Datasheet LT3795 (Analog Devices)

LT3795 110V LED Controller with Spread Spectrum Frequency Modulation
FEATURES DESCRIPTION
n
3000:1 True Color PWM™ Dimming
The LT®3795 is a DC/DC controller designed to regulate a n
Wide Input Voltage Range: 4.5V to 110V
constant-current or constant-voltage and is ideal for driv- n
Input and Output Current Reporting
ing LEDs. It drives a low side external N-channel power n
PMOS Switch Driver for PWM and Output Disconnect
MOSFET from an internal regulated 7.7V supply. The fixed n
Internal Spread Spectrum Frequency Modulation
frequency and current mode architecture result in stable n ±2% Constant Voltage Regulation operation over a wide range of supply and output voltages. n ±3% Constant Current Regulation: 0V ≤ VOUT ≤ 110V Spread spectrum frequency modulation (SSFM) can be n Programmable Input Current limit activated for improved electromagnetic compatibility (EMC) n CTRL Inputs Linearly Adjust LED Current performance. The ground referred voltage FB pin serves as n Adjustable Frequency: 100kHz to 1MHz the input for several LED protection features, and also al- n Programmable Open LED Protection with OPENLED Flag lows the converter to operate as a constant-voltage source. n Short-Circuit Protection and SHORTLED Flag The maximum output current is set by an external resistor, n Programmable Undervoltage Lockout with Hysteresis and the output current amplifier has a rail-to-rail common n Soft-Start with Programmable Fault Restart Timer mode range. The LT3795 also includes a separate input n C/10 Detection for Battery Charging current sensing amplifier that is used to limit input current. n Available in 28-Lead TSSOP Package The TG pin inverts and level shifts the PWM signal to drive the gate of the external PMOS. The PWM input provides
APPLICATIONS
LED dimming ratios of up to 3000:1, and the CTRL inputs n High Power LED, High Voltage LED provide additional analog dimming capability. n Battery Chargers L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and True Color PWM is a trademark of Linear Technology Corporation. All other trademarks are the n Accurate Current Limited Voltage Regulators property of their respective owners. Protected by U.S. Patents, including 7199560, 7321203, 7746300.
TYPICAL APPLICATION Short-Circuit Robust Boost LED Driver with Spread Spectrum Frequency Modulation Efficiency vs VIN
VIN 15mΩ 22µH 100 8V TO 60V 110V (TRANSIENT) 2.2µF 2.2µF 63V OVLO 499k ×3 1M ×4 95 115k EN/UVLO VIN IVINP IVINN 90 GATE OVLO 13.3k SENSE 12.4k 85 CTRL1 15mΩ CTRL2 EFFICIENCY (%) 80 V LT3795 REF GND PWM PWM FB IVINCOMP 75 ISP 10nF 620mΩ RAMP 70 INTVCC 6.8nF 0 10 20 30 40 50 60 ISN 100k 100k VIN (V) TG 3795 TA01b OPENLED OPENLED SHORTLED SHORTLED INTVCC INTVCC V 4.7µF C RT ISMON SS 87V LED 31.6k 400mA 10k 0.1µF 0.1µF 250kHz 6.8nF 3795 TA01a 3795fc For more information www.linear.com/LT3795 1 Document Outline Features Applications Typical Application Description Absolute Maximum Ratings Pin Configuration Order Information Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Applications Information Typical Applications Package Description Revision History Typical Application Related Parts