ProASIC3 DC and Switching Characteristics
v1.3 2-5
Thermal Characteristics
Introduction
The temperature variable in the Actel Designer software refers to the junction temperature, not
the ambient temperature. This is an important distinction because dynamic and static power
consumption cause the chip junction to be higher than the ambient temperature.
EQ 2-1 can be used to calculate junction temperature.
T
J
= Junction Temperature = ∆T + T
A
EQ 2-1
where:
T
A
= Ambient Temperature
∆T = Temperature gradient between junction (silicon) and ambient ∆T = θ
ja
* P
θ
ja
= Junction-to-ambient of the package. θ
ja
numbers are located in Table 2-5.
P = Power dissipation
Package Thermal Characteristics
The device junction-to-case thermal resistivity is θ
jc
and the junction-to-ambient air thermal
resistivity is θ
ja
. The thermal characteristics for θ
ja
are shown for two air flow rates. The absolute
maximum junction temperature is 100°C. EQ 2-2 shows a sample calculation of the absolute
maximum power dissipation allowed for a 484-pin FBGA package at commercial temperature and
in still air.
EQ 2-2
Maximum Power Allowed
Max. junction temp. (° C) Max. ambient temp. (° C)–
θ
ja
(° C/W)
-----------------------------------------------------------------------------------------------------------------------------------------
100° C70° C–
20.5° C/W
-------------------------------------- 1 . 4 6 3 W
·
===
Table 2-5 • Package Thermal Resistivities
Package Type Device Pin Count θ
jc
θ
ja
UnitsStill Air 200 ft./min. 500 ft./min.
Quad Flat No Lead A3P030 132 0.4 21.4 16.8 15.3 C/W
A3P060 132 0.3 21.2 16.6 15.0 C/W
A3P125 132 0.2 21.1 16.5 14.9 C/W
A3P250 132 0.1 21.0 16.4 14.8 C/W
Very Thin Quad Flat Pack (VQFP) All devices 100 10.0 35.3 29.4 27.1 C/W
Thin Quad Flat Pack (TQFP) All devices 144 11.0 33.5 28.0 25.7 C/W
Plastic Quad Flat Pack (PQFP) All devices 208 8.0 26.1 22.5 20.8 C/W
PQFP with embedded heatspreader All devices 208 3.8 16.2 13.3 11.9 C/W
Fine Pitch Ball Grid Array (FBGA) See note* 144 3.8 26.9 22.9 21.5 C/W
See note* 256 3.8 26.6 22.8 21.5 C/W
See note* 484 3.2 20.5 17.0 15.9 C/W
A3P1000 144 6.3 31.6 26.2 24.2 C/W
A3P1000 256 6.6 28.1 24.4 22.7 C/W
A3P1000 484 8.0 23.3 19.0 16.7 C/W
* This information applies to all ProASIC3 devices except the A3P1000. Detailed device/package thermal
information will be available in future revisions of the datasheet.
