MAX785 Ver la hoja de datos (PDF) - Maxim Integrated
Número de pieza
componentes Descripción
Fabricante
MAX785 Datasheet PDF : 24 Pages
| |||
Product Reliability Report
Where:
T1 = 70°C + 273°C = 343°K
T2 = 150°C + 273°C = 423°K
Substituting for T1 + T2 and solving for e yields the
result:
Acceleration Factor = 165
The acceleration factor between 150°C and 70°C
is 165.
Appendix 2:
_____________________Determining Failure Rate
Definition of Terms
The Mean Time Between Failures (MTBF) is the
average time it takes for a failure to occur. For exam-
ple, assume a company tests 100 units for 1000 hrs.
The total device-hours accrued would be 100 x
1000, or 100,000 device-hours. Now assume two
units were found to be failures. Roughly, it could be
said that the MTBF would equal:
MTBF =
Total Device Hrs.
Total No. of Failures
=
100,000
2
=
50,000 hrs.
The Failure Rate (FR) is equal to the reciprocal of
the MTBF, or:
FR =
1
MTBF
=
1
50,000
= 0.00002
If this number is multiplied by 1 x 105, the failure
rate in terms of percent per 1000 hrs. is obtained;
i.e., 2%.
A common reliability term also used to express the
failure rate is Failures-in-Time, or FIT. This is the
number of failures per billion device-hours, and is
obtained by dividing the Failure Rate by 10-9:
FR = FIT.
10-9
Using the above example:
FIT = 0.00002/10-9
= 20,000
The FIT rate is, therefore, shorthand for the number
of units predicted to fail in a billion (10-9) device-
hours at the specified temperature.
Calculating Failure Rates and FITs
The failure rate can be expressed in terms of the
following four variables:
A = The number of failures observed after test
B = The number of hours the test was run
C = The number of devices used in the test
D = The temperature acceleration factor
(see Appendix 1)
Using data in Table 2, a failure rate at 25°C can
now be calculated:
A = 57
B = 192
C = 25,169
D = 9822 (Assuming Ea = 0.8eV, and a test
temperature of 150°C)
Substituting:
FR =
57
192 x 25,169 x 9822
=
1.20
x 10-9
Expressing this in terms of the FIT rate:
FIT = 1.20
To determine the FIT rate at a new temperature, the
acceleration factor (D) must be recalculated from
the Arrhenius equation given in Appendix 1.
Including Statistical Effects
in the FIT Calculation
Because a small random sample is being chosen
from each lot, the statistical effects are significant
enough to mention. With most published failure rate
figures, there is an associated confidence level
number. This number expresses the confidence
level that the actual failure rate of the lot will be
equal to or lower than the predicted failure rate.
The failure rate calculation, including a confidence
level, is determined as follows:
FR =
X2
2DH
Where:
X2 = the Chi square value
2DH = 2 times the total device hours
= 2 x (B x C x D)
20 _____________________________________________________________________________________
Share Link: 