Maxim MAX16838双路LED驱动方案

Maxim公司的MAX16838是集成了DC/DC开关升压转换器和两个150mA电流沉的双路LED驱动器,输入电压4.75V到40V,升压或SEPIC电源配置,200Hz的PWM调光比为5000:1,具有漏极开路故障指示输出以及LED开路/短路检测和保护,输出过压和超温保护,主要用在汽车显示器背光,汽车照明和LCD显示器背光.本文介绍了MAX16838主要特性, 方框图和升压-降压配置框图, SEPIC配置框图, 典型应用电路图以及MAX16838评估板主要特性,电路图,材料清单和PCB布局图.

The MAX16838 is a dual-channel LED driver that integrates both the DC-DC switching boost regulator and two 150mA current sinks. A current-mode switching DC-DC controller provides the necessary voltage to both strings of HB LEDs. The MAX16838 accepts a wide 4.75V to 40V input voltage range and directly withstands automotive load-dump events. For a 5V ±10% input voltage, connect VIN to VCC. The wide input range allows powering HB LEDs for small-to-medium-sized LCD displays in automotive and display backlight applications.

An internal current-mode switching DC-DC controller supports the boost or SEPIC topologies and operates in an adjustable frequency range between 200kHz and 2MHz. The current-mode control provides fast response and simplifies loop compensation. The MAX16838 also features an adaptive output-voltage adjustment scheme that minimizes the power dissipation in the LED current sink paths. The MAX16838 can be combined with the MAX15054 to achieve a buck-boost LED driver with two integrated current sinks.

The channel current is adjustable from 20mA to 150mA using an external resistor. The external resistor sets both channel currents to the same value. The device allows connecting both strings in parallel to achieve a maximum current of 300mA in a single channel. The MAX16838 also features pulsed dimming control with minimum pulse widths as low as 1µs, on both channels through a logic input (DIM).

The MAX16838 includes an output overvoltage protection, open LED, shorted LED detection, and overtemperature protection. The device operates over the -40°C to +125°C automotive temperature range. The MAX16838 is available in the 20-pin TSSOP and 4mm x 4mm, 20-pin TQFN packages.

MAX16838主要特性:

Integrated, 2-Channel, 20mA to 150mA Linear LED Current Sinks

Boost or SEPIC Power Topologies for Maximum Flexibility

Adaptive Voltage Optimization to Minimize Power Dissipation in Linear Current Sinks

4.75V to 40V or 5V ±10% Input Operating Voltage Range

5000:1 PWM Dimming at 200Hz

Open-Drain Fault Indicator Output

LED Open/Short Detection and Protection

Output Overvoltage and Overtemperature Protection

Programmable LED Current Foldback at Lower Input Voltages

200kHz to 2MHz Resistor Programmable Switching Frequency with External Synchronization

Current-Mode Control Switching Stage with Internal Slope Compensation
Enable Input

Thermally Enhanced, 20-Pin TQFN (4mm x 4mm) and 20-Pin TSSOP Packages

MAX16838应用:

Automotive Display Backlights

Automotive Lighting Applications

LCD Display Backlights

图1. MAX16838方框图

图2. MAX16838 SEPIC配置框图

图3. MAX16838升压-降压配置框图

图4. MAX16838典型应用电路图

The MAX16838 evaluation kit (EV kit) demonstrates the MAX16838 high-brightness LED (HB LED) driver, integrating a step-up DC-DC preregulator followed by two channels of linear current sinks. The step-up preregulator switches at 500kHz and operates as a current-modecontrolled regulator capable of providing up to 300mA for the linear circuits. Each channel is capable of operating up to 33V and provides up to 150mA. The channels are configurable for 100mA or 150mA HB LED output current.

The MAX16838 IC is available in a 20-pin TQFN package with an exposed pad for enhanced thermal power dissipation.

The MAX16838 EV kit operates from a DC supply voltage of 7V up to the HB LED string-forward voltage. The EV kit can withstand a 40V load-dump condition. The EV kit also demonstrates the MAX16838 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.

MAX16838评估板主要特性:

Input Voltage from 7V Up to HB LED Forward Voltage

Demonstrates Overvoltage Protection (35.6V)

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

Demonstrates UVLO (6.4V)

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

Demonstrates Adaptive Output-Voltage Optimization

Configurable LED Current Foldback (VIN < 6.5V)

Proven PCB and Thermal Design

Fully Assembled and Tested

图5.MAX16838评估板电路图
MAX16838评估板材料清单(BOM):



图6.MAX16838评估板元件布局图
详情请见:
http://datasheets.maxim-ic.com/en/ds/MAX16838.pdf
和
http://datasheets.maxim-ic.com/en/ds/MAX16838EVKIT.pdf