R5975D datasheet(30/47 Pages) STMICROELECTRONICS

tên linh kiện	R5975D

Giải thích chi tiết về linh kiện	Up to 3 A step-down switching regulator for aerospace applications

PDF	47 Pages

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Application information

R5975D

30/47

DocID026878 Rev 1

Figure 15 represents the estimation of power losses for different output voltages at VIN = 5 V

and TAMB = 40 C. The calculations are performed considering the RDS(on) of the power

element equal to 0.4 A.

Figure 15. Power losses estimation (VIN = 5 V, fSW = 250 kHz)

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

above, while the other traces are the total internal losses for different output voltages.

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 2.5 A. The device could deliver

a continuous output current up to 3 A to the load, however, the maximum power loss of 2.5

W is reached with an output current of 2.5 A, so the maximum output power is derated.

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

Figure 16. Power loss estimation (VIN = 12 V, fSW = 250 kHz)

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