DenseChip

AMS Interface · All levels

Analog Supply Noise: Step-by-Step Walkthrough

Step-by-Step Walkthrough for Analog Supply Noise.

Step-by-step analysis walkthrough

Use this when you own Analog Supply Noise 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

  • supply noise simulation, ripple spectrum, decap strategy report

  • handoff contract

  • firmware/config tag

  • physical signoff snapshot

  • decision memo

Decision memo template

diagram
AMS DECISION MEMO — Analog Supply Noise
mode/condition:
metric:
hypothesis:
fix:
regression:
owners: PI owner, analog lead, package owner

Reference visuals

Supply noise path

diagram
digital burst current -> shared impedance -> analog ripple/spurs -> performance loss

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

Switching current bursts from digital domains couple through shared impedance and package parasitics, modulating analog supply quality and phase noise.

Metric: supply ripple, spur coupling, analog performance degradation

Practice this lesson