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Derate Policy & Approval: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Derate Policy & Approval.

Step-by-step analysis walkthrough

Use when you own Derate Policy & Approval in a timing war room.

  1. Open signoff scenario list — note worst WNS corner.

  2. report_timing -max/-min on failing group.

  3. Trace launch and capture clocks on critical path.

  4. Check exceptions and generated clocks on path.

  5. Break down cell vs net delay.

  6. Compare implementation vs signoff view if delta suspicious.

  7. Assign owner: RTL, synth, PD, CTS, SI.

  8. Propose ECO with hold/SI check plan.

  9. Run regression matrix.

  10. Update closure dashboard and memo.

Artifacts to collect

  • derate approval memo, signoff policy PDF, before/after WNS comparison

  • SDC file

  • SPEF tag

  • MMMC scenario list

  • ECO ticket

Decision memo template

diagram
STA DECISION MEMO — Derate Policy & Approval
corner/mode:
WNS/TNS:
hypothesis:
ECO:
regression:
owners: STA lead, PD director, foundry signoff

Reference visuals

Derate approval flow

diagram
DERATE CHANGE REQUEST
  -> STA lead review
  -> PD director sign
  -> foundry policy check
  -> re-run full MMMC matrix
  -> archive before/after WNS

STA deep dive

Variation policy is negotiated margin, not a tool checkbox.

Concept diagram

diagram
VARIATION STACK

nominal delay + OCV/AOCV/POCV margin = signoff delay

Metric graph

diagram
DERATE IMPACT ON WNS

OCV only     WNS -120ps
AOCV         WNS -45ps
POCV         WNS -60ps (policy dependent)

Reports and artifacts

  • derate table

  • AOCV depth report

  • POCV sigma

  • hold/setup split

Mini case study

Switched to AOCV without re-baselining hold — short paths failed min analysis.

Debug branches

  • Short paths for hold

  • Policy approval for derate changes

Senior review question

Ask: what corner/mode/view proves this topic is closed or failing?

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.

Principal STA review addendum

Derating policy is a contractual margin between implementation and signoff; changes need documented approval and regression.

Metric: approved derate set, waiver count, signoff pessimism budget

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