The project presented here is a powerful constant-frequency, pulse-width modulating (PWM), current-mode step-up DC-DC switching regulator efficiently producing 5V from input voltages between 3V to 5V. The project can be used in a portable device that works with a battery. The module produces a peak current of up to 1A and an output voltage of 5V DC.
3V to 5V DC Output Step-Up DC-DC Converter using MAX668 – [Link]