Linear Technology Corporation has introduced the LT3475, 36 V, up to 2 MHz step-down dc/dc converter designed to operate as a two-channel, constant-current LED driver. Each channel has an internal sense resistor and dimming control, which suit the device for driving LEDs that require up to 1.5 A of current. One channel switches 180° out-of-phase with the other for reduced input ripple.
High output current accuracy is maintained independently for each channel over a 50 mA to 1.5 A range, according to the company. “True Color PWM” circuitry allows a dimming range of 3000:1 without the color shift typically associated with LED current dimming. With a 4 V to 36 V input voltage range (transients up to 40 V), the LT3475 regulates a wide range of power sources including automotive power systems.
Its switching frequency can be set with a single resistor from 200 kHz to 2 MHz, enabling the use of tiny inductors and ceramic capacitors. It uses a high side sense that enables a grounded LED cathode connection, thus eliminating the need for a LED return wire in most applications. It also integrates a boost diode for each channel, further reducing the solution footprint and cost. Other features include open LED and short circuit protection. The LT3475 is available in a thermally enhanced TSSOP-20.