LED770x LED drivers New monolithic step-up family driving LEDs for backlighting and lighting The LED770x family features two monolithic, high-efficiency LED drivers specifically designed to supply LED arrays used in the backlighting of LCD panels and general lighting. The drivers consist of a boost converter and six integrated PWM-dimmable current generators that give excellent dimming performance, and are housed in small VFQFPN4x4-24L packages. Additional flexibility is guaranteed by a wide range of adjustable protection systems and thresholds, together with complete and flexible fault management, a wide input voltage range (from 4.5 V up to 36 V) and high switching frequency, to reduce size and cost of the total application. Key features QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ QQ 4.5 to 36 V input voltage range Six rows of up to 10 WLEDs each, with adjustable maximum current: QQ 30 mA max for LED7706 QQ 85 mA max for LED7707 Internal power MOSFET Housed in compact QFN 4x4 24L package 200 kHz to 1 MHz switching frequency External synchronization for multi-device applications Row disable option Soft-start, programmable OVP, thermal shutdown Ceramic output capacitor supported Parallelable rows ±2 % current matching LED failure (open and short circuit) detection Less than 500 µs minimum dimming time (1% minimum dimming duty-cycle at 20 kHz) Less than 10 µs for LED7707 www.st.com/powermanagement Key benefits QQ QQ QQ QQ Monolithic and flexible solution High efficiency Superior dimming capability Complete and flexible fault management Targeted applications QQ QQ QQ Consumer: mid to large size LCD TVs, monitors, portable entertainment Automotive: navigation displays and dashboards Industrial: lighting, displays, e-signage Application diagram VIN = 4.5 V to VOUT VOUT = up to 36 V +5 V AVCC VIN LX SLOPE OVSEL SWF LDO5 ROW1 BILIM ROW2 RILIM ROW3 LED770x SS ROW4 COMP ROW5 SGND DIM Dimming ROW6 FAULT EN SYNC MODE PGND Enable Fault LED770x simplified application circuit Device description The LED770x is a monolithic LED driver family for backlighting of LCD panels and lighting. The two devices consist of a boost converter and six integrated PWM-dimmable current generators. The boost section is based on a constant switching-frequency, peak current-mode architecture. The devices keep the lowest row’s voltage regulated at the internal reference voltage, and adapt the boost output voltage to reduce power losses across the current generators. The boost-converter switching frequency is fixed at 630 kHz. This is a good compromise in terms of efficiency, size and cost of the power elements and of the overall application, but it can also be set anywhere in the 200 kHz to 1 MHz range by simply connecting a resistor to SGND, if more flexibility is required. The LED770x devices, with their input voltage range from 4.5 V up to the output voltage, cover the most common voltage buses (5 V, 12 V and 24 V). In addition, an internal LDO supplies the internal circuitry of the device and is capable to deliver up to 40 mA. The generators can be externally programmed by using a single resistor to sink up to 30 mA or 85 mA (LED7707), and can be dimmed via a PWM signal. The devices detect and manage open and shorted LED faults, and leave unused rows floating, keeping extremely high flexibility for the final application. Basic protection (adjustable output overvoltage, adjustable internal MOSFET overcurrent and thermal shutdown) are also provided. LED770x product table Part number Vin (V) Vout (V) Irows (mA) Rows Fsw (kHz) Package LED7706 4.5 to 36 Up to 36 Up to 30 6 Min dimming time Max LEDs per row 500 ns 10 (white) 200 to 1000 VFQFPN4x4-24L LED7707 4.5 to 36 Up to 36 Up to 85 6 10 μs 10 (white) 200 to 1000 VFQFPN4x4-24L Evaluation boards Description Related documentation STEVAL-ILL020V1 Part number LED7706: 6-row, 30 mA LED driver with boost converter AN2809 STEVAL-ILL021V1 LED7707: 6-row, 85 mA LED driver with boost converter AN2810 © STMicroelectronics - February 2010 - Printed in Italy - All rights reserved The STMicroelectronics corporate logo is a registered trademark of the STMicroelectronics group of companies. All other names are the property of their respective owners. For more information on ST products and solutions, visit www.st.com Order code: FLED770X0210