基于MIC3263設計的六路LED驅動技術

MIC3263是Micrel公司的六路白光LED(WLED)驅動器,采用高效的PWM升壓開關技術,最適合用于恒流WLED背光驅動.每路電流的匹配在±3%,電流在15mA到30mA可編程.輸入電壓從6V到40V,每路可驅動多達10個WLED,調光比在1%-100%之間,效率高達90%,主要用在筆記本電腦,LCD屏和監視器,多媒體播放器,導航設備,游戲機等.本文介紹MIC3263主要特性,功能方框圖,典型應用電路以及MIC3263評估板電路圖和材料清單(BOM).

白光LED的PWM驅動：http://www.elecfans.com/soft/70/2010/2010021168002.html

MIC3263; Six-Channel WLED Driver for Backlighting Applications with Flicker-Free Dimming

The MIC3263 is a high-efficiency Pulse Width Modulation (PWM) boost switching regulator that is optimized for constant-current WLED driver backlighting applications. The MIC3263 drives six channels of up to ten WLEDs per channel. Each channel is matched in current to within ±3% for constant brightness across the screen and can be programmed from 15mA to 30mA.

The MIC3263 provides a very flexible dimming control scheme with better accuracy and noise immunity. The dimming frequency can be set to any value between 100Hz and 20kHz by an external resistor. The dimming ratio is determined by the duty cycle of a dimming ratio control input signal and can be set to one of 16 levels with a minimum ratio of 1%.The LED dimming current is set by an external resistor to allow programming of LED current between 15mA and 30mA.

The dimming ratio of the MIC3263 is fixed to 16 log levels to better match the sensitivity of the human eye. Each of the dimming levels has hysteresis to avoid skipping between levels and allow for high noise immunity. The MIC3263 has a programmable PWM switching frequency from 400 KHz to 1.8 MHz to allow small inductor sizes. The 6V to 40V wide input voltage range of MIC3263 allows direct operation from 6V or high cell count Li-Ion batteries commonly found in notebook computers. The MIC3263 is available in a low-profile 24-pin 4mm x 4mm MLF® package and has a junction temperature range of C40℃ to -125℃.

MIC3263主要特性:

6V to 40V wide input voltage range

Drives 6 channels of up to 10 white LEDs

Programmable WLED current from 15mA to 30mA

Highly reliable operation with open and short LEDs

Accurate 16 dimming log levels sets the dimming ratio from 1% to 100%

Flicker-Free Dimming filters the jitter from the dimming control input signal and eliminates dimming flicker

Allows external dimming control

Accurate LED channel current matching ±3%

Accurate initial LED current setting ±2%

Programmable switching frequency from 400kHz to 1.8MHz

High efficiency up to 90%

Low (40µA) shutdown current over temperature

Over temperature protection

Programmable over-voltage protection

C40℃ to -125℃ junction temperature range

Available in 24-pin 4mm x 4mm MLF® package

MIC3263應用:

White LED driver for backlighting

Notebooks

LCD Panels and Monitors

Multimedia players

Navigation equipment

Gaming systems

Video poker

Slot machines

圖1.MIC3263功能方框圖