Product Maturity 1

3Derating Analysis

3.1. Derating

Derating is conducted according to rules that preserve a “safety margin” (robustness) in terms of the maximum values of components guaranteed by manufacturers, in the case of operational constraints (electric overloads, disruptions, overheating, etc.) or in the case of errors or accidents while in use.

From a theoretical viewpoint, derating is defined by the following equation:

[3.1]

Let us illustrate this by considering the example of a capacitor whose manufacturer guarantees a maximum voltage of 50 V. If, in the application concerned, a voltage of 20 V is applied, the derating will be 20/50 = 40%. In order to check if this derating is acceptable, the derating rules must be clarified.

Derating has a positive impact on the reliability of components. Consider the three types of failures mentioned in Chapter 1. It is clear that derating has little to no influence on youth failures because they are generally the result of manufacturing errors.

However, derating has some influence on catastrophic failures. It is important to recall that the latter are normally the result of accidental overloads, for example, overvoltage. If we return to the example of the capacitor mentioned above, we see that, in certain cases, derating may prevent a failure from occurring if the value of the overvoltage remains below the guaranteed maximum voltage. Similarly, a ...