Anasim

August 2010: Early PI-aware design is a significant aspect of IC floorplanning, particularly in nanoscale systems where low power/energy and efficient use of chip/pkg metal and decoupling resources are key design constraints. The advent of 3D integration in the form of chip or package stacking makes early front-end analysis of PI through high levels of abstraction and physics-based simulations all the more necessary. Correlation between PI and thermal issues provides an added benefit in front-end PI analysis and optimization…

Continue reading in an SOCcentral featured article. More on power integrity and floorplanning: Anasim’s PI book for IC’s.

_______________

June 2010: Power Integrity (PI) analysis has traditionally been conducted using lumped, discrete elements and circuits, which lead to exponential simulation complexity, approximate models, and often, inaccurate results. In continuum-models based analysis, a chip power grid and distribution network is modeled as a continuous surface, employing distributed models for circuits and capacitance. This not only eliminates the exploding computational complexity for PI analysis in nanoscale chips, it facilitates physical, true-electromagnetic simulations for chips, packages, and 3D assemblies. Continuum-models based analysis is “analog” in the sense that a layer to be analyzed is treated as a spatial potential or voltage continuum, similar to analog signals being time-continuous in nature, as opposed to analyzing discrete elements and their interactions.

Read more on this in a SOCcentral featured article. A comprehensive treatment of Continuum Modeling is accessible in Anasim’s PI book for IC’s.

_______________

As simulation complexity in the number of elements explodes in the nanoscale regime (sub-100nm), tools face a difficult choice in reducing simulation times, where model accuracy is compromised. Tools employing model simplifications commonly claim 5% SPICE accuracy, or worse, which consumes design margin available for power integrity, and adds uncertainty. Besides, model simplification with large numbers of interacting inductors and capacitors is a complex task.

pi-fp, with continuum modeling, and distributed electrical parameters, load, and capacitance modeling, does not compromise simulation accuracy for speed, but reduces simulation resolution instead. By increasing the unit area simulated, from 50u by 50u to 100u by 100u, simulation speed in pi-fp is enhanced by at least a factor of 4, with no loss of grid voltage variation accuracy.

For more information: pi-fp brochure

RLCSim is a Windows(tm) executable that performs noise analysis on a power grid over a circuit block. This tool, a pre-cursor of pi-fp, considers grid resistance (IR drop), inductance (L*di/dt) or voltage droop, and distributed capacitance that absorbs transients, and displays noise propagation and summing within the block.

Inputs include grid parameters, block power consumption profiles and capacitance.

FREE RLCSim Windows(tm) ZIP Download

Shown below is a noise simulation result using RLCSIM demonstrating detrimental effects of lens-shaped on-chip decoupling capacitance structure. Power grid noise from an on-chip source is focused behind the capacitance structure, illustrating distributed true-electromagnetic simulation capability absent in other power integrity analysis tools.

Download a full-size version of the animation here

Download/View (PDF): Effective Current Density.pdf