By reviewing the maximum ambient operating temperatures, it can be seen that by
using the all-small-buffer configuration of the TS68040 with a relatively small amount of
air flow (100 LFM), a 0-70°C ambient operating temperature can be achieved. However,
depending on the output buffer configuration and available forced-air cooling, additional
thermal management techniques may be required.
Thermal Characteristics with
a Heat Sink
In choosing a heat sink the designer must consider many factors: heat sink size and
composition, method of attachment, and choice of a wet or dry connection. The follow-
ing paragraphs discuss the relationship of these decisions to the thermal performance of
the design noticed during experimentation.
The heat sink size is one of the most significant parameters to consider in the selection
of a heat sink. Obviously a larger heat sink will provide better cooling. However, it is less
obvious that the most benefit of the larger heat sink of the pin fin type used in the exper-
imentation would be at still air conditions. Under forced-air conditions as low as 100
LFM, the difference between the ΦCA becomes very small (0.4°C/W or less). This differ-
ence continues to decrease as the forced air flow increases. The particular heat sink
used in our testing fit the perimeter package surface area available within the capacitor
pads on the TS68040 (1.48" x 1.48") and showed a nice compromise between height
and thermal performance needs. The heat sink base perimeter area was 1.24" x 1.30"
and its height was 0.49". It was a pin-fin-type (i.e. bed of nails) design composed of Al
alloy. The heat sink is shown in Figure 5 can be obtained through Thermalloy Inc. by ref-
erencing part number 2338B.
Figure 5. Heat Sink Example