How do you plan a usable voltage area?
From PDVerse PnR Interview Handbook · pdVerse Mentor Guide
Short Answer
Shape and size it for assigned cells, expected growth, legal rows, boundary cells, isolation/level-shifter/retention zones, switch corridors, macro compatibility, and supply access.
Technical Explanation
A voltage area is usable placement geography for one power intent, not a coloured box. Check target utilisation, enclosure, alignment, guard band if used, nested/overlap rules, row ownership, and access to neighbouring domains.
Formula Or Decision Rule
Decision rule: domain cells and required interface cells fit legally without stranded slivers.
What To Check
• Warning sign: The region encloses enough area but cuts rows into unusable fragments or blocks supplies. • Inspect: choose one affected region, macro, row, pin, path, or net and trace the physical cause. • Correct: Reshape or move the region, rebuild affected rows/boundaries, and rerun multivoltage and floorplan checks.
Command Checks & Actions
• create_voltage_area -power_domains <domain_list> -region <region_list> -target_utilization <ratio> -name <voltage_area>: creates a physical region for one or more power domains
• report_design -floorplan: reports the floorplan state understood by the tool
Run only the commands needed for this question. Save the report with the floorplan version and analysis context.Healthy, Suspicious & Hard-stop Results
• Healthy: Shape and size it for assigned cells, expected growth, legal rows, boundary cells, isolation/level-shifter/retention zones, switch corridors, macro compatibility, and supply access. • Suspicious: The region encloses enough area but cuts rows into unusable fragments or blocks supplies. • Hard stop: required legality or physical feasibility is missing or unexplained. Reshape or move the region, rebuild affected rows/boundaries, and rerun multivoltage and floorplan checks.
Common Mistake
Do not hide the symptom with an arbitrary utilisation, halo, channel, blockage, pin move, or die-size change. The region encloses enough area but cuts rows into unusable fragments or blocks supplies.
What The Interviewer Is Testing
The interviewer is testing whether you can connect “How do you plan a usable voltage area?” to measurable physical evidence and an owned correction.
Follow-up Question & Model Response
Follow-up probe: What would make you change your decision? Model response: “I would change it if the same controlled rerun shows that the region encloses enough area but cuts rows into unusable fragments or blocks supplies. I would use the named objects and reports to decide whether to iterate, waive, or return the issue.”
Practical Example
Symptom: The region encloses enough area but cuts rows into unusable fragments or blocks supplies. Corrective path: Reshape or move the region, rebuild affected rows/boundaries, and rerun multivoltage and floorplan checks.
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