High-Side Sensing CCM Buck Controller for LED Drivers

The FL7760 from ON Semiconductor is a constant-current step-down CCM controller for wide output power LED lighting applications. The FL7760 adapts hysteretic reference architecture that accurately regulates LED current by sensing voltage across an external high side sense resistor.

This control scheme can stabilize LED current against input voltage and output load transient condition and implement optimal pwm and analog dimming control. Time delay control method widens analog dimming range down to less than 5%.

FL7760 has low 200 mV reference voltage to maximize system efficiency and high frequency driving capability so that system profile can be minimized in wide scale power ranges.

Application Schematic for Analog or PWM Dimming (click on schematic to enlarge)

The FL7760 implements pwm and analog dimming together through a DIM pin and provides thermal shutdown (TSD), and under-voltage lockout (UVLO) protections.

Features include:

• Wide Input Range (8- to 60-Vdc)
• Continuous Conduction Mode Operation
• Hysteretic LED Current Control
• Wide analog dimming range down to 5%
• Wide PWM dimming duty range to 0.2% at 2 kHz PWM frequency
• High switching frequency up to 1 MHz
• High source / sink current of 1.5 A / 2.5 A
• Cycle-by-Cycle Peak Current Limit
• Low Operating Current (300 uA)
• Low Stand-by Current (240 uA)