Reducing EMI Using Spread Spectrum Clock Generators

Electromagnetic Interference describes the Electromagnetic emission coming from a system or specific devices that interferes with the operation of other secondary devices or systems. EMI is caused by electromagnetic induction or electromagnetic radiation emitted from a device.

With the trend to faster clock rates in systems with lower voltage and power together with the increased usage of wireless systems it has become very important to control EMI.

Reduction of the interference from the EMI source is one method to achieve compliance. This can consist of reducing the signal level of the source together with careful system designs and filtering. Other active methods can give improved results including frequency modulation of the source clocks.

Spread spectrum clock generation is used to reduce the radiated emissions from narrow band clocks by spreading the energy over a wider band and thus lowering the radiated emissions. This is an active solution which preserves the clock signal integrity and forms a relatively low-cost solution to reducing EMI.

 Centre spread Non-Modulated and Modulated clocks