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
- 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 VIN UVLO with Hysteresis
- C/10 Indication for Battery Chargers
- Low Shutdown Current: <1μA
- Thermally Enhanced 5mm × 6mm QFN Package
The LT3955 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.
- High Power LEDs
- Output Short-Circuit Protected Boost
- Battery and SuperCap Chargers
- 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)
Demonstration circuit 2020A is a 60VIN, 80VOUT LED driver. It generates its own PWMOUT waveform from its internal PWM generator for accurate PWM dimming with up to 33:1 brightness ratio. It accepts an input voltage from 5V to 60V and drives up to 67V of LEDs at 300mA (when PVIN is less than VLED). DC2020A features both PWM and analog dimming of the LED string. It has an OPENLED flag that indicates when the LED string has been removed. DC2020A features high efficiency at 350kHz switching frequency. At high LED string voltages up to 67V and 300mA of LED current, the single switch controller has 92% efficiency. The LT3955 has an internal 80V, 3.5A switch that simplifies the schematic and layout.
Tools & Simulations
LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.
To launch ready-to-run LTspice demonstration circuits for this part:
Step 1: Download and install LTspice on your computer.
Step 2: Click on the link in the section below to download a demonstration circuit.
Step 3: If LTspice does not automatically open after clicking the link below, you can instead run the simulation by right clicking on the link and selecting “Save Target As.” After saving the file to your computer, start LTspice and open the demonstration circuit by selecting ‘Open’ from the ‘File’ menu.
Models for the following parts are available in LTspice:
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Sample & Buy
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Pricing displayed is based on 1-piece. The USA list pricing shown is for budgetary use only, shown in United States dollars (FOB USA per unit), and is subject to change. International prices may vary due to local duties, taxes, fees and exchange rates.