Allegromicro A8515高效白光LED驅動方案

Allegromicro A8515高效白光LED驅動方案
Allegromicro公司的 A8515是寬輸入電壓範圍高效多輸出白光LED(Wled)驅動器,輸入電壓從5V到40V,最大LED電流120mA,LED電流精度0.5%,LED到LED電流匹配0.5%,集成了60V DMOS開關,可驅動多達12串LED燈(24個LED燈),開關頻率高達2.25MHz,PWM調光,主要用在平板LCD屏以及平板視頻顯示屏.本文介紹了A8515主要特性和優勢, 功能方框圖以及多個典型應用電路.



Wide Input Voltage Range, High Efficiency Fault Tolerant LED Driver



The A8515 is a multi-output white LED (WLED) driver for LCD backlighting in consumer and industrial displays. It integrates a current-mode boost converter with an internal power DMOS switch and two current sinks. The boost converter can drive up to 24 LEDs: 12 LEDs per string at 120 mA. The LED sinks can be parallELed together to achieve higher LED currents, up to 240 mA. The A8515 can operate from a single power supply, from 5 to 40 V.



PWM dimming is implemented with an external PWM input signal. The PWM dimming pin is used to control the LED intensity by using pulse width modulation.



The low, 720 mV regulation voltage on the LED current sources reduces power loss and improves efficiency.



The A8515 is provided in a 16-pin TSSOP package (suffix LP) with an exposed thermal pad. It is lead (Pb) free, with 100% matte tin leadframe plating.



A8515主要特性和優勢:



? Wide input voltage range: 5 to 40 V



? Maximum LED current of 120 mA



? TSSOP-16 (LP) package; exposed pad offers best-in-class thermal performance



? Typical LED accuracy of 0.5%, and 0.5% for LED-to-LED matching



? Internal bias supply for single-supply operation (typically between VIN = 8 to 24 V)



? Integrated boost converter with 60 V DMOS switch with overvoltage protection (OVP)



? Drives up to 12 series LEDs in 2 parallel strings



? Single PWM pin interface for both PWM dimming and enable function



? Sync function to synchronize boost converter switching frequencies up to 2.25 MHz, this gives the designer the ability minimize component size



? Provides driver for external PMOS input disconnect switch



? Protection features:



? Open or shorted VLED pin protection



? Open Schottky protection



? Cycle-by-cycle current limit



? Overtemperature protection (OTP)



? Output short circuit protection



A8515應用:



? Desktop LCD flat panel displays (FPD)



? Flat panel video displays



? LCD TVs and monitors



圖1.A8515功能方框圖



圖2.A8515典型應用框圖



圖3.A8515設計案例應用電路圖



圖4.A8515升壓配置應用框圖



Typical application showing boost configuration, using current sensing and disconnect switch feature for an input of 12 V with an output to 18 LEDs (9 series LEDs in each of two strings) 120 mA current each LED



圖4.A8515 SEPIC配置應用框圖