When designing for compliance, don't shoot for the maximum compliance limits if they are not required - unless you know your design can easily make it. I've seen time wasted and money lost pursuing the 'best' limits because of the somewhat proud claim: "I want the best compliance achievable". No real value is gained, but precious resources and market timing are lost.

Here are some things to remember:

• Compliance is required in most countries before the product can be advertised, sold and exported/imported.
• Seek certification of Emissions and Susceptibility as required.
• Emissions and Susceptibility compliance is also required for interfaces to facility power systems.
• Design for compliance to loosest level required for the intended market.
• But, design for margin to cover production variances.
• Ensure the 'traceablity' of the compliance design and the production process.

Component/Circuit EMC Control
- First Line of Defense -

Believe it or not, some components, including some integrated circuits (ICs), are poorly designed for preventing EMI generation (or immunity); some IC designers are not systems designers and tend not to pay attention to issues outside the functioning of the chip. Therefore component selection can be a critical part of designing to prevent EMI. Note that any EMI problem at the component level can create EMI problems at the board and system.

Proper circuit design can also eliminate many EMI problems too. Following are some tips:

• Select EMC 'hardened' components.
• Control fundamental frequencies and minimize generated frequencies.
• Utilize EMI suppression techniques e.g.:
• Filtering & Impedance control components.
• Vendor suggested component Shielding.
• Adequate power & grounding paths.
• Isolation and balancing of 'noisy' components and circuits.
• Circuit simulation techniques are useful to gain a ballpark knowledge of where your designs can be optimized for compliance.