U1AFS250-FG256 Datasheet, PDF (7/27 Pages) Actel Corporation – 3 - DC and Power Characteristics

Actel Fusion Mixed-Signal FPGA for the MicroBlade AdvancedMC Solution
Thermal Characteristics
Introduction
The temperature variable in the 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 temperature to be higher than the
ambient, case, or board temperatures. EQ 3-1 through EQ 3-3 give the relationship between
thermal resistance, temperature gradient, and power.
θ_JA
=
-^T---^J---^–----^θ----^A-
P
θ_JB
=
T_----J---–_----T_----B-
P
EQ 3-1
θ_JC
=
T_----J---–_----T_----C-
P
EQ 3-2
where
θ_JA = Junction-to-air thermal resistance
θ_JB = Junction-to-board thermal resistance
θ_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
EQ 3-3
Table 3-6 • Package Thermal Resistance
Product
U1AFS250-FG256
θ_JA
Still Air
1.0 m/s
2.5 m/s
θ_JC
33.7
30.0
28.3
9.3
U1AFS600-FG256
28.9
25.2
23.5
6.8
U1AFS1500-FG256
23.3
19.6
18.0
4.3
θ_JB
Units
24.8
°C/W
19.9
°C/W
14.2
°C/W
Preliminary v0.4
3-7