8.8 Light Load Efficiency Guidelines

To increase efficiency at light load conditions, the MCP16367 operates in PFM to keep the output voltage regulated while minimizing the input current consumption. In this mode of operation, the MCP16367 delivers a packet of current pulses that is followed by sleep periods where the output is maintained by the output capacitor. When in the Sleep mode, the MCP16367 consumes around 18 µA from the input. As the output load decreases, the frequency and length of the packet of pulses decrease such that the sleep period extends over most of the time. By maximizing the sleep time, the converter operating no load input current gets closer to the 18 µA value. To optimize the performance at light loads, the current flowing through the feedback resistors and the reverse current through the freewheeling diode must be minimized, as they are seen as load currents. It is recommended that the feedback resistors be in the order of tens of kΩ in range and that the freewheeling diode reverse current be less than 1 µA at room temperature.