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Allegromicro公司的A8514是用于小型LCD背光的多輸出白光LED驅動器,集成了帶功率開關的電流模式升壓轉換器和四個電流沉.升壓轉換器能以80mA驅動多達48個LED,每串12個LED.LED沉并聯能提供更高電流,多達320mA.器件工作電壓5V-40V,開關頻率高達2.3MHz,每串LED匹配電流精度0.7% - 0.8%,PWM和模擬調光輸入,主要用在汽車信息娛樂系統,汽車儀表盤和汽車中心操控區.本文介紹了A8514主要特性和優勢, 方框圖,以及多種應用電路. The A8514 is a multi-output white LED driver for small-size LCD backlighting. It integrates a current-mode boost converter with internal power switch and four current sinks. The boost converter can drive up to 48 LEDs, 12 LEDs per string, at 80 mA. The LED sinks can be paralleled together to achieve even higher LED currents, up to 320 mA. The A8514 can operate with a single power supply, from 5 to 40 V, which allows the part to withstand load dump conditions encountered in automotive systems. The A8514 can drive an external P-FET to disconnect the input supply from the system in the event of a fault. The A8514 provides protection against output short and overvoltage, open or shorted diode, open or shorted LED pin, shorted boost switch or inductor, shorted FSET or ISET resistor, and IC overtemperature. A dual level cycle-by-cycle current limit function provides soft start and protects the internal current switch against high current overloads. The A8514 has a synchronization pin that allows PWM switching frequencies to be synchronized in the range of 580 kHz to 2.3 MHz. The high switching frequency allows the A8514 to operate above the AM radio band. A8514主要特性和優勢: • Wide input voltage range of 5 to 40 V for start/stop, cold crank and load dump requirements • Fully integrated LED current sinks and boost converter with 60 V DMOS • Sync function to synchronize boost converter switching frequency up to 2.3 MHz, allowing operation above the AM band • Excellent input voltage transient response • Single resistor primary OVP minimizes VOUT leakage • Internal secondary OVP for redundant protection • LED current of 80 mA per channel • Drives up to 12 series LEDs in 4 parallel strings • 0.7% to 0.8% LED to LED matching accuracy • PWM and analog dimming inputs • Provides driver for external PMOS input disconnect switch • Extensive protection against: ▫ Shorted boost switch or inductor ▫ Shorted FSET or ISET resistor ▫ Shorted output ▫ Open or shorted LED pin ▫ Open boost Schottky ▫ Overtemperature (OTP) A8514應用: LCD backlighting or LED lighting for: ▫ Automotive infotainment ▫ Automotive cluster ▫ Automotive center stack 
圖1.A8514方框圖
圖2.A8514采用P-MOSFET檢測和VIN接地短路保護的應用電路圖
圖3.A8514設計案例電路圖
圖4.A8514采用精密輸入電流檢測和VSENSE接地保護的SEPIC配置應用電路圖 詳情請見: http://www.allegromicro.com/en/Products/Part_Numbers/8514/8514.pdf |
