TS68040MFDSLASHT33A datasheet(13/49 Pages) ATMEL

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TS68040

2116A–HIREL–09/02

Thermal Characteristics in

Still Air

A sample size of three TS68040 packages was tested in free-air cooling with no heat

sink. Measurements showed that the average

JA was 22.8°C/W with a standard devia-

tion of 0.44°C/W. The test was performed with 3W of power being dissipated from within

the package. The test determined that

JA will decrease slightly for the increasing power

dissipation range possible. Therefore, since the variance in

JA within the possible

power dissipation range is negligible, it can be assumed for calculation purposes that

JA is valid at all power levels. Using the formulas introduced previously, Table 7 shows

the results of a maximum power dissipation of 3 and 5W with no heat sink or air-flow

(refer to Table 6 to calculate other power dissipation values).

As seen by looking at the ambient temperature results, most users will want to imple-

ment some type of thermal management to obtain a more reasonable maximum

ambient temperature.

Thermal Characteristics in

Forced Air

A sample size of three TS68040 packages was tested in forced air cooling in a wind tun-

nel with no heat sink. This test was performed with 3W of power being dissipated from

within the package. As previously mentioned, since the variance in

ΦJA within the possi-

ble power range is negligible, it can be assumed for calculation purposes that

JA is

constant at all power levels. Using the previous formulas, Table 8 shows the results of

the maximum power dissipation at 3 and 5W with air-flow and no heat sink (refer to

Table 6 to calculate other power dissipation values).

Table 7. Thermal Parameters With No Heat Sink or Air-flow

Defined Parameters

Measured

Calculated

CA = ΦJA - ΦJC

C = TJ - PD * ΦJC

A = TJ - PD * ΦJA

3 Watts

125°C

1°C/W

21.8°C/W

20.8°C/W

122°C

59.6°C

5 Watts

125°C

1°C/W

21.8°C/W

20.8°C/W

120°C

16°C

Table 8. Thermal Parameters With Forced Air Flow and No Heat Sink

Thermal Mgmt.

Technique

Defined Parameters

Measured

Calculated

Air-flow velocity

100 LFM

125°C

1°C/W

11.7°C/W

10.7°C/W

122°C

89.9°C

250 LFM

125°C

1°C/W

10°C/W

9°C/W

122°C

95°C

500 LFM

125°C

1°C/W

8.9°C/W

7.9°C/W

122°C

98.3°C

750 LFM

125°C

1°C/W

8.5°C/W

7.5°C/W

122°C

99.5°C

1000 LFM

125°C

1°C/W

8.3°C/W

7.3°C/W

122°C

100.1°C

100 LFM

125°C

1°C/W

11.7°C/W

10.7°C/W

120°C

66.5°C

250 LFM

125°C

1°C/W

10°C/W

9°C/W,

120°C

75°C

500 LFM

125°C

1°C/W

8.9°C/W

7.9°C/W

120°C

80.5°C

750 LFM

125°C

1°C/W

8.5°C/W

7.5°C/W

120°C

82.5°C

1000 LFM

125°C

1°C/W

8.3°C/W

7.3°C/W

120°C

83.5°C

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