DenseChip

AMS Interface · All levels

IR at Analog Islands: Step-by-Step Walkthrough

Step-by-Step Walkthrough for IR at Analog Islands.

Step-by-step analysis walkthrough

Use this when you own IR at Analog Islands during an AMS war room.

  1. Capture failing mode and environmental condition.

  2. Pull synchronized waveform, logs, and report artifacts.

  3. Mark first boundary where legal behavior diverges.

  4. Audit reset/clock/power sequence assumptions.

  5. Check physical coupling contributors (floorplan/power/package) where relevant.

  6. Assign single-thread ownership for the first fix.

  7. Propose bounded change and define success criterion.

  8. Run scenario and safety regressions.

  9. Document findings in closure memo.

  10. Update signoff dashboard and waiver state.

Artifacts to collect

  • IR map around islands, dynamic droop trace, power-grid review memo

  • handoff contract

  • firmware/config tag

  • physical signoff snapshot

  • decision memo

Decision memo template

diagram
AMS DECISION MEMO — IR at Analog Islands
mode/condition:
metric:
hypothesis:
fix:
regression:
owners: power integrity owner, PD owner, AMS integrator

Reference visuals

IR around analog islands

diagram
PG straps -> local droop map -> analog bias shift -> jitter/SNR impact

AMS deep dive

AMS signoff is a combined noise, IR, timing, and package decision.

Concept diagram

diagram
BOUNDARY SIGNOFF

noise + IR + package + timing -> release decision

Metric graph

diagram
RISK DASHBOARD

open blockers █████
waivers       ███

Reports and artifacts

  • supply ripple spectrum

  • IR around analog islands

  • package PI summary

  • release dashboard

Mini case study

IR hotspot at analog island caused jitter spikes only under burst traffic.

Debug branches

  • Correlate droop and jitter

  • Check package return path

  • Validate mode-specific activity profile

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

IR drop localized near analog islands distorts bias points and clock quality; strap topology and domain partitioning define resilience under burst load.

Metric: local droop at analog islands, guardband consumption, reset excursions

Practice this lesson