a5975d STMicroelectronics, a5975d Datasheet - Page 27

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

A5975D
8.3
8.3.1
Figure 13. Layout example
Thermal considerations
Thermal resistance R
R
calculated as the parallel of many paths of heat conduction from the junction to the ambient.
For this device, the path through the exposed pad is the one conducting the largest amount
of heat. The static R
The junction temperature of the device is:
Equation 22
The dissipated power of the device is tied to three different sources:
●
Equation 23
where D is the duty cycle of the application. Note that the duty cycle is theoretically given by
the ratio between V
compensate for the losses in the overall application. For this reason, the switching losses
related to the R
THJ-A
Conduction losses due to the not insignificant R
is the equivalent static thermal resistance junction-to-ambient of the device; it can be
DS(on)
OUT
THJ-A
increase compared to an ideal case.
and V
measured on the application is about 40 °/W.
THJ-A
Doc ID 018760 Rev 1
IN
P
, but in practice it is substantially higher than this value to
ON
T
J
=
=
R
T
DS on
A
+
(
R
thJA
)
⋅
(
I
OUT
⋅
P
TOT
)
DS(on)
2
⋅
D
, which are equal to:
Application information
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