Maxim 公司的MAX16834是電流模式大功率高亮度LED(HB led)驅動器,可組成升壓,升-降壓,SEPIC和高邊降壓拓撲.除了用開關PWM控制器驅動N溝功率MOSFET外,還能驅動N溝PWM調光開關. MAX16834輸入電壓從4.75V 到28V,3000:1 PWM調光/模擬調光,工作頻率從100kHz 到1MHz可編程,主要用在單串LED LCD背光,汽車前后照明,精密系統RGB LED光源,DC/DC升壓/升-降壓轉換器等.本文介紹MAX16834主要特性,方框圖,多種應用電路以及MAX16834評估板主要特性,電路圖,材料清單和PCB元件布局圖.

　　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 MAX16834s 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 DCDC 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

　　圖2.MAX16834升壓LED驅動器

　　圖3.MAX16834升壓-降壓LED驅動器(VLED+ < 28V)

　　圖4.MAX16834帶汽車電子負載突變保護的升壓LED驅動器

　　圖5.MAX16834高邊降壓LED驅動器

　　圖6.MAX16834升壓DC/DC轉換器

　　圖7.MAX16834升壓-降壓DC/DC轉換器

　　MAX16834評估板

　　The MAX16834 evaluation (EV kit) is a fully assembled and tested surface-mount PCB designed to evaluate the MAX16834 pulse-width modulated (PWM) HB LED driver controller in a step-up (boost) configuration and optional step-up/step-down (buck-boost) operation.

　　The MAX16834 EV kit operates from a DC supply voltage of 7V to 28V and requires up to 5A. The MAX16834 EV kit circuit is configured to deliver up to 1A of current into series LEDs with a maximum forward voltage of 28V.

　　The MAX16834 EV kit features two different types of dimming control using either an analog linear input voltage or digital PWM input signal to control the LED brightness. This EV kit has an undervoltage lockout (UVLO) feature that disables the EV kit and overvoltage protection that protects the circuit under no-load conditions. The EV kit also features a active-low FLT PCB pad to monitor for open or short-circuit LED conditions at the LED+ and LED- PCB pads. The MAX16834 EV kit is a fully assembled and tested surface-mount board.

　　MAX16834評估板主要特性:

　　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8.MAX16834評估板電路圖

　　MAX16834評估板材料清單(BOM):

　　圖9.MAX16834評估板元件布局圖