Allegromicro A8515高效白光LED驱动方案
Allegromicro公司的 A8515是宽输入电压范围高效多输出白光LED(Wled)驱动器,输入电压从5V到40V,最大LED电流120mA,LED电流精度0.5%,LED到LED电流匹配0.5%,集成了60V DMOS开关,可驱动多达12串LED灯(24个LED灯),开关频率高达2.25MHz,PWM调光,主要用在平板LCD屏以及平板视频显示屏.本文介绍了A8515主要特性和优势, 功能方框图以及多个典型应用电路.
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主要特性和优势:
? 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应用:
? Desktop LCD flat panel displays (FPD)
? Flat panel video displays
? LCD TVs and monitors
图1.A8515功能方框图
图2.A8515典型应用框图
图3.A8515设计案例应用电路图
图4.A8515升压配置应用框图
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
图4.A8515 SEPIC配置应用框图
