A SIMULTANEOUS SWITCHING NOISE DESIGN ALGORITHM FOR LEADFRAME PACKAGES WITH OR WITHOUT GROUND PLANE

This paper provides design techniques for leadframe packages with or w ithout a ground plane, which enable an accurate estimate of the maximu m simultaneous switching noise (SSN) and the required numbers of power and/or ground pins for prespecified SSN limits early in the design ph ase, Two heuristic design approaches, namely equal-angle and quarter-p lane, are proposed as initial design choices for the leadframe design to meet prespecified SSN constraint, Effects of the signal conductors in reducing the effective inductance of a leadframe package are quanti fied. Closed-form equations and SPICE simulation are used to calculate the simultaneous switching noise, A design example for a 28 x 28 mn p lastic quad flat package (PQFP) is given to provide guidelines for SSN -constrained design, The design algorithm is integrated into a CAD too l, UASSNS3.0, which is capable of initial SSN design of leadframe pack ages.