User manual

ECE 477 Final Report Spring 2004
λ
p
= λ
b
π
R
π
Q
π
E
λ
b
takes into account both temperature and stress factors. If we go with earlier temperature
considerations, and assume high stress, 0.017 should be a safe base rate. However, maximum
stress cannot be calculated because at that assumed temperature, maximum would be beyond
tolerance, and our design may or may not push the line. Testing and measurements will tell, so
we will assume it is high. π
R
did not have a resistance in the range of the Power Resistor in our
design. Since it is less than 1Ω we will choose the closest range and use 1.0. Quality and
environmental standards are the same, except the constants are different in this table, making
them 3.0 and 10 respectively.
λ
p
= 0.017 * 1.0 * 3.0 * 10 = .51 x 10
-6
.
MTTF = 1/ λ
p
= 2.0x10
6
hours, or around 223 years, an iffy figure.
150uF Polarized Capacitor
The equation this time is:
λ
p
= λ
b
π
CV
π
Q
π
E
It is very similar to that of the resistor, except with a capacitance factor instead of a
resistance factor. For the Base Failure Rate, we will once again assume a similar high
temperature and high stress, since this is in the power supply, and get a rate of 0.077. This time,
there is no mention of being out of tolerance. The Capacitance Value will need to be calculated
by hand, since the value is high. The equation is
π
CV
= 1.1C (uF)
0.085
= 1.1 (150)
0.085
= 1.68.
Quality factors are still to be assumed on the low end and Environment still
mobile/ground, so the values in this case are both 10.
λ
p
= 0.077 * 1.68 * 10 * 10 = 12.9 / 10
6
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