Terry Jernberg

Tips for reducing resonance and SSN.

Fast interfaces and switching speeds are becoming commonplace, and with them comes increased noise, amplifying any problems within the power delivery network. Products today are the direct result of the fast signal capabilities in current technology, making it impossible to eliminate noise. This noise can be seen in the form of simultaneous switching noise, which resonates and can combine to destroy the voltage signal and collapse the signal eye. Therefore, the only viable option is to mitigate the noise via containment.

Ground is the point from which every measurement is evaluated. Therefore, any variation will affect timing and voltage. Every signal switching on the board, whether slow or fast, contributes to noise on the power and ground planes. This “ground bounce” is commonly referred to as simultaneous switching noise (SSN) and is essentially crosstalk on the ground (FIGURE 1).



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