where the rippled valley touches zero level, which is the boundary between continuous conduction and

discontinuous conduction modes. The rectifying MOSFET is turned off when the zero inductor current is

detected. As the load current further decreases, the converter runs into discontinuous conduction mode. The on

time is kept almost the same as it was in continuous conduction mode so that it takes longer time to discharge

the output capacitor with smaller load current to the level of the reference voltage. This fact makes the switching

frequency lower, proportional to the load current, and keeps the light load efficiency high.

7.4.2 FCCM Mode Operation

The TPS563206 operates in forced CCM (FCCM) mode, which keeps the converter operating in continuous

current mode during light load conditions and allows the inductor current to become negative. During FCCM

mode, the switching frequency (FSW) is maintained at an almost constant level over the entire load range, which

is designed for applications requiring tight control of the switching frequency and output voltage ripple at the cost

of lower efficiency under light load.

TPS563203, TPS563206

SLUSEZ4 – MARCH 2023

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