ort82g5 Lattice Semiconductor Corp., ort82g5 Datasheet - Page 115

• Manufacturer Part Number: ort82g5
• Description: Xaui And Fc Fpscs
• Manufacturer: Lattice Semiconductor Corp.

Lattice Semiconductor
where T
ing the Θ
reading, T
°C/W.
Θ Θ Θ Θ
This is the thermal resistance from junction to case. It is most often used when attaching a heat sink to the top of
the package. It is defined by:
The parameters in this equation have been defined above. However, the measurements are performed with the
case of the part pressed against a water-cooled heat sink to draw most of the heat generated by the chip out the
top of the package. It is this difference in the measurement process that differentiates Θ
thermal resistance and is expressed in units of °C/W.
Θ
This is the thermal resistance from junction to board. It is defined by:
where T
on the right-hand side have been defined above. This is considered a true thermal resistance, and the measure-
ment is made with a water-cooled heat sink pressed against the board to draw most of the heat out of the leads.
Note that Θ
cussed by the JEDEC committee.
FPSC Maximum Junction Temperature
Once the power dissipated by the FPSC has been determined, the maximum junction temperature of the FPSC
can be found. This is needed to determine if speed derating of the device from the 85 °C junction temperature used
in all of the delay tables is needed. Using the maximum ambient temperature, T
the device, Q (expressed in °C), the maximum junction temperature is approximated by:
Package Thermal Characteristics
The thermal characteristics of the 484-ball PBGAM (fpBGA with heat spreader) used for the ORT42G5, the 680-
ball PBGAM (fpBGA with heat spreader) and the 680-ball fpBGA used for the ORT82G5 are available in the Ther-
mal Management section of the Lattice web site at www.latticesemi.com.
Heat Sink Vendors for BGA Packages
The estimated worst-case power requirements for the ORT42G5 and ORT82G5 are in the 3 W to 5 W range. Con-
sequently, for most applications an external heat sink will be required. Table 46 lists, in alphabetical order, heat sink
vendors who advertise heat sinks aimed at the BGA market.
JC
JB
C
B
JA
is the temperature of the board adjacent to a lead measured with a thermocouple. The other parameters
is the case temperature at top dead center, T
C
, is made with a thermocouple attached at top-dead-center of the case. ψ
JB
measurements described above, besides the other parameters measured, an additional temperature
is expressed in units of °C/W and that this parameter and the way it is measured are still being dis-
T
Jmax
Θ
Θ
= T
JC
JB
Amax
=
=
J
115
is the junction temperature, and Q is the chip power. Dur-
T
T
J
J
+ (Q ⋅ Θ
ORCA ORT42G5 and ORT82G5 Data Sheet
– T
– T
Q
Q
C
B
JB
)
Amax
JC
, and the power dissipated by
is also expressed in units of
JC
from ψ
JC
. Θ
JC
is a true
(3)
(4)
(5)