AMS Floorplan Keepouts

What this topic teaches

AMS Floorplan Keepouts converts analog-digital assumptions into a measurable engineering contract. Keepout regions protect analog blocks from aggressor routing, switching clusters, and noisy clocks that inject disturbance through substrate and supplies. The hard part is proving which boundary broke first, under which mode, and with which evidence.

The senior-engineer question

When keepout violation count, analog disturbance incidents, ECO rework moves, can you isolate the first failing boundary, identify owner, and define the smallest reversible change that proves root cause?

AMS CLOSURE FLOW — AMS Floorplan Keepouts

spec + handoff assumptions
        |
        v
boundary implementation (wrapper/cells/reset)
        |
        v
physical context (floorplan/power/package)
        |
        v
metrics + artifacts (jitter/BER/noise/validity)
        |
        v
root-cause classification -> bounded fix -> regression

Debug rule: always name mode, boundary, evidence tag, and owner.

Picture the boundary behavior

Start every study session by drawing the contract before opening logs or reports. The diagrams below are what to reproduce on whiteboard.

Floorplan keepout model

analog macro [keepout + quiet routes + dedicated supplies]
surrounding digital switching must respect noise boundaries.

Boundary sequence

AMS BOUNDARY SEQUENCE — AMS Floorplan Keepouts

analog macro -> wrapper / boundary cell -> synchronizer or sampler -> digital consumer
      |                 |                         |                     |
  analog assumptions    legal voltage/state       clock/reset contract   protocol/data validity

metric under watch: keepout violation count, analog disturbance incidents, ECO rework

Who owns which layer

AMS OWNERSHIP LAYERS — AMS Floorplan Keepouts

layer                owns                                failure mode
------------------   ----------------------------------  --------------------------
spec contract         clocks/resets/interfaces            hidden assumption drift
wrapper logic         synchronizers/framing/flags         silent data corruption
physical integration  floorplan/isolation/power           coupled noise and droop
signoff governance    waivers/checklists/dashboard        release with blind spots
closure               debug order + regression            fix regresses another mode

Evidence to collect

• Primary metric: keepout violation count, analog disturbance incidents, ECO rework.

• Primary artifact: floorplan keepout map, congestion overlay, integration signoff note.

• Owners to bring into review: floorplan owner, analog lead, PD lead.

• One tagged reproduction and one reduced reproducer.

• Cross-check from at least two evidence planes: functional and physical/signoff.

Ownership map

OWNERSHIP MAP — AMS Floorplan Keepouts

artifact                  owner
----------------------    -----------------------------
integration artifact    floorplan owner
implementation artifact analog lead
signoff artifact        PD lead

Every boundary issue needs a named owner before fixes start.

Subpages in this topic

Each topic includes mechanism, contract I/O, reports, debug, worked example, pitfalls, interview, checklist, theory, design-space, extended case study, walkthrough, comparison matrix, software view, and silicon PPA impact.

Key takeaways

• Carry boundary and mode context with every metric.

• Prove mechanism with tagged evidence before changing silicon-facing logic.

• Close with explicit owner-aligned regression criteria.

Common pitfalls

• Assuming lock/ready/valid means healthy behavior.

• Ignoring package and power contributors in jitter/SerDes issues.

• Waivers without expiry, owner, or mitigation plan.

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.