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Maxim公司的MAX16834是電流模式高亮LED（HB LED）,可采用升壓,升壓－降壓,SEPIC和高邊降壓拓撲．除了能驅動用于開關控制的N溝功率MOSFET,還能驅動Ｎ溝PWM調光開關，輸入工作電壓4.75V到28V，工作頻率100kHz-1MHz,3000:1 PWM調光/模擬調光，主要用在單串LED LCD背光，汽車前后燈照明，投映系統RGB LED光源，DC/DC升壓／升-降壓轉換器以及MR16,M111照明燈．本文介紹了MAX16834主要特性，方框圖，各種應用電路以及采用全陶瓷電容的112W長串LED升壓驅動器參考設計特性，電路圖，PCB布局圖． The MAX16834 is a current-mode high-brightness LED (HB LED) driver for boost, boost-buck, SEPIC, and highside buck topologies. In addition to driving an n-channel power MOSFET switch controlled by the switching controller, it also drives an n-channel PWM dimming switch to achieve LED PWM dimming. The MAX16834 integrates all the building blocks necessary to implement a fixed-frequency HB LED driver with wide-range dimming control. The MAX16834 features constant-frequency peak current-mode control with programmable slope compensation to control the duty cycle of the PWM controller. A dimming driver designed to drive an external n-channel MOSFET in series with the LED string provides wide-range dimming control up to 20kHz. In addition to PWM dimming, the MAX16834 provides analog dimming using a DC input at REFI. The programmable switching frequency (100kHz to 1MHz) allows design optimization for efficiency and board space reduction. A single resistor from RT/SYNC to ground sets the switching frequency from 100kHz to 1MHz while an external clock signal at RT/SYNC disables the internal oscillator and allows the MAX16834 to synchronize to an external clock. The MAX16834’s integrated highside current-sense amplifier eliminates the need for a separate high-side LED current-sense amplifier in boost-buck applications. The MAX16834 operates over a wide supply range of 4.75V to 28V and includes a 3A sink/source gate driver for driving a power MOSFET in high-power LED driver applications. It can also operate at input voltages greater than 28V in boost configuration with an external voltage clamp. The MAX16834 is also suitable for DC/DC converter applications such as boost or boostbuck. Additional features include external enable/disable input, an on-chip oscillator, fault indicator output (FLT) for LED open/short or overtemperature conditions, and an overvoltage protection sense input (OVP+) for true overvoltage protection. The MAX16834 is available in a thermally enhanced 4mm x 4mm, 20-pin TQFN-EP package and in a thermally enhanced 20-pin TSSOP-EP package and is specified over the automotive -40℃ to +125℃ temperature range. MAX16834主要特性: _ Wide Input Operating Voltage Range (4.75V to 28V) _ Works for Input Voltage > 28V with External Voltage Clamp on VIN for Boost Converter _ 3000:1 PWM Dimming/Analog Dimming _ Integrated PWM Dimming MOSFET Driver _ Integrated High-Side Current-Sense Amplifier for LED Current Sense in Boost-Buck Converter _ 100kHz to 1MHz Programmable High-Frequency Operation _ External Clock Synchronization Input _ Programmable UVLO _ Internal 7V Low-Dropout Regulator _ Fault Output (FLT) for Overvoltage, Overcurrent, and Thermal Warning Faults _ Programmable True Differential Overvoltage Protection _ 20-Pin TQFN-EP and TSSOP-EP Packages MAX16834應用: Single-String LED LCD Backlighting Automotive Rear and Front Lighting Projection System RGB LED Light Sources Architectural and Decorative Lighting (MR16, M111) Spot and Ambient Lights DC-DC Boost/Boost-Buck Converters 
圖1. MAX16834方框圖
Boost LED Driver
圖2. MAX16834升壓-降壓LED驅動電路(VLED+ < 28V)
圖3. MAX16834帶汽車負載突降保護的升壓LED驅動電路
圖4. MAX16834高邊降壓LED驅動電路
圖5. MAX16834升壓DC/DC轉換器電路
圖6. MAX16834升壓-降壓DC/DC轉換器電路 采用全陶瓷電容的112W長串LED升壓驅動器參考設計 This reference design uses the MAX16834 to create a high-powered LED driver for a very long string(s) of LEDs. The LED current is adjustable with a potentiometer, and can be set as high as 1.5A into as many as 20 LEDs (75V total). For long life, ceramic capacitors are used for both input and output decoupling. This is a reference design for a 112.5W boost LED driver that uses the MAX16834 for long strings of LEDs. These long LED strings are commonly found in streetlights and parking garage lights. 112W長串LED升壓驅動器參考設計主要指標: Input voltage: 24VDC ±5% (at 1.49A) VLED configuration: Two parallel strings. Each string consists of 19 WLEDs and a 5Ω resistor for current balancing. Current is 750mA per sting for a total of 1.5A into 75V. Dimming: 50μs (min) on-pulse for up to a 200:1 dimming ratio with a 100Hz dimming frequency 參考設計主要特性: ♦ 7V to 28V Wide Supply Voltage Range ♦ Configured for Boost Operation ♦ Configurable for Buck-Boost Operation ♦ 1A Output Current ♦ Analog Linear Dimming Control ♦ PWM Dimming Control ♦ Open/Short-Circuit LED Fault Indicator (FLT) ♦ Demonstrates Output Overvoltage Protection ♦ Optional Load Dump Circuit ♦ Fully Assembled and Tested
圖6.112W長串LED升壓驅動器參考設計外形圖
圖7.112W長串LED升壓驅動器參考設計電路圖 112W長串LED升壓驅動器參考設計材料清單:
圖8.112W長串LED升壓驅動器參考設計PCB元件布局圖 詳情請見: 
MAX16834[1].pdf
(268.16 KB)
AN4669[1].pdf
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