Texas Instruments TPS72728DSEEVM-406 Evaluation Module TPS72728DSEEVM-406 TPS72728DSEEVM-406 데이터 시트
제품 코드
TPS72728DSEEVM-406
4
Thermal Guidelines
4.1
Thermal Considerations
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Thermal Guidelines
This chapter provides guidelines for the thermal management of the TPS727xxDSEEVM-406 board.
Thermal management is a key component of design of any power converter and is especially important
when the power dissipation in the LDO is high. To better help you design the TPS727xx family into your
application, the following formula should be used to approximate the maximum power dissipation at a
particular ambient temperature:
when the power dissipation in the LDO is high. To better help you design the TPS727xx family into your
application, the following formula should be used to approximate the maximum power dissipation at a
particular ambient temperature:
T
J
= T
A
+ P
d
× θ
JA
(1)
Where
T
J
is the junction temperature,
T
A
is the ambient temperature,
P
d
is the power dissipation in the IC and
θ
JA
is the thermal resistance from junction to ambient.
All temperatures are in degrees Celsius.
The measured thermal resistance from junction to ambient for the TPS727xxEVM has a typically value of
130
130
°
C/W. The recommended maximum operating junction temperature specified in the datasheet for the
TPS727xx family is 125
°
C. With these two pieces of information, the maximum power dissipation can be
found by using
Example Calculation:
For example, what is the maximum input voltage that can be applied to a TPS727xx with a 1.5V output
voltage if the ambient temperature is 85
voltage if the ambient temperature is 85
°
C and the full 200mA of load current is required?
Given: T
J
= 125
°
C, T
A
= 85
°
C,
θ
JA
= 130
°
C/W
Using
, we substitute in the given values above and find that the maximum power dissipation
for the part is P
d
= 0.307W.
125
°
C = 85
°
C + P
d
(130
°
C/W)
(2)
This means that the total power dissipation of the TPS727xx must be less than 0.833W. Now the input
voltage can be calculated.
voltage can be calculated.
P
d
= (V
in
– V
out
)
×
I
out
= (Vin – 1.5V)
×
0.2A = 0.307W
(3)
So the maximum input voltage would need to be 3.04V or less in order to maintain a safe junction
temperature.
temperature.
Similar analysis can be performed to determine the maximum input voltage at room temperature (25
°
C) or
85
°
C to provide full output current while maintaining the junction temperature at or below 125
°
C. The
answer will depend on the output voltage.
Ambient
Temperature
VOUT
25
°
C
85
°
C
1.5
5.35
3.04
1.8
5.50
(1)
3.34
2.8
5.50
(1)
4.34
(1)
limited by recommended operating maximum, not thermal
SLVU325 – August 2009
TPS727xxDSEEVM-406
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