Demo circuit 1647 is a current-mode PWM step-down DC/DC regulator with an internal power switch featuring the LT3686A. The LT3686A differs from the LT3686 in that it offers higher transient voltage protection and a SYNC pin. The demo circuit is designed for 3.3V/1.2A output from a 5V to 37V input with transients up to 55V. Its high 2.5MHz maximum frequency allows the use of tiny inductors and capacitors. Operating frequency above the AM band avoids interfering with radio reception, making the LT3686 particularly suitable for automotive applications. The LT3686A offers external synchronization capability, whereas the LT3686 does not.