LM3423 应用LED升压驱动方案
国半LM3423芯片适用于高达75V的输入电压,可升降压应用，
可出高达20个1W串接 LED，应用太阳能路灯等，效率90以上；
       VIN range from 4.5V to 75V
 2% 1.25V Internal reference voltage
 Current sense voltage adjustable from 50mV to 1.25V
 High side current sensing
 750mA peak MOSFET gate driver
 Dimming MOSFET gate driver
 Input under-voltage protection
 Output over-voltage protection
 LED ready flag
 Low shutdown current, Iq < 1?A
 Fast (50 KHz) PWM dimming input 
 Cycle-by-cycle current limit
 Programmable running frequency
 Fault timer pin
 TSSOP-20 package
        Applications
 LED Drivers
 Constant Current Buck-Boost Regulator
 Constant Current Boost Regulator
 Constant Current Flyback Regulator
 Constant Current SEPIC Converter
 Thermo-Electric Cooler (Peltier) Driver