Maxim MAX16814四路高亮LED驱动方案

发布时间：2012-4-20 12:31 发布者：1770309616

Maxim 公司的MAX16814是集成了高压DC/DC控制器的四路高亮LED(HBLED)驱动器,输入电压4.75V-40V,能经受住汽车负载突变,可调输出电流从20mA到150mA,以驱动一到四串LED,开关频率200kHz到2MHz,自适应输出电压以最小化功耗,关断电流小于40uA,主要用在汽车显示屏LED背光,汽车RCL,DRL,前灯和雾灯,建筑物,工业和环境灯照明.本文介绍了MAX16814主要特性,功能框图,典型应用电路以及MAX16814 评估板主要特性,电路图,材料清单和PCB布局图.

The MAX16814 high-efficiency, high-brightness LED (HB LED) driver provides up to four integrated LED current-sink channels. An integrated current-mode switching DC-DC controller drives a DC-DC converter that pro-vides the necessary voltage to multiple strings of HB LEDs. The MAX16814 accepts a wide 4.75V to 40V input voltage range and withstands direct automotive load-dump events. The wide input range allows powering HB LEDs for small to medium-sized LCD displays in automotive and general lighting applications.

An internal current-mode switching DC-DC controller supports the boost, coupled-inductor boost-buck, or SEPIC topologies and operates in an adjustable fre-quency range between 200kHz and 2MHz. It can also be used for single-inductor boost-buck topology in conjunc-tion with the MAX15054 and an additional MOSFET. The current-mode control with programmable slope com-pensation provides fast response and simplifies loop compensation. The MAX16814 also features an adaptive output-voltage control scheme that minimizes the power dissipation in the LED current-sink paths.

The MAX16814 consists of four identical linear current source channels to drive four strings of HB LEDs. The channel current is adjustable from 20mA to 150mA with an accuracy of ±3% using an external resistor. The external resistor sets all 4-channel currents to the same value. The device allows connecting multiple channels in parallel to achieve higher current per LED string. The MAX16814 also features pulsed dimming control, on all four channels through a logic input (DIM). In addition,the MAX16814A_ _ and MAX16814U_ _ include a unique feature that allows a very short minimum pulse width as low as 1μs.

The MAX16814 includes an output overvoltage, open- LED detection and protection, programmable shorted LED detection and protection, and overtemperature pro-tection. The device operates over the -40NC to +125NC automotive temperature range. The MAX16814 is avail-able in 6.5mm x 4.4mm, 20-pin TSSOP and 4mm x 4mm, 20-pin TQFN packages.

MAX16814主要特性:

4-Channel Linear LED Current Sinks with Internal MOSFETs Full-Scale LED Current Adjustable from 20mA to 150mA Drives One to Four LED Strings Boost, SEPIC, or Coupled-Inductor Boost-Buck Current-Mode DC-DC Controller 200kHz to 2MHz Programmable Switching Frequency External Switching Frequency Synchronization
Adaptive Output-Voltage Optimization to Minimize Power Dissipation

4.75V to 40V Operating Input Voltage Range

Less than 40μA Shutdown Current

5000:1 PWM Dimming at 200Hz (MAX16814A _ _ and MAX16814U_ _ Only)

Open-Drain Fault Indicator Output

Open-LED and LED Short Detection and Protection

Overtemperature Protection

Thermally Enhanced, 20-Pin TQFN and TSSOP Packages

MAX16814应用:

Automotive Displays LED Backlights

Automotive RCL, DRL, Front Position, and Fog Lights

LCD TV and Desktop Display LED Backlights

Architectural, Industrial, and Ambient Lighting

图1.MAX16814 简化功能框图

图2.MAX16814典型应用电路图

图3.MAX16814 SEPIC配置图

图4.MAX16814电感耦合升压-降压配置图

MAX16814 评估板

The MAX16814 evaluation kit (EV kit) demonstrates the MAX16814 high-brightness LED (HB LED) driver, integrating a step-up DC-DC preregulator followed by 4 channels of linear current sinks. The step-up preregulator switches at 350kHz and operates as a current-modecontrolled regulator capable of providing up to 600mA for the linear circuits. Each of the 4 linear channels can operate up to 40V and provide up to 150mA per channel. The 4 channels are configurable for 100mA or 150mA HB LED output current. The IC is a 20-pin TSSOP package with an exposed pad for enhanced thermal power dissipation.

The EV kit operates from a DC supply voltage of 6.5V up to the HB LED string forward voltage. The EV kit can withstand a 40V load-dump condition. The EV kit also demonstrates the IC features such as adaptive voltage optimization, undervoltage lockout (UVLO), overvoltage protection (OVP), cycle-by-cycle current limit, thermal shutdown, and digital PWM dimming operation using a digital PWM input signal to control the brightness of the HB LEDs. The EV kit also demonstrates a reference IC design for automotive applications.

MAX16814 评估板主要特性:

Input Voltage from 6.5V Up to HB LED Forward Voltage

Demonstrates OVP (33V)

HB LED String Output Currents Configurable for 100mA or 150mA

Demonstrates UVLO (5V)

Demonstrates Open and Short LED Fault Protection and Detection

Demonstrates Cycle-by-Cycle Current Limit and Thermal-Shutdown Features

Demonstrates Adaptive Voltage Optimization

Proven PCB and Thermal Design

Fully Assembled and Tested