The radio, MCU, and sensor all run on 1.5-3.6V, but the supercap and solar panel combination can go up to 5.5V. To regulate the power to lower voltage components a low-drop voltage regulator might ...
but they are functional under only a limited range of output current and/or load capacitance. Keep in mind that various applications can present a very wide range of load capacitance to the LDO ...