NS 公司的LM3463是四路高壓LED驅動器，LM3464輸入電壓為12V-80V，LM3464A輸入電壓為12V-95V，四路輸出可單獨電流穩壓，通路間的精度高，數字PWM/模擬調光控制接口，動態靜空控制最大化效率，主要用于街燈照明和固態照明解決方案。本文介紹了LM3464/64A 主要特性，方框圖，典型應用電路圖，LM3464 4路LED驅動器評估板主要特性，電路圖，材料清單和PCB元件布局圖。
LED Driver with Dynamic Headroom Control and Thermal Control Interfaces
The LM3464/64A is a 4-channel high voltage current regulator that provides a simple solution for LED lighting applications. The LM3464/64A provides four individual current
regulator channels and works in conjunction with external Nchannel MOSFETs and sense resistors to give accurate driving current for every LED string. Additionally, the Dynamic Headroom Control (DHC) output can be interfaced to the external power supply to adjust the LED supply voltage to the lowest level that is adequate to maintain all the string currents in regulation, yielding the optimal overall efficiency.
Digital PWM or analog voltage signals can be used to control the duty cycle of the all the channels. When analog control is used, the dimming frequency can be programmed via an external capacitor. A minimum duty cycle control is provided in the conditions that the analog dimming is configured as thermal feedback.
Protection features include VIN under-voltage lock-out, LED open/short circuit and over-temperature fault signaling to the system controller.
LM3464/64A 主要特性：
■ Wide input voltage range
12V-80V (LM3464)
12V–95V (LM3464A)
■ Dynamic Headroom Control ensures maximum efficiency
■ 4 output channels with individual current regulation
■ High channel to channel accuracy
■ Digital PWM/Analog dimming control interface
■ Resistor programmable dimming frequency & minimum duty cycle (analog dimming mode)
■ Direct interface to thermal sensor
■ Fault detection
■ Over temperature protection
■ Thermal shutdown
■ Under voltage lockout
■ Thermal enhanced eTSSOP-28 package
LM3464/64A應用：
■ Streetlights
■ Solid State Lighting Solutions
圖1。LM3464/64A方框圖
圖2。LM3464/64A典型應用電路圖
圖3。LM3464/64A和反激AC/DC轉換器的典型應用電路圖
圖4。LM3464/64A帶熱折返控制的級聯應用電路圖
LM3464 4路LED驅動器評估板
The LM3464 is a linear LED driver with Dynamic Headroom Control (DHC) technology designed to drive four serial high power / high brightness LED strings. Four individual linear current regulators with low-side N-channel MOSFETs realize regulations of LED currents. The DHC optimizes system efficiency automatically while maintaining stable and accurate LED currents. The LM3464 includes a voltage regulator for powering the internal circuits that operates over wide input range of 12V to 80V, eases the design of driver stage for different source voltage. The Thermal foldback feature is designed to prolong the lifetime of the LEDs by reducing the average LED current for applications with high ambient temperature.
The LM3464 features a fault handling circuit that avoids system failure due to accidentally short or open circuit of LED strings. Two or more LM3464 can be cascaded to expand the number of output channels, enabling flexible system architectural design.
This evaluation board demonstrates the system efficiency and LED current regulation accuracy of the LM3464 LED driver typical application circuit as a 50W LED lighting system.
The schematic, bill of material and PCB layout for the evaluation board are provided in this document. The evaluation board can adapt to different types of primary power supplies
with changes of value of a few components only.
LM3464 4路LED驅動器評估板主要特性：
• Vin range 12V to 80V
• 48V LED turn ON voltage
• 350mA LED current per channel
• 2kHz thermal foldback dimming frequency
As the LED turn-on voltage of the LM3464 evaluation board is designed to 48V, it is recommended to set the supply voltage to the evaluation board no more than 60V to avoid high power dissipation on the MOSFETs of the low-side current regulators upon system startup. For driving different number of LEDs, the startup voltage will need to be adjusted by changing the value of the resistors RFB1 and RFB2.
LM3464 4路LED驅動器評估板主要特性：
• Dynamic Headroom Control (DHC)
• Thermal foldback control
• High speed PWM dimming
• Minimum brightness limit for thermal foldback control
• Cascade operation for output channel expansion
• Vin Under-Voltage-Lockout
• Fault protection and indication
• Programmable startup voltage
• Thermal Shutdown
圖5。LM3464 4路LED驅動器評估板外形圖
圖6。LM3464 4路LED驅動器評估板電路圖
LM3464 4路LED驅動器評估板材料清單：
圖7。LM3464 4路LED驅動器評估板級聯擴展輸出通路
圖8。LM3464 4路LED驅動器評估板PCB元件布局圖
詳情請見：
http://www.national.com/ds/LM/LM3464.pdf
和
http://www.national.com/an/AN/AN-2071.pdf
