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Welcome back to my blog series—Virtuoso® Automated Device Placement and Routing. In my earlier blogs in this series, I had touched upon the two foundational blocks of this solution, automated grouping and constraint creation and automated generation of placement and routing grids. After these important requirements have been met, the design is ready to be placed and routed.
In this blog, I will focus on the automated placement step that is powered by an engine tailored specifically to meet the unique requirements and challenges of analog device-level layouts at advanced nodes.
On one hand, the placement caters to the analog layout style, with support for device groups and topological constraints. On the other hand, the placement follows a row-based, gridded methodology, placing the devices in rows and snapping them to grids, as required in these nodes.
One of the central pieces of the Automated Device Placement and Routing solution is the new device-level automatic placer, which lets you place devices and device groups in a constraint and grid compliant manner. As I have noted in my previous blogs, you can run any step in the Automated Device Placement and Routing solution with a single click with the default settings or you can tune the settings as per your needs.
In the case of placement, you can choose your placement objective—whether you intend to achieve a compact device placement, reduced wire length, or both. You can also choose to use the existing PR boundary or specify a custom aspect ratio. When you specify an aspect ratio, the placer adjusts the boundary and rows automatically to fit the resulting layout.
Let's now take a look at some of the unique features of this new automatic placer.
Of course, the automatic placer honors the constraints and minimizes the area and wire length for a given boundary or aspect ratio. It also follows rows and grids for advanced nodes. In addition, it partitions the placement based on the device types. Most importantly, the placer respects device groups while compacting and optimizing them such that the group aspect ratios are best suited for a given floorplan.
User control of the layout aspect ratio with automatic optimization of the groups is a key feature of the automatic placer. This helps you to iterate very quickly through multiple different layouts that follow the desired placement goals. You can then compare the results and choose the placement that best suits your requirements.
That's not all. Do you want to make minor tweaks to the way the devices are placed? We have a solution for that too…
You can use the interactive device placement options to place devices semi-automatically. You can control how the selected devices are placed using an automatic context menu. For example, you can group or ungroup the devices, restrict their placement to a specific direction (horizontal or vertical), and specify the spread direction of devices.
Here's an animation depicting how the automatic and interactive placers work.
Explore the various placement options to see how they work!
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