Why Only MV When You Can MC, MM & MV?

Resistance is futile. I recently caved and switched to an iPhone after having been a loyal Google phone user for more than year. Apart from the coolness factor, my main motivation was corporate mail support that was absent in Gphone, plus the fact that I got the iPhone for free when my wife upgraded hers. The difference is day and night between the two phones – The iPhone UI is much friendlier, menu options are simple and logical and the device is much faster for certain applications like browsing, data download, and video capture. Most of the modern smart phones/PDA are increasingly employing the multi-voltage technique, specifically ‘dynamic voltage and frequency scaling’ (DVFS) to reduce power without sacrificing performance. The iPhone designers, unlike the Gphone have done a good job of creating this balance between the different applications running on the device.

Regardless of the phone type multi-voltage designs, unlike the vanilla designs, are difficult to implement because of the inherent complexity and the need to handle special cells such as level shifters and isolation cells. In addition, these design styles also cause the number of modes and corners to increase significantly when min/max voltage combinations from all the power domains are considered. Because each different voltage supply and operational mode implies different timing and power constraints on the design, multi-voltage methodologies cause the number of design corners to increase exponentially with addition of each domain or voltage island. DVFS further complicate matters with varying frequency and clock combinations leading to even more design modes and corners. Additionally, the worst case power corners don’t necessarily correspond to the worst case timing, so it’s critical to know how to pick a set of corners that will result in true optimization across all design objectives without excessive design margins.

So, what’s the story you might ask? It’s pretty simple (or not). In order to effectively close these multi-voltage designs across all modes, corners, timing, and power must be concurrently analyzed and optimized simultaneously for different combinations of library models, voltages, and interconnect (RC) corners. In essence, true and concurrent multi-corner multi-mode (MCMM) analysis and optimization is a pre-requisite for any multi-voltage design. Anything less would not guarantee convergence because optimization in one scenario could create a new violation in a different scenario, lead to multiple iterations, create unpredictable ECO loops, result in poor QoR and possibly reduce yield. In other words, low power designs, specifically MV designs, inherently require true MCMM optimization for both power and timing.

Now, will I go back to the Gphone? If and only if they support corporate mail and also improve the performance. It wouldn’t hurt to jack up the coolness factor either. Till then I will remain an iPhone user (loyal or not is debatable). The only problem with the iPhone is, quoting Seinfeld, “if you are mad at someone you cannot slam the iPhone, but instead you will have to slide the phone off.”

–Arvind Narayanan, Product Marketing Manager, Place and Route Product Line