Maxim MAX17129低成本6串白光LED驱动方案
发布时间：2011-11-3 13:18
发布者：1640190015
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Maxim公司的MAX17129/MAX17149是高效率白光LED（WLED）驱动器，适合中小型LCD屏采用LED作为光源。工作电压3-26V，可驱动六串多个LED串联的LED串，串间电流匹配度在±2%内，支持PWM和混合调光模式，调光比100：1，PWM调光模式的调光频率100Hz到25kHz，LED电流从10mA到45mA可调，具有LED开路和短路保护以及输出过压保护，主要用用在笔记本电脑和平板电脑，显示器，汽车系统和手持终端。本文介绍了MAX17129/MAX17149主要特性，方框图，典型工作电路图以及MAX17129评估板主要特性，电路图，材料清单和PCB布局图。 MAX17129/17149：Low-Cost, 6-String WLED Drivers with Quick-PWM Step-Up Converters The MAX17129/MAX17149 are high-efficiency drivers for white LEDs. They are designed for small- to mediumsized LCDs that employ an array of LEDs as the light source. An internal switch step-up controller with Quick- PWMK drives the LED array, which can be configured for up to 6 strings in parallel and either 11 LEDs (MAX17129) or 6 LEDs in series (MAX17149) per string. Each string is terminated with a ballast that achieves Q2% currentregulation accuracy, ensuring even LED brightness and provides an adjustable 10mA to 45mA full-scale LED current. The devices have a wide input voltage range of 6V to 26V. The MAX17129 integrates an LDO to simplify applications that have a single high-voltage supply. The devices also feature a low-input-voltage mode for applications that have a 3V to 5.5V supply voltage. The devices support both PWM and hybrid dimming mode. In PWM dimming mode, the external PWM signal directly controls the brightness of LEDs. The dimming frequency ranges from 100Hz to 25kHz with 400ns minimum on-time. In hybrid dimming mode, the LED current amplitude can be adjusted to 25% of full-scale LED current to improve system efficiency when brightness is low. The devices have multiple features to protect the controller from fault conditions. Separate voltage-feedback loops limit the output voltage to safe operation. The open and short-LED detection shuts down the faulty string while keeping other strings operating normally. The devices feature cycle-by-cycle current limit on the internal switch to provide consistent operation and softstart capability. If the devices are in current-limit condition, the step-up converter is latched off after an internal timer expires. A thermal-shutdown circuit provides another level of protection and prevents ICs from damage. The ICs’ step-up controller features an internal 0.25I (typ), 48V (max) power MOSFET with lossless current sense and accurate cycle-by-cycle current limit. The Quick-PWM control architecture provides fast load-transient response without requiring an external loop compensation component, simplifies the external circuitry, and saves board area. The Quick-PWM control scheme has constant off-time and adjustable pseudo-fixed frequency, which enables a wide variety of applications that can trade off component size for operating frequency. Low feedback voltage at each LED string (275mV typ at 20mA LED current) helps reduce power loss and improve efficiency. The ICs are available in a 16-pin, thin QFN package with 0.5mm lead spacing. The package is 3mm x 3mm with a maximum thickness of 0.8mm for ultra-thin LCD panel design. MAX17129/MAX17149主要特性： 3V to 26V Input Supply Voltage Up to Six Parallel Strings of Multiple Series-Connected LEDs Step-Up Regulator with Quick-PWM Control Scheme Two-Level Selectable Switching Frequency 0.25I Internal HV Power MOSFET (48V max) Low String Feedback Voltage: 275mV at 20mA LED Current Full-Scale LED Current Adjustable from 10mA to 45mA ±2% Current Regulation Accuracy Between Strings Support PWM and Hybrid Dimming Mode 100:1 Dimming Ratio 100Hz to 25kHz Dimming Frequency for PWM Dimming Mode Open and Short LED Protection Output Overvoltage Protection Small 16-Pin, 3mm x 3mm Thin QFN Package MAX17129/MAX17149应用： Notebook, Subnotebook, and Tablet Computer Displays Automotive Systems Handy Terminals 
图1。MAX17129/MAX17149方框图 
图2。MAX17129/MAX17149典型工作电路图 MAX17129评估板 The MAX17129 evaluation kit (EV kit) provides a proven design to evaluate the MAX17129 high-efficiency driver for white light-emitting diodes (WLEDs). The EV kit utilizes a step-up DC-DC converter to generate the voltage required to drive up to six strings of 10 surface-mount WLEDs. The EV kit uses a 3V to 26V input supply and can be configured to provide an adjustable 10mA to 45mA full-scale LED current. Installed on the EV kit is the MAX17129ETE+. Contact the factory for free samples of the pin-compatible MAX17149ETE+. MAX17129评估板主要特性： 3V to 26V Input Range Drives Six Strings of 10 WLEDs Full-Scale LED Current Adjustable from 10mA to 45mA Adjustable Switching Frequency of 500kHz or 1MHz Proven PCB Layout Fully Assembled and Tested 
图3。MAX17129评估板电路图 MAX17129评估板材料清单（BOM）： 
图4。MAX17129评估板PCB布局图 详情请见： 
MAX17129-MAX17149[1].pdf
(1.92 MB)
MAX17129EVKIT[1].pdf
(993.77 KB)
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