Analog Devices LT3932 | Demoboard Design Note DN570

Description

The LT®3932 , featuring the Silent Switcher®architecture to minimize EMI/EMC emissions, utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs. The LED current is programmed by an ana¬log voltage or the duty cycle of pulses at the CTRL pin. An output voltage limit can be set with a resistor divider to the FB pin. The switching frequency is programmable from 200kHz to 2MHz by an external resistor at the RT pin or by an exter¬nal clock at the SYNC/SPRD pin. With the optional spread spectrum frequency modulation enabled, the frequency varies from 100% to 125% to reduce EMI. The LT3932 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 not available. The LT3932-1 permits higher dimming ratios. Additional features include an LED current monitor, an accurate EN/UVLO pin threshold, open-drain fault report¬ing for open-circuit and short-circuit load conditions, and thermal shutdown.

Features

• ±1.5% LED Current Regulation
• ±1.2% Output Voltage Regulation
• 5000:1/10000+:1 PWM Dimming at 100Hz(LT3932/LT3932-1)
• 128:1 Internal PWM Dimming
• Spread-Spectrum Frequency Modulation
• Silent Switcher® Architecture for Low EMI
• 3.6V to 36V Input Voltage Range
• 0V to 36V LED String Voltage
• 200kHz to 2MHz with SYNC Function
• 99.9% Maximum Duty Cycle
• 20:1 Analog or Duty Cycle LED Current Control
• Open/Short LED Protection and Fault Indication
• Accurate LED Current Sense with Monitor Output
• Programmable UVLO
• Thermally Enhanced 28-Pin (4mm × 5mm) QFN

Typical applications

• Automotive Lighting
• Industrial and General Purpose Lighting
• Machine Vision Systems

More information

• Datasheet
• IC product information