This LED dimming circuit based on the LT3492 triple output DC DC converter introduced by Linear Technology.
LT3492 triple output DC DC converter is designed to operate as a constant-current source . The LT3492 works buck, boost or buckboost mode and is ideal for driving LEDs. The switching frequency of the LT3492 can be programmed between 330KHz and 2.1 MHz .
The external PWM input provides 3000:1 LED dimming on each channel. The LT3492 has three channels and each channel has a built-in gate driver to drive an external LED-disconnect P-channel MOSFET, allowing high dimming range. The output current range for each channel of the LT3492 is programmed with an external sense resistor.
The LT3492 use a CTRL pin to adjust the LED current either for analog dimming or overtemperature protection.
The main features of the LT3492 IC are : True Color PWM Dimming Delivers Up to 3000:1 Dimming Ratio , Built-In Gate Driver for PMOS LED Disconnect , Three Independent Driver Channels with 600mA , CTRL Pin Accurately Sets LED Current Sense Threshold Over a Range of 10mV to 100mV , Adjustable Frequency: 330kHz to 2.1MHz , Open LED Protection , Input Voltage Range from 3V to 30V .