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, the MCP16367 delivers a packet of current pulses, followed by sleep periods where the output is maintained by the output capacitor. When in Sleep mode, the MCP16367 consumes around 18 µA from the input. As the output load decreases,both the frequency and duration of the current pulse packets are reduced, resulting in longer sleep periods. By maximizing the sleep time, the converter’s no-load input current approaches the 18 µA value. To further 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.