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STA Mastery · All levels

Scenario: ECO Under Pressure

Critical path is reg2reg through congested region. PD proposes sizing; synthesis proposes VT swap; STA lead must choose minimal-risk ECO order.

Scenario

Critical path is reg2reg through congested region. PD proposes sizing; synthesis proposes VT swap; STA lead must choose minimal-risk ECO order.

diagram
OBSERVED METRIC
setup WNS -120ps with tapeout in 48 hours

45-MINUTE INTERVIEW FLOW
0-5: clarify corner/mode/view and path group
5-15: read critical path and constraints
15-25: classify constraint vs view vs real path
25-35: propose ECO order (setup/hold/SI)
35-45: state MMMC regression and signoff criteria

Common pitfalls

  • Fix setup without hold check

  • Skip SI re-run

  • No regression matrix

Scenario debrief

Score: corner/mode, path group, constraint check, ECO, regression.

diagram
constraints -> graph -> slack
diagram
WNS trend

Debrief prompts

  1. Which scenario failed first?

  2. Setup, hold, or both?

  3. What regression did you mandate?

Key takeaways

  • State corner, mode, view, and database tag with every slack claim.

  • Run setup and hold plus MMMC regression after every ECO.

Common pitfalls

  • Comparing STA runs with different SPEF or SDC tags.

  • Broad false_path to green-wash violations.

  • Setup-only ECO without hold check.

Practice this lesson