SLUSA75B July 2010 – January 2020 BQ24650
A solar panel has a unique point on the V-I or V-P curve, called the Maximum Power Point (MPP), at which the entire photovoltaic (PV) system operates with maximum efficiency and produces its maximum output power. The constant voltage algorithm is the simplest Maximum Power Point Tracking (MPPT) method. The BQ24650 automatically reduces charge current so the maximum power point is maintained for maximum efficiency.
If the solar panel or other input source cannot provide the total power of the system and BQ24650 charger, the input voltage drops. When the voltage sensed on the MPPSET pin drops below 1.2 V, the charger maintains the input voltage by reducing the charge current. If the MPPSET pin voltage is forced below 1.2 V, the BQ24650 stays in the input voltage regulation loop while the output current is zero. The STAT1 pin is LOW and STAT2 pin is HIGH.
The voltage at the MPPSET pin is regulated to 1.2 V, giving Equation 2 for the regulation voltage:
The MPPSET pin is also used as charge enable control. If the voltage on MPPSET is pulled down below 75 mV, charge is disabled. Charge resumes if the voltage on MPPSET goes back above 175 mV.