The device's internal PWM dimming generator makes it ideal for controlling high-current LEDs and also incorporates features suitable for charging batteries and supercapacitors. The LT3954's input voltage range of 4.5V to 40V is suitable for a wide variety of applications, including automotive, industrial, and architectural lighting.
Utilizing an internal 5A, 40V N-channel MOSFET, the LT3954 can drive up to eight 650mA white LEDs from a nominal 12V input, delivering over 20W. It incorporates high-side current sensing, enabling its use in boost, buck, buck-boost, or SEPIC configurations. The LT3954 can achieve efficiencies exceeding 95% in boost mode, eliminating the need for an external heatsink. A frequency adjustment pin allows the user to program the frequency between 100kHz and 1MHz, optimizing efficiency and minimizing the size and cost of external components. Combined with its 5mm x 6mm QFN package, the LT3954 offers a very compact, high-power LED control solution.
The LT3954 features an internal PWM generator that provides a dimming ratio of up to 25:1, or it can utilize an external PWM signal, achieving a dimming ratio of up to 3,000:1. For less demanding dimming requirements, the CTRL pin can be used to provide an analog dimming range of 10:1. Its fixed-frequency current-mode architecture offers stable operation over a wide range of supply and output voltages. Output short-circuit protection and open-LED protection enhance system reliability. The LT3954's ground-referenced voltage pin (FB) serves as an input for various LED protection functions and allows the converter to operate as a constant voltage source for load applications.
The LT3954EUHE is supplied in a 5mm x 6mm, 36-pin QFN package. The starting price is $3.60 per unit. A Grade I version, designated LT3954IUHE, is also available with an extended temperature range.
Main features:
• 3000:1 True Color PWM™ Dimming for LEDs
• Wide VIN Range: 4.5V to 40V
• Rail-to-Rail Current Sensing Range: 0V to 40V
• Internal 40V/5A Switch
• Programmable PWM Dimming Signal Generator
• Constant Current (±3%) and Constant Voltage (±2%) Regulation
• Precise Analog Dimming
• Controls LEDs in Boost, SEPIC, CUK, Buck, Buck-Boost, or Flyback configurations
• Output Short Circuit Protection
• Open LED Protection and Warning
• Adjustable Switching Frequency: 100kHz to 1MHz
• Programmable VIN Undervoltage Lockout with Hysteresis
• C/10 Indicator for Battery Chargers
• Low Turn-Off Current
• Thermally Enhanced 5mm × 6mm QFN-36 Package
