LT8376 Step-Down LED Driver with Silent Switcher®

ADI's LT8376 monolithic, synchronous, step-down DC/DC converter utilizes fixed-frequency, peak current control and provides PWM dimming for a string of LEDs. Analog voltage or the duty cycle of pulses at the CTRL pin program the LED current. A resistor divider to the FB pin can set the output voltage limit.

The LT8376 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 unavailable. An external resistor at the RT pin or an external clock at the SYNC/SPRD pin program the switching frequency from 200 kHz to 2 MHz. The frequency varies from 100% to 125% to reduce EMI with the optional spread spectrum frequency modulation enabled.

Additional features include 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. The LT8376 utilizes the proprietary Silent Switcher technology for very low EMI.

Evaluation board EVAL-LT8376-AZ is a 60 V, 2 A synchronous buck LED driver featuring the LT8376. The EVAL-LT8376-AZ drives a single string of LEDs up to 36 V at 1.5 A when V_IN is between 43 V and 57 V. The board has undervoltage lockout (UVLO) set at 40 V with 2 V hysteresis for turn-on. It runs at 350 kHz switching frequency and features optional spread spectrum modulation (SSFM), which modulates its switching frequency from f_SW to f_SW + 25% to reduce EMI emissions when enabled.