SLVSGP3A May 2023 – February 2024 TPS54KB20
PRODUCTION DATA
If the MSEL resistor value used selects Skip-mode, the device automatically reduces the switching frequency at light-load conditions to maintain high efficiency. Multifunction Select (MSEL) Pin describes the selection in detail.
As the output current decreases from heavy load condition, the inductor current also decreases until the valley of the inductor ripple current touches the zero-crossing threshold (Low-side MOSFET Zero-Crossing). The zero-crossing threshold sets the boundary between the continuous-conduction and discontinuous-conduction modes. The synchronous MOSFET turns off when this zero-crossing threshold is detected. As the load current decreases further, the converter runs into discontinuous-conduction mode (DCM). The on-time is maintained to a level approximately the same as during continuous-conduction mode operation so that discharging the output capacitor with a smaller load current to the level of the reference voltage requires more time. The transition point to light-load operation IOUT(LL) (for example: the boundary between continuous- and discontinuous-conduction mode) is calculated as shown in Equation 7.
For low output ripple, TI recommends using only ceramic output capacitors for designs that operate in skip-mode.