A simultaneous switching noise design algorithm for leadframe packages with or without ground plane

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 prespecified 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 leadframe design to meet prespecified 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 28×28 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