A5975AD datasheet(30/50 Pages) STMICROELECTRONICS

30 / 50 page

Application information

A5975AD

30/50

Doc ID 018761 Rev 1

Figure 15.

Power losses estimation (VIN = 5 V, fSW = 500 kHz)

The red trace represents the maximum power which can be taken away, as calculated

above, whilst the other traces are the total internal losses for different output voltage.

The embedded conduction losses are proportional to the duty cycle required for the

conversion. Assuming the input voltage constant, the switching losses are proportional to

the output current while the quiescent losses can be considered as constant.

As a consequence, in Figure 15, the maximum power loss is for VOUT=3.3 V, where the

system can manage a continuous output current up to 2.4 A. The device could deliver a

continuous output current up to 2.5 A to the load, however, the maximum power loss of 2.5

W is reached with an output current of 2.4 A, so the maximum output power is derated.

Figure 16 plots the power losses for VIN=12 V and the main output rails.

Figure 16.

Power losses estimation (VIN = 12 V, fSW = 500 kHz)

A5975AD Datasheet(PDF) 30 Page - STMicroelectronics