a5975d STMicroelectronics, a5975d Datasheet - Page 30

• Manufacturer Part Number: a5975d
• Description: Up To 3 A Step-down Switching Regulator For Automotive Applications
• Manufacturer: STMicroelectronics

Application information
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Figure 15. Power losses estimation (V
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
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
Figure 16. Power loss estimation (V
At V
the total power loss is now lower than 2.5 W ((
conduction loss).
As a consequence, the calculation of the internal power losses must be done for each
specific operating condition given by the final application.
IN
=12 V and V
plots the power losses for V
OUT
=5 V the device can deliver 3 A continuously (see
Figure 15
Doc ID 018760 Rev 1
the maximum power loss is for V
IN
IN
=12 V and main output rails.
= 12 V, f
IN
= 5 V, f
Δ
switching loss +
SW
SW
= 250 kHz)
= 250 kHz)
Δ
OUT
quiescent loss) <
=3.3 V, where the
Figure
17) because
A5975D
Δ