SX-A Family FPGAs
v5.1
2-11
Thermal Characteristics
Introduction
The temperature variable in Actel 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 to be higher than the ambient, case, or board temperatures. EQ 2-9 and EQ 2-10 give the relationship
between thermal resistance, temperature gradient and power.
EQ 2-9
EQ 2-10
Where:
θ
JA
T
J
T
A
–
P
----------------
=
θ
JA
T
C
T
A
–
P
------------------
=
θ
JA = Junction-to-air thermal resistance
θ
JC = Junction-to-case thermal resistance
TJ
= Junction temperature
TA = Ambient temperature
TC = Ambient temperature
P
= total power dissipated by the device
Table 2-12 • Package Thermal Characteristics
Package Type
Pin
Count
θ
JC
θ
JA
Units
Still Air
1.0 m/s
200 ft./min.
2.5 m/s
500 ft./min.
Thin Quad Flat Pack (TQFP)
100
14
33.5
27.4
25
°C/W
Thin Quad Flat Pack (TQFP)
144
11
33.5
28
25.7
°C/W
Thin Quad Flat Pack (TQFP)
176
11
24.7
19.9
18
°C/W
Plastic Quad Flat Pack (PQFP)1
208
8
26.1
22.5
20.8
°C/W
Plastic Quad Flat Pack (PQFP) with Heat Spreader2
208
3.8
16.2
13.3
11.9
°C/W
Plastic Ball Grid Array (PBGA)
329
3
17.1
13.8
12.8
°C/W
Fine Pitch Ball Grid Array (FBGA)
144
3.8
26.9
22.9
21.5
°C/W
Fine Pitch Ball Grid Array (FBGA)
256
3.8
26.6
22.8
21.5
°C/W
Fine Pitch Ball Grid Array (FBGA)
484
3.2
18
14.7
13.6
°C/W
Notes:
1. The A54SX08A PQ208 has no heat spreader.
2. The SX-A PQ208 package has a heat spreader for A54SX16A, A54SX32A, and A54SX72A.
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