Electronic circuits that provide sa

Electronic circuits that provide safety critical functions shall be– reliable and– not susceptible to loss of safety critical function due to exposure to electromagnetic environmental stresses encountered in anticipated environments.Compliance is checked by exposing these electronic circuits to the immunity tests described in– 18.8.2 to 18.8.6 for electronic circuits with no internal clock frequency or oscillator frequency higher than 15 MHz;– 18.8.2 to 18.8.7 for all other electronic circuits;which shall be passed without a loss of the safety critical function. The tests are carried out with the tool supplied at rated voltage or the mean value of the rated voltage range, unless the difference between the upper and lower limit of the rated voltage range is greater than 20 % of the mean value of the range, in which case the test is conducted at both the upper and lower limits of the rated voltage range.In addition, these electronic circuits shall be evaluated using the fault conditions of 18.6.1 but shall not result in a loss of any safety critical function or shall place and maintain the tool into a safe state while the fault condition is present. If the concept of 18.6.1 is not appropriate due to the design of the electronic circuit (e.g. in the case of a single channel design), then its reliability shall be evaluated by the methods of ISO 13849-1. Required performance levels for applicable safety critical functions are specified by the relevant part of IEC 62841-2, IEC 62841-3 or IEC 62841-4. Typical safety critical functions are indicated in Table 4.