Low-voltage Input, 3v/3.3v/5v/ Adjustable Output, Step-up Dc-dc Converters

The MAX777L MAX778L MAX779L are pulse-skipping DC-DC converters that step up from low-voltage inputs (1V guaran- teed). They require only three external componentsan induc- tor (typically 22H) and two capacitors. The MAX777L delivers a 5V output, the MAX778L generates pin-selectable voltages of 3.0V or 3.3V, and the MAX779L output CAN be adjusted from 2.5V to 6V through an external resistive divider. The devices include an Active RectifierTM that eliminates the need for an external catch Diode and permits regulation even when the input is greater than the output. Also, unlike those in other Step-up converters, the MAX777L MAX778L MAX779Ls Active RectifierTM turns off in the shutdown mode, disconnect- ing the output from the source. This eliminates the current drain associated with conventional Step-up converters when off or in shutdown. High-frequency operation (up to 150kHz) allows the use of small, surface-mount inductors with values of 10H or less. Supply current is 190A under no load and only 20A in stand- by mode; supply voltage CAN range from 1V to 4.5V (1 to 3 cells). With a 2V input, the devices typically deliver 200mA at 5V, or 300mA at 3V. For fully specified devices designed for Step-up Step-down applications (where the input CAN be above or below the out- put), refer to the MAX877L/MAX878L/MAX879L data sheet. By Maxim Integrated Products