Step-down converter 20V to 12V 0.5A

The MC34063A/E series is a monolithic control circuit which delivers the main functions for DCDC voltage converting. The device contains an internal temperature compensated reference, comparator, duty cycle controlled oscillator with an active current limit circuit, driver and high current output switch. Output voltage is adjustable through two external resistors with a 2% reference accuracy. Employing a minimum number of external components, the MC34063A/E device series is designed for step-down, step-up and voltageinverting applications. http://www.st.com/content/ccc/resource/technical/document/datasheet/03/f9/c4/3d/7f/eb/4c/5e/CD00001232.pdf/files/CD00001232.pdf/jcr:content/translations/en.CD00001232.pdf