Features

• 3000:1 True Color PWM™ Dimming for LEDs
• Wide V_IN Range: 4.5V to 60V
• Rail-to-Rail Current Sense Range: 0V to 80V
• Internal 80V/3.5A Switch
• Programmable PWM Dimming Signal Generator
• Constant Current (±3%) and Constant-Voltage (±2%) Regulation
• Accurate Analog Dimming
• Drives LEDs in Boost, SEPIC, CUK, Buck Mode,
• Buck-Boost Mode, or Flyback Configuration
• Output Short-Circuit Protected Boost
• Open LED Protection and Reporting
• Adjustable Switching Frequency: 100kHz to 1MHz
• Programmable V_IN UVLO with Hysteresis
• C/10 Indication for Battery Chargers
• Low Shutdown Current: <1μA
• Thermally Enhanced 5mm × 6mm QFN Package

Typical Application

Description

The LT®3955 is a DC/DC converter designed to operate as a constant-current source and constant-voltage regulator. It features an internal low side N-channel MOSFET rated for 80V/3.5A. The LT3955 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 LT3955 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.