Mixed-Signal Physical Verification: Interview Drills

Interview drills

Interview Drills for Mixed-Signal Physical Verification focuses on AMS PV closure rate, signoff waiver count, rerun turnaround. The goal is to connect observed symptom to boundary mechanism, ownership, and signoff risk.

PROMPT
You see AMS PV closure rate, signoff waiver count, rerun turnaround on Mixed-Signal Physical Verification. Walk through root cause and fix.

STRONG ANSWER
1. Names boundary and mode.
2. Explains Mixed-signal PV combines digital and analog rule decks, LVS partition assumptions, and waiver discipline to achieve manufacturable signoff.
3. Requests PV signoff dashboard, LVS mismatch summary, waiver approvals.
4. Proposes one bounded fix and full regression.

WEAK ANSWER
Jumps to random tuning or tool commands without proving mechanism and ownership.

Diagram to draw on whiteboard

Mixed-signal PV closure

DRC + LVS + ERC + analog-specific checks
          -> waiver review
          -> AMS release gate

Root-cause tree to narrate

ROOT-CAUSE TREE — Mixed-Signal Physical Verification

AMS PV closure rate, signoff waiver count, rerun turnaround regressed
        |
same silicon / run tags?
   /            \
 no              yes
 |                |
env mismatch    boundary contract or
tag mismatch    true physical issue
 /   \             |
clk   reset      isolate first failing
map   sequence   boundary transition

AMS deep dive

Physical proximity and boundary rules are functional constraints in AMS SoCs.

Concept diagram

INTEGRATION FLOW

floorplan keepouts -> guard strategy -> abutment policy -> PV signoff

Metric graph

INTEGRATION ESCAPES

layout boundary issues ███████
waiver drift           ████

Reports and artifacts

• keepout violations

• guard-ring checks

• abutment DRC

• mixed-signal PV dashboard

Mini case study

Late macro move violated quiet-zone assumptions and caused intermittent converter noise excursions.

Debug branches

• Review macro adjacency

• Re-check guard assumptions

• Re-run PV with correct deck variant

Senior review question

Ask: what boundary condition proves this topic is actually closed?

Key takeaways

• State boundary, mode, and evidence tag with every claim.

• Always align analog, digital, and physical owners before signoff decisions.

Common pitfalls

• Fixing averages while tails still fail.

• Skipping package/supply evidence in jitter or SerDes issues.

• Shipping with waivers that lack owner and expiration criteria.

Principal AMS review addendum

Mixed-signal PV combines digital and analog rule decks, LVS partition assumptions, and waiver discipline to achieve manufacturable signoff.

Metric: AMS PV closure rate, signoff waiver count, rerun turnaround