On the upper left of the schematic is the energy source noted as “solar cell”, the output of which is connected, via a small inductor, to the bq25504. The output voltage of the solar cell/energy source is limited to a maximum of 3 V and the peak input current is limited to 300 mA. The inductor is needed as the bq25504 is a boost device, which raises the input voltage to a higher voltage, and it employs pulse frequency modulation (PFM) for that process. The 2 resistors denoted as Roc1 and Roc2, connected to the node of the solar cell, inductor and Pin 2, are used to set the optimum sampling ratio of the dynamic MPPT, which is used in maximizing energy extraction.