Demonstration circuit 2220A is a 2A, bidirectional charger/regulator featuring the LTC3643, a bidirectional synchronous step-up charger and step-down converter. DC2220A implements backup by charging a storage capacitor up to approximately 40V in boost mode, when the input voltage is present. It discharges the storage capacitor in buck mode, providing a regulated load voltage 5V when the input is removed. Its wide voltage range, both in capacitor charger mode and in system backup mode, makes it well suited to a wide variety of applications. The ability of the LTC3643 to boost an input rail to a relatively high voltage of 40V, combined with the DC2220 option of adding external capacitor banks, makes this regulator an excellent choice for energy storage applications.