The output current of the LTC3625 and LTC3625-1’s buck converter is user-programmable via the PROG pin, and the input current of the boost converter is set at 2A typically. The resulting maximum charge current is 1A continuous with two inductors, and 500mA with a single inductor configuration. Each capacitor is protected against overvoltage by internal voltage clamps of 2.4V or 2.65V selectable for LTC3625 and 2.0V or 2.25V selectable for the LTC3625-1. The LTC3625 and LTC3625-1’s automatic cell balancing feature maintains approximately equal voltages across both cells, eliminating the need for balancing resistors while protecting each supercapacitor from overvoltage damage. The LTC3625 and LTC3625-1 operate with a very low 23µA quiescent current when the output voltage is in regulation. When the input supply is removed or the EN pin is low, the LTC3625 automatically enters a low current state, drawing less than 1µA from the supercapacitors. The basic charging circuit requires only three external components (one inductor, one bypass capacitor at V_IN and one programming resistor) and is highly compact, offered in a tiny 12mm² package footprint. Additional protection features include over-temperature protection for momentary overload conditions, over-current limiting, and reverse-current protection in which the device will continue to regulate at its programmed current even into a grounded output.