STEVAL-ILL023V1 STMicroelectronics

STEVAL-ILL023V1 Demonstration board: high-efficiency switching LED driver for high-current LEDs based on the L6726A Data Brief Features Input voltage Vin: 8 V to 18 V Output voltage (with Vin = 18 V): 2.5 V to 14 V Output current I : 1 A / 1.5 A / 2.8 A LED Analog dimming (with I = 0 A): 0 V to 2.5 V LED Low level PWM signal: 0 V High level PWM signal: 2.8 V to 3.8 V (typ: 3.3 V) Duty cycle (at fdim = 200 Hz): 0% to 99 % Efficiency (with Vin = 18 V and Vout = 12.6 V): 94.8 % Description Rapid advances in LED technology has led to increases in their output current capabilities in STEVAL-ILL023V1 recent years. 0.350 A LEDs, for example, were soon followed by 0.7 A LEDs, and then 1 A devices appeared shortly thereafter. Currently, LEDs with currents as high as several amps are present on the market. However, these high currents increase the requirements of the driving circuitry of the LEDs, particularly in terms of efficiency. The STEVAL-ILL023V1 demonstration board is based on the L6726A single phase PWM controller, with two external MOSFETS for synchronous rectification. Designed for 2.8 A LEDs (1-3 in a series string), the main benefit of the solution is its exceptional efficiency. Ease of dimming and scalability to even higher currents are additional advantages of the design. The solution is also much safer with regard to border conditions, since the current limit is based solely on the selection of the MOSFETS. February 2009 Rev 1 1/4 For further information contact your local STMicroelectronics sales office. www.st.com 4Circuit schematic STEVAL-ILL023V1 1 Circuit schematic Figure 1. STEVAL-ILL023V1 schematic diagram 2/4 Vcc18V CN1 1 D2 2 U1 L78L0606AC 3 C1 3 1 Vcccc6V IN OUT 22uF 8-18V GNGND C4 C6 1N4148 K375A 10uF 100n00nF R6 10R U2 L6726A 1 Boooot Q1 Boooot C7 STS8DNH3LL 100n0nF P1 FB 6 R7 FB R4 2 Ugate 2 Ugate 4k7 7 C8 COMP 8 2R2 4.7uF R3 Phase PWM Comp OUOUT L1 4 Phase OUOUT-A 4k7 Lgate 3 R1 6 PWM Inductor 2 5 C2 R2 10uH 62k 1 4 R8 Vref 47700pF 1k1 3 C9 Lgate 4 OUOUT-K 2 R5 D3 22uF C5 1 6k8 C3 2R2 STPS1L30M D1 82nF 1000nnF TS821 R9 R10 R14 R15 R16 0R56 0R56 0R56 0R3 0R3 GGNND 2 3 5 GGNND Vcc 3 5 1 8 6 7 1 2 3