LTC1157, Regulator Circuit Generates Both 3.3V and 5V Outputs from 3.3V or 5V to Run Computers and RS232

Circuit shows LT1111 is a buck-boost DC to DC converter. When input voltage is 5 it work as step-down converter to produces 3.3 output voltage, but when input voltage is 3.3 it work as step-up converter to produces 5 output voltage