8.1.1 External Component Selection Criteria

The Supporting Component Requirements table in each application description section lists the details of the supporting required components in each of the System Application Schematics. Where possible, the supporting component requirements have been consolidated to minimize the number of unique components which are used in the design. Component list consolidation is a method to reduce the number of unique part numbers in a design. Consolidation is done to ease inventory management and reduce the manufacturing steps during board assembly. For this reason, some capacitors are specified at a higher voltage than what would normally be required. An example of this is a 50-V capacitor can be used for decoupling of a 3.3-V power supply net.

In this example, a higher voltage capacitor can be used even on the lower voltage net to consolidate all caps of that value into a single component type. Similarly, several unique resistors, all having the same size and value but different power ratings can be consolidated by using the highest rated power resistor for each instance of that resistor value.

While this consolidation can seem excessive, the benefits of having fewer components in the design can far outweigh the trivial cost of a higher voltage capacitor. If lower voltage capacitors are already available elsewhere in the design, they can be used instead of the higher voltage capacitors. In all situations, the voltage rating of the capacitors must be at least 1.45 times the voltage of the voltage which appears across them. The power rating of the capacitors should be 1.5 times to 1.75 times the power dissipated in the capacitors during normal use case.