參數(shù)資料
型號: TS68882MF16
廠商: ATMEL CORP
元件分類: 數(shù)學(xué)處理器
英文描述: CMOS Enhanced Floating-point Co-processor
中文描述: MATH COPROCESSOR, CQFP68
封裝: CERAMIC, QFP-68
文件頁數(shù): 8/43頁
文件大?。?/td> 1414K
代理商: TS68882MF16
8
TS68882
2119A
HIREL
04/02
Thermal
Characteristics
Power
Considerations
The average chip-junction temperature, T
J,
in
°
C can be obtained from:
T
J
= T
A
+ (P
D
+
θ
JA
)
T
A
= Ambient Temperature,
°
C
θ
JA
= Package Thermal Resistance, Junction-to-Ambient,
°
C/W
P
D
= P
INT
+ P
I/O
P
INT
= I
CC
x V
CC,
Watts - Chip Internal Power
P
I/O
= Power Dissipation on Input and Output Pins - User Determined
For most applications P
I/O
< P
INT
and can be neglected.
An Approximate relationship between P
D
and T
J
(if P
I/O
is neglected) is:
P
D
= K: (T
J
+ 273)
Solving equations (1) and (2) for K gives
(1)
(2)
K = P
D
. (T
A
+ 273) +
θ
JA
·
P
D
where K is constant pertaining to the particular part K can be determined from the equa-
tion (3) by measuring PD (at equilibrium) for a known T
A
. Using this value of K, the
values of P
D
and T
J
can be obtained by solving equations (1) and (2) iteratively for any
value of T
A
.
The total thermal resistance of a package (
θ
JA
) can be separated into two components,
θ
JC
and
θ
CA
, representing the barrier to heat flow from the semiconductor junction to the
package (case), surface (
θ
JC
) and from the case to the outside ambient (
θ
CA
). These
terms are related by the equation:
2
(3)
θ
JA
=
θ
JC
+
θ
CA
θ
JA
is device related and cannot be influenced by the user. However,
θ
CA
is user depen-
dent and can be minimized by such thermal management techniques as heat sinks,
ambient air cooling and thermal convection. Thus, good thermal management on the
part of the user can significantly reduce
θ
CA
so that
θ
JA
approximately equals
θ
JC.
Substi-
tution of
θ
JC
for
θ
JA
in equation (1) will result in a lower semiconductor junction
temperature.
(4)
Table 4.
Package
Symbol
Parameter
Value
Rating
PGA 68
θ
JA
Thermal Resistance - Ceramic Junction To Ambient
33
°
C/W
θ
JC
Thermal Resistance - Ceramic Junction To Case
4
°
C/W
CQFP
θ
JA
θ
JC
Thermal Resistance - Ceramic Junction To Ambient
33
°
C/W
Thermal Resistance - Ceramic Junction To Case
3
°
C/W
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