Closed-Form Expressions for I/O Simultaneous Switching Noise Revisited.

Closed-form expressions to estimate power supply noise due to the simultaneous switching of I/O drivers are revisited in this brief. It is shown that existing closed-form expressions share a common limitation and underestimate noise with up to 83% error in advanced nanoscale technologies with fast signal rise/fall times. This characteristic is investigated, both quantitatively and qualitatively. New closed-form expressions are developed for the signals with fast transition times. Results demonstrate that the proposed closed-form expressions exhibit an average error of 3.3% as compared with SPICE simulations, and enhance the accuracy of the existing expressions by up to 79.4%.