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Obtaining Early Analog Block Area Estimates

Obtaining Early Analog Block Area Estimates
by Tom Simon on 07-13-2021 at 6:00 am

I’ve written before about Pulsic’s Animate Preview software, which is extremely helpful in completing placement in analog blocks so that they are ready for routing. Analog design automation has always been a tough proposition, but Animate Preview looks like a promising tool, with practical benefits. Obtaining DRC clean placement that meets many of analog design’s complicated constraints is a huge win. Interestingly the team at Pulsic found another benefit derived from having good placement rapidly available.

Anyone who has done an SOC floorplan knows how hard it is to get good size estimates for analog blocks. Without good estimates for the analog content, figuring out the overall floor plan for an SOC is nearly impossible. Both over- and under-estimates can wreak havoc on an SOC floor plan. Late arrival of accurate analog block area information can disrupt SOC development schedules.

Animate preview, it turns out, is really good at estimating the final size of analog blocks at the start of the design process. I recently had the chance to read a paper on how Pulsic’s Animate Preview can improve analog block area estimation as compared to commonly employed estimation methods. The paper titled “Analog Integrated Circuit Design Area Estimation” surveys 280 commercially developed analog blocks to see how existing estimation methods stack up to Animate Preview.

The circuits used cover a wide variety of foundries and fabrication processes. These ranged from 0.8um to 28nm. There were many different types of commonly used blocks, such as DAC, ADC, bandgaps, amplifiers, comparators, etc. They used hand-crafted layout data that was DRC clean and fully verified as the reference.

The rule of thumb estimates that they applied were off by as much as a factor of 8x. The standard deviation was around a factor of 4.14. Given that the error in area can also be expressed in the x or y direction the reliability of areas estimates derived this way are extremely unreliable. When Pulsic’s Animate Preview was used to estimate block area the results were far closer to those seen in the final hand crafted blocks. The standard deviation of the error factor was 0.57. The paper goes into much more detail on how these conclusions were reached, with a thorough discussion on how to interpret the results.

Yet, the most interesting point for me was that Pulsic is making the area estimation capability of Animate Preview available to the design community for free. This is to say that anyone can download the software and execute a no-fee license agreement to run the software. The free version, of course, has limitations on what users can save off. With the free version users can save the block outline and pin positions.

Animate Preview Area Estimation
Animate Preview Analog Block Area Estimation

The “Plus” version, which is paid, can save out schematic driven layout, well shapes, guard rings, poly heads, and device & pCell placement. It comes with full support as well. Yet for free, users can gain a big benefit and perhaps see the value of the “Plus” version. So called Freemium software has not been seen a lot in EDA. Here we have an innovative tool that can be brought into almost any design flow where predicting analog block sizes is important. For more information on using Animate Preview for analog block size estimation look at the Pulsic website.

 

 

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