8.4.4 Light Load Operation (PFM Option)

For PFM option, when the load current is lower than half of the peak-to-peak inductor current in CCM, the LMR23630-Q1 operates in DCM, also known as Diode Emulation Mode (DEM). In DCM, the LS switch is turned off when the inductor current drops to I_{L_ZC} (–40 mA typical). Both switching losses and conduction losses are reduced in DCM, compared to forced PWM operation at light load.

At even lighter current loads, PFM is activated to maintain high efficiency operation. When either the minimum HS switch ON-time (t_{ON_MIN} ) or the minimum peak inductor current I_{PEAK_MIN} (300 mA typical) is reached, the switching frequency decreases to maintain regulation. In PFM, switching frequency is decreased by the control loop when load current reduces to maintain output voltage regulation. Switching loss is further reduced in PFM operation due to less frequent switching actions. The external clock synchronizing is not be valid when LMR23630-Q1 enters into PFM mode.