In FPWM Mode, frequency is maintained while lightly loaded. To maintain frequency, a limited reverse current is allowed to flow through the inductor. Reverse current is limited by reverse current limit circuitry, see Section 7.5 for reverse current limit values.

In FPWM mode, Continuous Conduction (CCM) is possible even if I_OUT is less than half of I_ripple.

Figure 8-24 FPWM Mode Operation

Transitions between auto mode and FPWM mode can be commanded during operation if you are using the LM62435-Q1. These transitions are gradual, taking tens of clock cycles, allowing minimal disruption of output voltage during transitions. If the load is heavy enough to operate in CCM, since operation is identical in FPWM and Auto mode, no change in behavior is visible until the next time the circuit is lightly loaded.

For all devices, in FPWM mode, frequency reduction is still available if output voltage is high enough to command minimum on-time even while lightly loaded, allowing good behavior during faults which involve output being pulled up.