LT3476 5V to 25V Buck-Boost Mode Driver for 2 Series 350mA LEDs
The LT3476 is a quad output DC/DC converter designed to operate as a constant-current source for driving high current LEDs. A ﬁxed frequency, current mode architecture results in stable operation over a wide range of supply and output voltages. A frequency adjust pin allows the user to program switching frequency between 200kHz and 2MHz to optimize efﬁciency and external component size. The LT3476 senses output current at the high side of the LED. High side current sensing is the most ﬂexible scheme for driving LEDs, allowing buck, boost or buckboost conﬁgurations. Each current monitor threshold is trimmed to within 2.5% at the full scale of 105mV. With an external sense resistor, the user programs the output current range of each channel. Each of the four regulators is independently operated by that channel’s PWM signal. This PWM feature allows precise adjustment of the color mixing or dimming ratio of the LED source. Dimming ratios up to 1000:1 can be achieved.