2
Table 2. Reliability Predictions
Demonstrated Performance
Ambient
Temperature
(°C)
Junction
Temperature
[3]
(°C)
Performance in Time (60% Condence) Performance in Time (90% Condence)
MTBF
[1]
Failure Rate
[2]
(%/1K Hours) MTBF
Failure Rate
(%/1K Hours)
85 110 86100 1.161 34300 2.915
80 109 88800 1.126 35400 2.825
75 108 91700 1.091 36500 2.740
70 103 109100 0.917 43400 2.304
65 98 130500 0.766 52000 1.923
60 93 156900 0.637 62400 1.603
55 88 189500 0.528 75400 1.326
50 83 230200 0.434 91600 1.092
45 78 281200 0.356 111900 0.894
40 73 345400 0.290 137500 0.727
35 68 426800 0.234 169900 0.589
30 63 530800 0.188 211300 0.473
25 58 664600 0.150 264500 0.378
Notes:
[1] The 60% or 90% condence MTBF represents the minimum level of reliability performance which is expected from 60% or 90% of all samples. The
condence level is established based on the chi-square distribution.
[2] Failure rate (%/1K Hours) is 1/MTBF x 10
5
, assuming the failures are exponentially distributed.
[3] Data generated based on 55°C, 20mA and θJA = 780°C/W
Example of Failure Rate Calculation
Assume a device operating 8 hours/day, 5 days/week. The utilization factor, given 168hours/week is:
(8hous/day) x (5 days/week) / (168 hours/week) = 0.25
The point failure rate per year (8760 hours) at 75°C ambient temperature is:
(1.091% / 1K hours) x 0.25 x (8760 hours/year) = 2.39% per year
Similarly, 90% condence level failure rate per year at 75°C:
(2.74% / 1K hours) x 0.25 x (8760 hours/year) = 6.00% per year.