New Industry Products

36V, 2A Synchronous Buck-Boost Converter and LED Driver

October 28, 2019 by Paul Shepard

The LT3942 from Analog Devices is a monolithic 4-switch synchronous buck-boost LED driver. The driver can regulate the LED string current up to 34V with input voltages above, below, or equal to the output voltage. The proprietary peak-buck peak-boost current mode control scheme allows adjustable and synchronizable 300kHz to 2MHz fixed frequency operation, or internal 25% triangle spread spectrum operation for low EMI.

With 3V to 36V input, 0V to 36V output and seamless low-noise transitions between operation regions, the LT3942 is designed for LED driver applications in automotive, industrial and battery-powered systems. The schematic above illustrates a typical application with the LT3942 used in a 93% efficient, 12W (12V, 1A) 2MHz buck-boost LED driver circuit.

The LT3942 provides LED current regulation with up to 128:1 internal and 5000:1 external pwm dimming using an optional high-side PMOS switch. The CTRL pin provides flexible 20:1 analog dimming with ±2.5% LED current regulation at 100mV full scale. Robust fault protection detects an open or short LED condition, during which the LT3942 retries, latches off, or keeps running.

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Summary of Features and Specifications

  • 4-Switch Single Inductor Architecture Allows VIN Above, Below or Equal to VOUT
  • Proprietary Peak-Buck Peak-Boost Current Mode
  • 3V to 36V Input Voltage Range
  • 0V to 36V Output Voltage Range
  • ±1.5% Output Voltage Regulation
  • ±3% LED Current Regulation
  • 5000:1 External and 128:1 Internal PWM Dimming
  • Rail-to-Rail LED Current Sense and Monitor Output
  • Open and Short LED Protection with Fault Reporting
  • 300kHz to 2MHz Fixed Switching Frequency with External Frequency Synchronization
  • Flicker-Free Spread Spectrum for Low EMI
  • Available in 28-Lead QFN (4mm × 5mm)