As previously mentioned, the switching frequency for SMPS is set by the resistor. The frequency stays constant during all the transmitting period which forces the MOSFET working at a high frequency. That leads to the high-quiescent dissipation of the control chip. In this application note, a MOSFET combined with two additional resistors are used to change the switching frequency at the no-load period. The signal from GPIO can set the Fsw from 250 kHz to 100 kHz, which is only 46 mW at the maximum output voltage.

Figure 2-3 Switching Frequency Control by GPIO