The impact of split power planes on package performance

Abstract

The purpose of this study is to assess the impact of the split power planes on package performance. A non-custom package with 16 power plane splits is studied from the perspective of plane noise, trace impedance and trace crosstalk. 2D and 3D simulations are performed on the package using selected sections of the package. The plane noise is found not to be significant when there is either low or high driver transient current demand. In the low current demand case, current is primarily confined to the region of the plane beneath the trace and the transient plane voltage is small. In the high current demand case, guidelines are given to minimize the impact of the split planes. Among these guidelines, a minimum trace to plane split distance should be maintained such that the effective inductance is not increased. 2D simulations are performed to examine the impact of the split plane on the signal trace impedance. Signal trace impedance is found to vary depending on its proximity to the plane split. The impact of the plane splits on the signal trace crosstalk is investigated. Capacitive coupling between traces is reduced by distancing the signal trace from the plane split. 3D simulations using a subsection of the multiple split plane package are performed. Plots showing the near end and far end crosstalk for five traces distributed about a plane split are included. Crosstalk is found not to increase for traces bordering the plane split as long as a minimum trace to plane split distance is maintained.