NS公司的LM3421/LM3423是多用途高压LED驱动,可以配置成降压,升压,降压-升压(反激)或SEPIC拓扑,输入电压从4.5V到高达75V,可调开关频率高达2MHz,具有快速(50kHz) PWM调光,关断电流小于1uA,可用在LED驱动器和多种恒流模式稳压器以及热电冷却驱动器.本文介绍了LM3421/LM3423的住要特性,方框图以及多种应用电路图,升压评估板主要特性和电路图和材料清单(BOM).

    LM3421/ LM3423:N-Channel Controllers for Constant Current LED Drivers

    The LM3421/LM3423 devices are versatile high voltage LED driver controllers. With the capability to be configured in a Buck, Boost, Buck-Boost (Flyback), or SEPIC topology, and an input operating voltage rating of 75V, these controllers are ideal for illuminating LEDs in a very diverse, large family of applications.

    Adjustable high-side current sense with a typical sense voltage of 100mV 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 LM3421/LM3423 include 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: “zero” current shutdown, precision reference, logic compatible DIM input suitable for fast PWM dimming, cycle-by-cycle current limit, and thermal

    shutdown.

    The LM3423 also includes an LED output status flag, a fault flag, a programmable fault timer, and a logic input to select the polarity of the dimming output driver.

    LM3421-3主要特性:

    ■VIN range from 4.5V to 75V

    ■2% Internal reference voltage (1.235V)

    ■Current sense voltage adjustable from 20mV

    ■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

    ■LED output status flag (LM3423 only)

    ■Fault timer pin (LM3423 only)

    ■TSSOP EP 16-lead package (LM3421)

    ■TSSOP EP 20-lead package (LM3423)

    LM3421-3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