原标题：NS LM3429高压75V LED驱动调光解决方案

　　NS 公司的LM3429是多用途高压 LED驱动器控制器,可以配置成降压,升压,升/降压(Flyback)或SEPIC拓扑,输入和输出的工作电压额定值为75V,内部的PWM控制器可调开关频率高达2MHz.同时还集成了精密的基准电压,用于快速PWM调光的逻辑兼容DIM输入,逐个周期的限流和热关断.本文介绍了LM3429的主要特性, 典型应用电路以及LM2841/2 PWM DC/DC降压稳压器的主要特性,方框图和几种典型应用.同时还介绍了采用LM3429和LM2841/2的升/降压Nuventix参考设计电路图和评估板材料清单(BOM).

　　The LM3429 is a versatile high voltage LED driver controller.

　　With the capability to be configured in a Buck, Boost, Buck-Boost (Flyback), or SEPIC topology, and an input and output operating voltage rating of 75V, the LM3429 is ideal for illuminating LEDs in a very diverse, large family of applications.

　　Adjustable high-side current sense with a typical sense voltage of 100 mV allows for tight regulation of the LED current with the highest efficiency possible. Output LED current regulation is based on peak current-mode control with predictive Off-Time Control. This method of control eases the design of loop compensation while providing inherent input voltage feed-forward compensation.

　　The LM3429 includes a high-voltage startup regulator that operates over a wide input range of 4.5V to 75V. The internal PWM controller is designed for adjustable switching frequencies of up to 2.0MHz, thus enabling compact solutions. Additional features include: precision reference, logic compatible DIM input suitable for fast PWM dimming,cycle-by-cycle current limit, and thermal shutdown.

　　The LM3429 comes in a low profile, thermally efficient TSSOP EP 14-lead package.

　　LM3429主要特性:

　　■ VIN range from 4.5V to 75V

　　■ 2% Internal reference voltage (1.235V)

　　■ Current sense voltage adjustable from 20 mV

　　■ High-side current sensing

　　■ 2Ω MOSFET gate driver

　　■ Dimming MOSFET gate driver

　　■ Input under-voltage protection

　　■ Over-voltage protection

　　■ Low shutdown current, IQ < 1μA

　　■ Fast (50kHz) PWM dimming

　　■ Cycle-by-cycle current limit

　　■ Programmable switching frequency

　　■ TSSOP EP 14-lead package

　　LM3429应用:

　　■ LED Drivers

　　■ Constant-Current Buck-Boost Regulator

　　■ Constant-Current Boost Regulator

　　■ Constant-Current Flyback Regulator

　　■ Constant-Current SEPIC Regulator

　　■ Thermo-Electric Cooler (Peltier) Driver

图1.LM3429典型应用电路

　　The LM2841 and LM2842 are PWM DC/DC buck (step-down) regulators. With a wide input range from 4.5V-42V, they are suitable for a wide range of applications such as power conditioning from unregulated sources. They feature a low RDSON (0.9Ω typical) internal switch for maximum efficiency (85% typical). Operating frequency is fixed at 550 kHz (X version) and 1.25 MHz (Y version) allowing the use of small external components while still being able to have low output voltage ripple. Soft-start can be implemented using the shutdown pin with an external RC circuit allowing the user to tailor the soft-start time to a specific application.

　　The LM2842 is optimized for up to 600 mA load currents while the LM2841 is optimized for up to 300 mA load current. Both have a 0.765V nominal feedback voltage.

　　Additional features include: thermal shutdown, VIN under-voltage lockout, and gate drive under-voltage lockout. The LM2841 and LM2842 are available in a low profile TSOT-6L package.

　　LM2841/2主要特性:

　　■ Input voltage range of 4.5V to 42V

　　■ Output current options of 300 mA and 600 mA

　　■ Feedback pin voltage of 0.765V

　　■ 550 kHz (X) or 1.25 Mhz (Y) switching frequency

　　■ Low shutdown IQ, 16 μA typical

　　■ Short circuit protected

　　■ Internally compensated

　　■ Soft-start circuitry

　　■ Small overall solution size (TSOT-6L package)

　　LM2841/2应用:

　　■ Battery powered equipment

　　■ Industrial distributed power applications

　　■ Portable media players

　　■ Portable hand held instruments

图2.LM2841/2方框图

图3.LM2841/2应用电路,3.3V输出

图4.LM2841/2应用电路,5V输出

图5.LM2841/2应用电路,12V输出

图6.LM2841/2应用电路,15V输出

图7.LM2841/2应用电路,0.8V输出

　　LM3429升/降压Nuventix参考设计和评估板

　　LM3429 BUCK-BOOST Nuventix Reference design and Evaluation PCB

　　The demonstration board includes a LM3429 device that converts 9VDC to 36VDC input to a 700mA constant current output designed to operate a load of three to four series LEDs. This is a 4-layer board having input voltage and ground as the two internal planes. The design has been made assuming there are analog dimming requirements.

　　A bill of materials below describes the parts used on this demonstration board. A schematic and layout have also been included below along with measured performance characteristics of this demo board.

　　图8.采用LM3429和LM2842的MR16 LED终端应用解决方案

　　MR16 LED retrofit bulb complete with a LED and a lens for a total end application solution

图.高边检测电路

　　LM3429 LED 驱动器,调光评估板材料清单(BOM):

　　LM3429 Buck-Boost: High Side Current Sense (2kohm Potentiometer Dimming)