5

AT91M55800A

1727E–ATARM–01/04

Thermal and Reliability

Considerations

Thermal Data

In Table 5, the device lifetime is estimated with the MIL-217 standard in the “moderately

controlled” environmental model (this model is described as corresponding to an instal-

lation in a permanent rack with adequate cooling air), depending on the device Junction

Temperature. (For details see the section “Junction Temperature” on page 6.)

Note that the user must be extremely cautious with this MTBF calculation: as the MIL-

217 model is pessimistic with respect to observed values due to the way the data/mod-

els are obtained (test under severe conditions). The life test results that have been

measured are always better than the predicted ones.

Table 6 summarizes the thermal resistance data related to the package of interest.

Reliability Data

The number of gates and the device die size are provided for the user to calculate reli-

ability data with another standard and/or in another environmental model.

Table 5. MTBF Versus Junction Temperature

Estimated Lifetime (MTBF) (Year)

100

25

125

14

150

8

175

5

Table 6. Thermal Resistance Data

Symbol

Parameter

Condition

Package

Typ

Unit

θ

JA

Junction-to-ambient thermal

resistance

Still Air

TQFP176

21

°C/

W

PBGA176

66

θ

JC

Junction-to-case thermal resistance

TQFP176

9.2

PBGA176

20.1

Table 7. Reliability Data

Parameter

Data

Unit

Number of Logic Gates

524

K gates

Number of Memory Gates

400

K gates

Device Die Size

29.0