JAJSR90 September 2023 LMQ644A2-Q1
PRODMIX
Like auto mode operation, FPWM mode operation during light-load operation is selected using the SYNC/MODE pin.
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 the Electrical Characteristics for reverse current limit values.
In FPWM mode, frequency reduction is still available if output voltage is high enough to command minimum on-time, even while lightly loaded. This allows good behavior during faults which involves the output being pulled up.