AN 766: Intel® Stratix® 10 Devices, High Speed Signal Interface Layout Design Guideline

ID 683132
Date 3/12/2019
Document Table of Contents

Sweeping Anti-pad Radius

Figure 39. Differential Return Loss and TDR Impedance Performances for 0201 AC Capacitors by Various Anti-pad SizesFigure shows a fixed rectangular GND cutout under the capacitors while changing only the signal via anti-pad radius.

Based on this TDR response, a larger via anti-pad eventually increases the impedance of the entire structure. Using a 22 mil anti-pad radius is an optimum solution for this case and results in the least mismatching.