Table 9. Thermal Parameters With Heat Sink and No Air Flow
Thermal Mgmt.
Technique
Defined Parameters
Heat Sink
PD
TJ
ΦJC
2338B
3W
125°C
1°C/W
2338B
5W
125°C
1°C/W
Measured
ΦJA
14°C/W
14°C/W
ΦCA
13°C/W
13°C/W
Calculated
TC
122°C
120°C
TA
83°C
55°C
Thermal Characteristics with
a Heat Sink
and Forced Air
A sample size of three TS68040 packages was tested in forced-air cooling in a wind tun-
nel with a heat sink. This test was performed with 3W of power being dissipated from
within the package. As mentioned previously, the variance in ΦJA within the possible
power range is negligible; it can be assumed for calculation purposes that ΦJA is valid at
all power levels. Table 10 shows the results, assuming a maximum power dissipation at
3 and 5W with air flow and heat sink thermal management (refer to Table 6 to calculate
other power dissipation values).
Table 10. Thermal Parameters with Heat Sink and Air Flow
Thermal Mgmt. Technique
Defined Parameters
Air-flow
Heat sink
PD
TJ
ΦJC
100 LFM
2338B
3W
125°C
1°C/W
250 LFM
2338B
3W
125°C
1°C/W
500 LFM
2338B
3W
125°C
1°C/W
750 LFM
2338B
3W
125°C
1°C/W
1000 LFM
2338B
3W
125°C
1°C/W
100 LFM
2338B
5W
125°C
1°C/W
250 LFM
2338B
5W
125°C
1°C/W
500 LFM
2338B
5W
125°C
1°C/W
750 LFM
2338B
5W
125°C
1°C/W
1000 LFM
2338B
5W
125°C
1°C/W
Measured
ΦJA
3.1°C/W
2.2°C/W
1.7°C/W
1.5°C/W
1.4°C/W
3.1°C/W
2.2°C/W
1.7°C/W
1.5°C/W
1.4°C/W
ΦCA
2.1°C/W
1.2°C/W
0.7°C/W
0.5°C/W
0.4°C/W
2.1°C/W
1.2°C/W
0.7°C/W
0.5°C/W
0.4°C/W
Calculated
TC
122°C
122°C
122°C
122°C
122°C
120°C
120°C
120°C
120°C
120°C
TA
115.7°C
118.4°C
119.9°C
120.5°C
120.8°C
109.5°C
114°C
116.5°C
117.5°C
118°C
Thermal Testing Summary
Testing proved that a heat sink in combination with a relatively small amount of air-flow
(100 LFM or less) will easily realize a 0-70°C ambient operating temperature for the
TS68040 with almost any configuration of the output buffers. A heat sink alone may be
capable of providing all necessary cooling, depending on the particular heat sink
height/size restraints, the maximum ambient operating temperature required, and the
output buffer configuration chosen. Also forced air cooling alone may attain a 0-70°C
ambient operating temperature. However this factor is highly dependent on the output
buffer configuration chosen and the available forced air for cooling. Figure 7 is a sum-
mary of the test results of the relationship between ΦJA and air-flow for the TS68040.
16 TS68040
2116A–HIREL–09/02