Maxim公司的MAX16834是电流模式高亮LED（HB LED）,可采用升压,升压－降压,SEPIC和高边降压拓扑．除了能驱动用于开关控制的N沟功率MOSFET,还能驱动Ｎ沟PWM调光开关，输入工作电压4.75V到28V，工作频率100kHz-1MHz,3000:1 PWM调光/模拟调光，主要用在单串LED LCD背光，汽车前后灯照明，投映系统RGB LED光源，DC/DC升压／升-降压转换器以及MR16,M111照明灯．本文介绍了MAX16834主要特性，方框图，各种应用电路以及采用全陶瓷电容的112W长串LED升压驱动器参考设计特性，电路图，PCB布局图．

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应用:

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

图1. MAX16834方框图

Boost LED Driver

图2. MAX16834升压-降压LED驱动电路(VLED+ < 28V)

图3. MAX16834带汽车负载突降保护的升压LED驱动电路

图4. MAX16834高边降压LED驱动电路

图5. MAX16834升压DC/DC转换器电路

图6. MAX16834升压-降压DC/DC转换器电路

采用全陶瓷电容的112W长串LED升压驱动器参考设计

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长串LED升压驱动器参考设计主要指标:

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

参考设计主要特性:

♦ 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


图6.112W长串LED升压驱动器参考设计外形图

图7.112W长串LED升压驱动器参考设计电路图
112W长串LED升压驱动器参考设计材料清单:



图8.112W长串LED升压驱动器参考设计PCB元件布局图
详情请见:
http://datasheets.maxim-ic.com/en/ds/MAX16834.pdf
和
http://pdfserv.maxim-ic.com/en/an/AN4669.pdf