SLVSHH4 Data sheet

SLVSHH4 July 2024 TPS546E25

ADVANCE INFORMATION

Package Options

Mechanical Data (Package|Pins)

RXX|37
- MPQF618C

Thermal pad, mechanical data (Package|Pins)

Orderable Information

slvshh4_oa

6.4.2 DCM Light Load Operation

When the operation mode is set to DCM, the device automatically reduces the switching frequency at light-load conditions to maintain high efficiency. This section describes the operation in detail.

As the output current decreases from heavy load condition, the inductor current also decreases until the rippled valley of the inductor current touches zero level. Zero level is the boundary between the continuous-conduction and discontinuous-conduction modes. The synchronous MOSFET turns off when this zero inductor current 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 the light-load operation I_OUT(LL) (for example: the threshold between continuous- and discontinuous-conduction mode) is calculated as shown in below equation.

Equation 11.

I_{O U T (L L)} = \frac{1}{2 \times L \times F s w} \times \frac{(V_{I N} - V_{O U T}) \times V_{O U T}}{V_{I N}}

Where

Fsw is the nominal continuous conduction switching frequency

The reduced switchng frequency at load currents less than I_OUT(LL) when in DCM are given by:

Equation 12.

F s w_{L L} = F s w \times \frac{I_{O U T}}{I_{O U T (L L)}}

The output voltage peak to peak ripple increases in load load operation, reaching upto 4× the continuous conduction ripple voltage at no load.

TI recommends using low ESR capacitors (such as ceramic capacitor) for skip-mode.