When MPPT is enabled, the LTC4013 periodically measures the open-circuit input voltage. About once every 10.2s the LTC4013 pauses charging, samples the input voltage as measured through a resistor divider at the FBOC pin, and reproduces this value internally with a digital-to-analog converter (DAC). When charging resumes, the DAC voltage, VDAC, is compared against the MPPT pin voltage that is programmed with a resistor divider. If the MPPT voltage falls below VDAC, charge current is reduced to regulate the input voltage at that level. This regulation loop maintains the input voltage at or above a user defined level that corresponds to the peak power available from the applied source. Regular input sampling is useful, for instance, to provide first order temperature compensation of a solar panel.