LT3755 Datasheet

• 3000:1 True Color PWM^™ Dimming
• Wide Input Voltage Range: 4.5V to 40V
• Output Voltage Up to 75V
• Constant-Current and Constant-Voltage Regulation
• 100mV High Side Current Sense
• Drives LEDs in Boost, Buck Mode, Buck-Boost Mode, SEPIC or Flyback Topology
• Adjustable Frequency: 100kHz to 1MHz
• Open LED Protection
• Programmable Undervoltage Lockout with Hysteresis
• PWM Disconnect Switch Driver
• CTRL Pin Provides Analog Dimming
• Low Shutdown Current: <1µA
• Programmable Soft-Start
• Thermally Enhanced 16-Lead QFN (3mm × 3mm) and MSOP Packages
• AEC-Q100 Qualified For Automotive Applications

• High Power LED
• Battery Chargers
• Accurate Current Limited Voltage Regulators

The LT3755 are DC/DC controllers designed to operate as a constant-current source for driving high current LEDs. They drive a low side external N-channel power MOSFET from an internal regulated 7.15V supply. The fixed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A ground referenced voltage FB 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 LT3755 sense output current at the high side of the LED string. High side current sensing is the most flexible scheme for driving LEDs, allowing boost, buck mode or buck-boost mode configuration. The PWM input provides LED dimming ratios of up to 3000:1, and the CTRL input provides additional analog dimming capability.