LT1618 DC/DC Converter

ADI's LT1618 step-up DC/DC converter combines a traditional voltage feedback loop and a unique current feedback loop to operate as a constant-current, constant-voltage source. This fixed frequency, current mode switcher operates from a wide input voltage range of 1.6 V to 18 V, and the high switching frequency of 1.4 MHz permits the use of tiny, low-profile inductors and capacitors. The current sense voltage is set at 50 mV and can be adjusted using the I_ADJ pin.

Available in the 10-pin (3 mm x 3 mm) exposed pad DFN and 10-pin MSOP packages, the LT1618 provides a complete solution for constant-current applications.

Demonstration circuit DC780B is a constant-current, constant-voltage 1.4 MHz step-up DC/DC converter featuring the LT1618. DC780B demonstrates a general-purpose boost converter with a 12 V, 250 mA output from a 3.3 V to 4.2 V source. This demo board can also be used as an LED driver, where a Luxeon LED (not installed) is driven with a regulated current of 500 mA (default current) at a forward voltage of 3.5 V. By changing the value or R4 to 2.2 M the LED current can be regulated at 250 mA. The LT1618 can be used for wider input voltages, but output voltage level and component selection restrict this demo circuit to Lithium-ion battery input levels.