Universal High Brightness LED Driver

The SQ9911 is pin-to-pin compatible with SQ9910 for better system performace and cost. SQ9911 adds Soft Start to reduce input surge current during cold start. It typically waits for 400 μS before normal PWM function starts. SQ9911 also adds pseudo-random oscillator hopping function (Spread Sprectrum) to reduce EMI emmission so that input EMI filter cost can be reduced. Typical oscillator hopping range is approximately 8% around base frquency set by ROSC. SQ9911 allows efficient operation of High Brightness (HB) LEDs from voltage sources ranging from 85VAC up to 265VAC . The SQ9911 controls an external MOSFET at fixed switching frequency up to 300kHz. The LED string is driven at constant current rather than constant voltage, thus providing constant light output and enhanced reliability. The output current can be programmed between a few milliamps and up to more than 1.0A. SQ9911A allows wide range of external MOSFET which has lower RDSON at higher VGS.

FEATURES

● Pin-to-pin compatible with SQ9910/SQ9910A

● >90% Efficiency

● Universal rectified 85 to 265VAC input range 

● Constant-current LED driver

● Applications from a few mA to more than 1A Output

● LED string from one to hundreds of diodes

● PWM Low-Frequency Dimming via Enable pin

● Input voltage surge ratings up to 500V

● Power-on sequence control and Soft Start

● Spread Spectrum to reduce EMI filter cost

● Internal Thermal Protection (OTP)

● 7.5V MOSFET drive – SQ9911

10V MOSFET drive – SQ9911A

TYPICAL APPLICATIONS 

● DC/DC or AC/DC LED Driver application 

● RGB Backlighting LED Driver

● Back Lighting of Flat Panel Displays 

● General purpose constant current source

● Signage and Decorative LED Lighting

APPLICATION CIRCUIT