NS 公司的LM3409/09HV是用于降壓電流調整的P溝MOSFET（ PFET）控制器，LM3409/LM3409Q輸入電壓從6V到42V，LM3409HV/LM3409QHV輸入電壓從6V到75V。PWM調光范圍10000:1，模擬調光范圍250:1，支持所有的陶瓷電容輸出和無電容輸出能驅動正向電流達5A的大功率LED，主要用在LED驅動器" title="LED驅動器">LED驅動器，恒流源，汽車照明，通用照明和工業照明。本文介紹了LM3409/09HV主要特性，方框圖，多種應用電路和相應的材料清單，以及LM3409HV評估板電路圖和評估板材料清單。
PFET Buck Controller for High Power LED Drivers
The LM3409/09HV are P-channel MosFET (PFET) controllers for step-down (buck) current regulators. They offer wide input voltage range, high-side differential current sense
with low adjustable threshold voltage, fast output enable/disable function and a thermally enhanced eMSOP-10 package.
These features combine to make the LM3409/09HV ideal for use as constant current sources for driving LEDs where forward currents up to 5A are easily achievable.
The LM3409/09Q/09HV/09QHV uses Constant Off-Time (COFT) control to regulate an accurate constant current without the need for external control loop compensation. Analog and PWM dimming are easy to implement and result in a highly linear dimming range with excellent achievable contrast ratios.
Programmable UVLO, low-power shutdown, and thermal shutdown complete the feature set.
LM3409/09HV主要特性：
■ LM3409Q/LM3409QHV is an Automotive Grade product that is AEC-Q100 grade 1 qualified
■ 2Ω, 1A Peak MosFET Gate Drive
■ VIN Range: 6V to 42V (LM3409/LM3409Q)
■ VIN Range: 6V to 75V (LM3409HV/LM3409QHV)
■ Differential, High-side Current Sense
■ Cycle-by-Cycle Current Limit
■ No Control Loop Compensation Required
■ 10,000:1 PWM Dimming Range
■ 250:1 Analog Dimming Range
■ Supports All-Ceramic Output Capacitors and Capacitorless Outputs
■ Low Power Shutdown
■ Thermal Shutdown Protection
■ Thermally Enhanced eMSOP-10 Package
LM3409/09HV應用：
■ LED Driver
■ Constant Current Source
■ Automotive Lighting
■ General Illumination
■ Industrial Lighting
圖1。LM3409/09HV方框圖
圖2。LM3409/09HV典型應用電路圖
圖3。LM3409/09HV PWM調光10個LED驅動電路圖
圖3材料清單：
圖4。LM3409/09HV 模擬調光4個LED驅動電路圖
圖4材料清單：
圖5。LM3409/09HV 外接并聯FET PWM調光10個LED驅動電路圖
圖5材料清單：
圖6。LM3409/09HV 單個電位計模擬調光6個LED驅動電路圖
圖6材料清單：
圖7。LM3409/09HV 75度C熱折返16個LED驅動電路圖
圖7材料清單：
圖8。LM3409/09HV 大電流4個LED驅動電路圖
圖8材料清單：
LM3409HV評估板
This evaluation board showcases the LM3409HV PFET controller for a buck current regulator. It is designed to drive 12 LEDs (VO = 42V) at a maximum average LED current (ILED = 1.5A) from a DC input voltage (VIN = 48V). The switching frequency (fSW = 400 kHz) is targeted for the nominal operating point, however fSW varies across the entire operating range.
The circuit can accept an input voltage of 6V-75V. However, if the input voltage drops below the regulated LED string voltage, the converter goes into dropout and VO = VIN ideally. The PCB is made using 4 layers of 2 oz. copper with FR4 dieletric. The evaluation board showcases all features of the LM3409HV including analog dimming using the IADJ pin and internal PWM dimming using the EN pin. High frequency external parallel FET shunt PWM dimming can also be evaluated.
The board has a header (J1) with a removable jumper, which is used to select the PWM dimming method. The evaluation board has a right angle connector (J2) which can mate with an external LED load board allowing for the LEDs to be mounted close to the driver. This reduces potential ringing when there is no output capacitor. Alternatively, the LED+ and LED- turrets can be used to connect the LED load.
This board can be easily modified to demonstrate other operating points as shown in the Alternate Designs section. The LM3409/09HV datasheet Design Procedure can be used to design for any set of specifications.
Since the board contains a buck regulator designed for 48V input, the efficiency is very high at input voltages near or less than 48V. The switching frequency increases as input voltage increases, yielding lower efficiency at higher input voltages.
Note that increasing the off-time resistor (R6) will increase the efficiency at high input voltage.
圖9。LM3409HV評估板外形圖
圖10。LM3409HV評估板電路圖
LM3409HV評估板材料清單：
詳情請見：
http://www.national.com/ds/LM/LM3409.pdf
和
http://www.national.com/an/AN/AN-1953.pdf
