Multiple LTC3625's can be stacked in series to store significantly more energy and extend hold up time in ride through or last gasp applications. In this circuit, the three outputs of the LT1737 flyback converter drive three LTC3625's, each of which charges a pair of 100F capacitors. In the event of an interruption to the main power supply, the supercapacitors can power the system for up to several seconds. The LTC3625/LTC3625-1 are programmable supercapacitor chargers designed to charge two supercapacitors in series to a fixed output voltage (4.8V/5.3V or 4V/4.5V selectable) from a 2.7V to 5.5V input supply. Automatic cell balancing prevents overvoltage damage to either supercapacitor while maximizing charge rate. No balancing resistors are required.