參數(shù)資料
型號: TS68040DESC01XCA
廠商: ATMEL CORP
元件分類: 微控制器/微處理器
英文描述: Third- Generation 32-bit Microprocessor
中文描述: 32-BIT, 25 MHz, MICROPROCESSOR, CPGA179
封裝: CERAMIC, PGA-179
文件頁數(shù): 12/49頁
文件大?。?/td> 1637K
代理商: TS68040DESC01XCA
12
TS68040
2116A–HIREL–09/02
To calculate the specific power dissipation of a specific design, the termination method
of each signal must be considered. For example, a signal output that is not connected
would not dissipate any additional power if it were configured in the large buffer rather
than the small buffer mode.
Relationships Between
Thermal Resistances and
Temperatures
Since the maximum operating junction temperature has been specified to be 125°C.
The maximum case temperature, TC, in °C can be obtained from:
T
C
= T
J
- P
D
·
Φ
JC
where:
(2)
T
C
T
J
P
D
Φ
JC
In general, the ambient temperature, T
A
, in °C is a function of the following formula:
T
A
= T
J
- P
D
·
Φ
JC
- P
D
·
Φ
CA
Where the thermal resistance from case to ambient,
Φ
CA
, is the only user-dependent
parameter once a buffer output configuration has been determined. As seen from equa-
tion (3), reducing the case to ambient thermal resistance increases the maximum
operating ambient temperature. Therefore, by utilizing such methods as heat sinks and
ambient air cooling to minimize the
Φ
CA
, a higher ambient operating temperature and/or
a lower junction temperature can be achieved.
= Maximum case temperature
= Maximum junction temperature
= Maximum power dissipation of the device
= Thermal resistance between the junction of the die and the case
(3)
However, an easier approach to thermal evaluation uses the following formulas:
T
A
= T
J
- P
D
·
Φ
JA
or alternatively,
(4)
T
J
= T
A
- P
D
·
Φ
JA
where:
(5)
Φ
JA
= thermal resistance from the junction to the ambient (
Φ
JC
+
Φ
CA
).
This total thermal resistance of a package,
Φ
JA
, is a combination of its two components,
Φ
JC
and
Φ
CA
. These components represent the barrier to heat flow from the semicon-
ductor junction to the package (case) surface (
Φ
JC
) and from the case to the outside
ambient (
Φ
JC
). Although
Φ
JC
is device related and cannot be influenced by the user,
Φ
CA
is user dependent. Thus, good thermal management by the user can significantly
reduce
Φ
CA
achieving either a lower semiconductor junction temperature or a higher
ambient operating temperature.
Thermal Management
Techniques
To attain a reasonable maximum ambient operating temperature, a user must reduce
the barrier to heat flow from the semiconductor junction to the outside ambient (
Φ
JA
).
The only way to accomplish this is to significantly reduce
Φ
CA
by applying such thermal
management techniques as heat sinks and ambient air cooling.
The following paragraphs discuss some results of a thermal study of the TS68040
device without using any thermal management techniques; using only air-flow cooling,
using only a heat sink, and using heat sink combined with air-flow cooling.
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