afs600 Actel Corporation, afs600 Datasheet - Page 232

• Manufacturer Part Number: afs600
• Description: Actel Fusion Programmable System Chips Mixed-signal Family With Optional Arm Support
• Manufacturer: Actel Corporation

Theta-JA
Junction-to-ambient
determined under standard conditions specified by
JEDEC (JESD-51), but it has little relevance in actual
performance of the product. It should be used with
caution but is useful for comparing the thermal
performance of one package to another.
A sample calculation showing the maximum power
dissipation allowed for the AFS600-FG484 package under
forced
temperature is as follows:
where
The power consumption of a device can be calculated
using the Actel power calculator. The device's power
consumption must be lower than the calculated
maximum power dissipation by the package. If the
power consumption is higher than the device's maximum
allowable power dissipation, a heat sink can be attached
on top of the case, or the airflow inside the system must
be increased.
Theta-JB
Junction-to-board thermal resistance (
ability of the package to dissipate heat from the surface
of the chip to the PCB. As defined by the JEDEC (JESD-51)
standard, the thermal resistance from junction to board
uses an isothermal ring cold plate zone concept. The ring
cold plate is simply a means to generate an isothermal
boundary condition at the perimeter. The cold plate is
mounted on a JEDEC standard board with a minimum
distance of 5.0 mm away from the package edge.
Theta-JC
Junction-to-case thermal resistance (
ability of a device to dissipate heat from the surface of
the chip to the top or bottom surface of the package. It
is applicable for packages used with external heat sinks.
Constant temperature is applied to the surface in
3 -8
θ
T
JA
A
Maximum Power Allowed
Actel Fusion Programmable System Chips
= 19.00°C/W (taken from
= 75.00°C
Maximum Power Allowed
convection
of
thermal
=
1.0 m/s
110.00°C 75.00°C
--------------------------------------------------- -
19.00°C/W
=
Table 3-6 on page
T
----------------------------------------- -
resistance
J(MAX)
and
–
θ
θ
JC
θ
JB
–
JA
) measures the
75°C
) measures the
T
A(MAX)
=
(
1.84 W
ambient
θ
JA
3-7).
EQ 3-4
)
A d v a n c e d v 1 .4
is
consideration and acts as a boundary condition. This only
applies to situations where all or nearly all of the heat is
dissipated through the surface in consideration.
Calculation for Heat Sink
For example, in a design implemented in an AFS600-
FG484
consumption value using the power calculator is 3.00 W.
The user-dependent T
From the datasheet:
The 2.35 W power is less than the required 3.00 W. The
design therefore requires a heat sink, or the airflow
where the device is mounted should be increased. The
design's
requirement can be estimated by
Determining the heat sink's thermal performance
proceeds as follows:
where
A heat sink with a thermal resistance of 5.01°C/W or
better should be used. Thermal resistance of heat sinks is
a function of airflow. The heat sink performance can be
significantly improved with increased airflow.
T
T
θ
θ
θ
θ
J
A
JA
JC
JA
SA
θ
=
=
SA
= 0.37°C/W
= Thermal resistance of the interface material
= Thermal resistance of the heat sink in °C/W
=
=
θ
ja(total)
=
package
110.00°C
70.00°C
between the case and the heat sink, usually
provided by the thermal interface manufacturer
17.00°C/W
8.28°C/W
13.33°C/W 8.28°C/W
P
total
=
=
T
---------------- -
T
---------------- -
J
θ
θ
θ
–
J
JA(TOTAL)
SA
JA
–
P
T
junction-to-air
with
T
A
–
=
A
a
=
θ
=
and T
JA(TOTAL)
110°C 70°C
---------------------------------- -
110°C 70°C
---------------------------------- -
=
2.5 m/s
17.00 W
θ
3.00 W
JC
j
are given as follows:
–
+
–
–
–
θ
0.37°C/W
θ
CS
EQ
JC
airflow,
+
–
thermal
=
3-6:
θ
θ
=
CS
SA
2.35 W
13.33°C/W
=
5.01°C/W
the
resistance
EQ 3-8
power
EQ 3-5
EQ 3-6
EQ 3-7