Abstract
This paper provides design techniques for leadframe packages with or without a ground plane, which enable an accurate estimate of the maximum Simultaneous Switching Noise (SSN) and the required numbers of power and/or ground pins for pre-specified SSN limits early in the design phase. Two heuristic design approaches, namely equal-angle and quarter-plane, are proposed as initial design choices for the lead frame design to meet pre-specified SSN constraint. Effects of the signal conductors in reducing the effective inductance of a leadframe package are quantified. Closed-form equations and SPICE simulation are used to calculate the Simultaneous Switching Noise. A design example for a 28/spl times/28 mm Plastic Quad Flat Package (PQFP) is given to provide guidelines for SSN-constrained design. The design algorithm is integrated into a CAD tool, UASSNS3.0, which is capable of initial SSN design of leadframe packages.
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