Fusion Family of Mixed Signal FPGAs
Revision 4 3-7
Thermal Characteristics
Introduction
The temperature variable in the Microsemi Designer software refers to the junction temperature, not the
ambient, case, or board temperatures. This is an important distinction because dynamic and static power
consumption will cause the chip's junction temperature to be higher than the ambient, case, or board
temperatures. EQ 1 through EQ 3 give the relationship between thermal resistance, temperature
gradient, and power.
EQ 1
EQ 2
EQ 3
where
JA
= Junction-to-air thermal resistance
JB
= Junction-to-board thermal resistance
JC
= Junction-to-case thermal resistance
T
J
= Junction temperature
T
A
= Ambient temperature
T
B
= Board temperature (measured 1.0 mm away from the
package edge)
T
C
= Case temperature
P = Total power dissipated by the device
JA
T
J
A
–
P
------------------
=
JB
T
J
T
B
–
P
-------------------
=
JC
T
J
T
C
–
P
-------------------
=
Table 3-6 • Package Thermal Resistance
Product
JA
JC
JB
UnitsStill Air 1.0 m/s 2.5 m/s
AFS090-QN108 34.5 30.0 27.7 8.1 16.7 °C/W
AFS090-QN180 33.3 27.6 25.7 9.2 21.2 °C/W
AFS250-QN180 32.2 26.5 24.7 5.7 15.0 °C/W
AFS250-PQ208 42.1 38.4 37 20.5 36.3 °C/W
AFS600-PQ208 23.9 21.3 20.48 6.1 16.5 °C/W
AFS090-FG256 37.7 33.9 32.2 11.5 29.7 °C/W
AFS250-FG256 33.7 30.0 28.3 9.3 24.8 °C/W
AFS600-FG256 28.9 25.2 23.5 6.8 19.9 °C/W
AFS1500-FG256 23.3 19.6 18.0 4.3 14.2 °C/W
AFS600-FG484 21.8 18.2 16.7 7.7 16.8 °C/W
AFS1500-FG484 21.6 16.8 15.2 5.6 14.9 °C/W
AFS1500-FG676 TBD TBD TBD TBD TBD °C/W