Datasheet
Temperature Considerations
3-6
3.2 Temperature Considerations
To protect the device and assure the specifications, the maximum junction
temperature should not exceed 125°C. This restriction limits the power dis-
sipation the regulator can handle in any given application. To ensure the junc-
tion temperature is within acceptable limits, calculate the maximum allowable
dissipation, P
D(max)
, and the actual dissipation, P
D
, which must be less than
or equal to P
D(max)
. The maximum power dissipation limit is determined using
the following equation:
P
D
(
max
)
T
J
,
max
T
A
R
JA
Where
T
J,max
is the maximum allowed junction temperature [°C], i.e., 125°C for
the TPS76xxx/TPS77xxx families
R
θJA
is the thermal resistance junction-to-ambient for the package, i.e.,
285°C/W for the 5-terminal SOT23
T
A
is the ambient temperature
The regulator dissipation is calculated using:
P
D
V
IN
V
OUT
I
OUT
The maximum output current at a given temperature can be calculated as:
I
out
,
max
[
mA
]
125°
C T
A
V
in
V
out
285°
C W
1000
mA
Figure 3–3 shows the test results on a TPS76933 device. Also displayed are
the calculated results.