Path Depth Sensitivity: Review Checklist

Review checklist

Review Checklist for Path Depth Sensitivity focuses on short-path hold margin, long-path setup margin, depth bucket WNS. The goal is to connect the observable symptom to timing mechanism, ownership, and regression risk.

• SDC revision and implemented clock/exception policy are named.

• Clock/reset and CDC assumptions are reviewed.

• Path groups, IO delays, and exception rationale are documented.

• MMMC scenario list maps back to signoff requirements.

• WNS/TNS artifact stored with corner/mode/view tags.

• Owners signed: STA owner, library owner.

Sign-off ownership

OWNERSHIP MAP — Path Depth Sensitivity

artifact              owner
----------------      -----------------
timing report       STA owner
SDC/constraint      library owner

Every WNS cluster needs a named owner before ECO.

STA deep dive

Variation policy is negotiated margin, not a tool checkbox.

Concept diagram

VARIATION STACK

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

Metric graph

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

Short paths see different variation pessimism than long paths; depth-aware models prevent both optimism and excess margin.

Metric: short-path hold margin, long-path setup margin, depth bucket WNS