DC1772A features high efficiency at 350kHz switching frequency. At high LED string voltages up to 60V and 1A of LED current, the single switch controller has 94% efficiency. The open LED overvoltage protection uses the IC’s constant voltage regulation loop to regulate the output to approximately 69.8V if the LED string is opened although it may reach 74V peak during transient from running LEDs to open. The maximum LED string voltage can be raised from 60V to 65V (or higher) with a simple charge of feedback resistors.
Tools & Simulations
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Models for the following parts are available in LTspice:
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