Analog Devices LT3922-1

Description

The LTR3922-1 is a monolithic, synchronous, step-up DC/DC converter that utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs. The LED current is programmed by an analog voltage or the duty cycle of pulses at the CTRL pin. The LT3922-1 will maintain ±2% current regulation through an external sense resistor over a wide range of output voltages.The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an external clock applied at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI. The LT3922-1 also includes a driver for an external high side PMOS for PWM dimming and an internal PWM signal generator for analog control of PWM dimming. When an external signal is available, the LT3922-1 can perform 25,000:1 PWM dimming with 100Hz PWM pulses.Additional features include an accurate external reference voltage for use with the CTRL and PWM pins, an LED current monitor, an accurate EN/UVLO pin threshold, open-drain fault reporting for open-circuit and short-circuit load conditions, and thermal shutdown.

Features

• ±2% LED Current Regulation
• ±2% Output Voltage Regulation
• 25,000:1 PWM Dimming at 100Hz
• 128:1 Internal PWM Dimming
• Spread Spectrum Frequency Modulation
• Silent Switcher® Architecture for Low EMI
• Operates in Boost, Buck Mode and Buck-Boost Mode
• 2.8V to 36V Input Voltage Range
• Up to 34V LED String Voltage
• 2.3A, 40V Internal Switches
• 200kHz to 2MHz Switching Frequency with SYNC
• Analog or Duty Cycle LED Current Control
• Open/Short LED Protection and Fault Indication
• Thermally Enhanced 28-Lead (4mm × 5mm) QFN

Typical applications

• Automotive and Industrial Lighting
• Machine Vision

More information

• Datasheet