Test setup and performance summary

AN2833

22/32

11.4

3.3 V and 1.8 V output efficiency vs. load current

Figure 13 and 14 show the efficiency versus load current at 24 V of input voltage, in PWM

mode, skip mode and non-audible skip mode.

Figure 13.

3.3 V SMPS efficiency

Figure 14.

1.8 V SMPS efficiency

11.5

Power consumption analysis

To measure the device consumption in real working conditions, an external power supply of

+5 V is connected to EXT5V.

The two traces in the following figures show the differentiation in the two input currents.

Once the internal linear regulator is turned on, the device consumption increases.