Low cost step-up-down 120ma DC-DC converter

Today's electronic projects often require multiple supply voltages. For example, 5V is commonly used to power microcontrollers (MCUs), while sensors and peripheral interface controllers typically operate at 3.3V. If your circuit includes both types of components, both voltages must be provided. Usually, one voltage is derived directly from the main power source (such as a battery or wall adapter), and the second voltage is generated from the first—using either a linear LDO regulator if it is lower, or a boost converter if it is higher.