
FXO-HC33 Series
MTTF / FITS Calculations
Products are grouped together by process for MTTF calculations.
(All XpressO output and package types are manufactured with the same process)
Number of Parts Tested:
360 (120 of each output type: HCMOS, LVDS, LVPECL)
Number of Failures: 0
Test Temperature: 125°C
Number of Hours: 2000
MTTF was calculated using the following formulas:
[1.] Device Hours ( devhrs ) = (number of devices) x (hours at elevated temperature in °K)
[2.] MTTF ?
devhrs ? af ? 2
? 2
[3.] FITS =
Where:
Label
1
MTTF
Name
* 10 9
Formula/Value
e
) ? ( ? )
af
Acceleration Factor
(
eV
k
1 1
t 1 t 2
eV
k
t 1
t 2
Θ
r
χ 2
Activation Energy
Bolzman’s Constant
Theta
Failures
Chi-Square
0.40 V
8.62 X 10 -5 eV /°K
Operating Temperature (°K)
Accelerated Temperature (°K)
Confidence Level (60% industry standard)
Number of failed devices
statistical significance for bivariate tabular analysis [table look-
up] based on assumed Θ (Theta – confidence) and number of
failures (r) For zero failures (60% Confidence): χ 2 = 1.830
DEVICE-HOURS = 360 x 2000 HOURS = 720,000
e
?
ACCELERATION FACTOR =
(
0 . 40
8 . 625
) ? (
1 1
298 398
)
= 49.91009
MTTF = 720, 000 ? 49 .91009 ? 2 = 39,209,238 Hours
1 . 833
Failure Rate =
1 . 833
720 , 000 ? 49 . 91009 ? 2
= 2.55E-8
FITS = Failure Rate *1E9 = 26
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