Kontron SMARC-sA3874i - Manual (Page 73)

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User’s Guide
The table below describes the function and assembly hardware required by each of the heatspreader holes.
Hole Heatspreader ULP-COM sSA3874I Evaluation Carrier
A
3mm standoffs
Clearance for M2.5
Clearance holes M2.5 Threaded Standoffs
B Clearance for M2.5
3mm captive standoff
M2.5 thread
N/A
C M3 thread N/A N/A
6.3 Thermal Parameters
The TI Cortex A8 SoC thermal parameters are shown in the table below:
Description Detail
Junction Temperature(Tj) -40 0 C to 90 0 C (Industrial temp grade)
Thermal Resistance, CPU Junction to ambient (θ
JA
) 11.67 0 C/W
Thermal Resistance, CPU Junction to case (θ
JC
) 0.39 0 C/W
Thermal Resistance, CPU case to heat spreader far surface (θcs) Less than 1 0 C/W
A heat spreader is available now from Kontron for the sA3874i Module. A passive heat sink solution is also
available.
6.4 Operation without a Heat Spreader / Heat Sink
The ULP-COM sA3874i Module is sometimes used in a room temperature environment without any heat sink at all.
While it is easy and convenient, it is not generally recommended, as it can put the CPU die at or above the 90
0 C
limit, depending on what you are running and how system performance parameters (CPU speed, etc.).
At the Linux desktop, without any heat sinking at all, assuming a typical SOC power consumption of 5W and an
ambient room temperature of 23
0 C, with all SOC features enabled, the CPU die would be at about 81.5 0 C (5W *
11.7 0 C/W + 23 0 C). This is OK, but there is not much margin. A higher CPU load can push the temperature over
the 90 0 C limit.