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33.2 Thermal Characteristics
Table 33-2 lists thermal resistance values.
Junction to ambient, natural convection
Junction to ambient (@200 ft/min)
Junction to board
Junction to case
Junction to top of package
1
θ
and Ψ
parameters are simulated in accordance with EIA/JESD Standard 51-2 for natural convection.
JMA
jt
Motorola recommends the use of θ
junction temperatures from exceeding the rated specification. System designers should be aware that device
junction temperatures can be significantly influenced by board layout and surrounding devices. Conformance to
the device junction temperature specification can be verified by physical measurement in the customer's system
using the Ψ
parameter, the device power dissipation, and the method described in EIA/JESD Standard 51-2.
jt
2
Per JEDEC JESD51-6 with the board horizontal.
3
Thermal resistance between the die and the printed circuit board per JEDEC JESD51-8. Board temperature is
measured on the top surface of the board near the package.
4
Thermal resistance between the die and the case top surface as measured by the cold plate method (MIL
SPEC-883 Method 1012.1).
5
Thermal characterization parameter indicating the temperature difference between package top and the junction
temperature per JEDEC JESD51-2. When Greek letters are not available, the thermal characterization parameter
is written as Psi-JT.
The average chip-junction temperature (T
Where:
T
= Ambient Temperature, ×C
A
Q
= Package Thermal Resistance, Junction-to-Ambient, ×C/W
JMA
P
= P
+ P
D
INT
I/O
P
= I
¥ V
INT
DD
P
= Power Dissipation on Input and Output Pins — User Determined
I/O
For most applications P
between P
and T
D
J
MOTOROLA
Table 33-2. Thermal Characteristics
Characteristic
Four layer board (2s2p)
Four layer board (2s2p)
Natural convection
and power dissipation specifications in the system design to prevent device
JA
T
=
T
J
A
, Watts - Chip Internal Power
DD
< P
and can be neglected. An approximate relationship
I/O
INT
(if P
is neglected) is:
I/O
Chapter 33. Electrical Characteristics
Symbol
) in °C can be obtained from:
J
(1)
(
×
Θ
)
+
P
D
JMA
Thermal Characteristics
Value
1,2
θ
26
JMA
1,2
θ
23
JMA
3
θ
15
JB
4
θ
10
JC
1,5
Ψ
2
jt
Unit
°C/W
°C/W
°C/W
°C/W
°C/W
33-3
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