Power Planning

• Now it is time to plan and create power and ground structures for both I/O pads and core logic.
• The I/O pads’ power and ground buses are built into the pad itself and will be connected by abutment.
• For core logic, there is a core ring enclosing the core with one or more sets of power and ground rings.
• A horizontal metal layer is used to define the top and bottom sides, or any other horizontal segment, while the vertical metal layer is utilized for left, right, and any other vertical segment.
•  These vertical and horizontal segments are connected through an appropriate via cut.
• The next consideration is to construct the standard cell power and ground that is internal to the core logic.
• Each of these power and ground strips run vertically, horizontally, or in both directions.
• If these strips run both vertically and horizontally at regular intervals, then the style is known as power mesh.
• The total number of strips and interval distance is solely dependent on the ASIC core power consumption. As the ASIC core power consumption (dynamic and static) increases, the distance of power and ground strip intervals increases.
• This increase in the power and ground strip intervals is used mainly to reduce overall ASIC voltage drop, thereby improving ASIC design performance.
• In addition to the core power and ground ring, macro power and ground rings need to be created using proper vertical and horizontal metal layers.
• A macro ring encloses one or more macros, completely or partially, with one or more sets of power and ground rings.
• It is strongly recommended to check for power and ground connectivity and/or any physical design rule violations after construction of the entire power and ground network.
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Goal of power Planning is to provide power to all macros and standard cells within the given IR-Drop limit.

Power planning management can be divided in two major category :

• core cell power management
• I/O cell power management.

In core cell power planning power rings are formed around the core and macro.

In IO cell power planning power rings are formed for I/O cells and trunks are created between core power ring and power pads.

Power planning is part of floor plan stage. 

Input Required In Power Planning

1. Database with valid floorplan.

2. power rings and power straps width.

3. Spacing between VDD and VSS Straps.

Output Of Power Planning

Design with Power Structure