AMS Interface · All levels
AMS Floorplan Keepouts: Comparison Matrix
Comparison Matrix for AMS Floorplan Keepouts.
Comparison matrix
Keepouts, guard strategy, and abutment policy trade area versus noise risk.
+------------------+----------------+----------------+----------------+
| Approach | Strength | Weakness | Best when |
+------------------+----------------+----------------+----------------+
| Conservative | robust | more overhead | new tapeout |
| Balanced | practical | needs rigor | mature flow |
| Aggressive | faster | high regressions | late stage |
| Architectural | durable | slow loop | recurring issue |
+------------------+----------------+----------------+----------------+When to choose each approach
Choose the smallest change that proves mechanism and preserves system margins.
Interview traps
Treating all AMS problems as analog-only
Skipping package and power evidence
Evidence comparison
AMS EVIDENCE MATRIX — AMS Floorplan Keepouts
+-------------------+------------------------+--------------------------+-------------------------+
| Evidence | Tells you | Does not prove | Next action |
+-------------------+------------------------+--------------------------+-------------------------+
| Waveform/log pair | sequence behavior | physical root cause | correlate with signoff |
| Signoff report | metric movement | contract correctness | audit assumptions |
| Floorplan view | physical proximity | dynamic mode behavior | run stress mode |
| Firmware trace | state progression | analog quality | combine with lab data |
| Dashboard summary | closure status | single-failure mechanism | inspect raw artifacts |
+-------------------+------------------------+--------------------------+-------------------------+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 signoffMetric 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
Keepout regions protect analog blocks from aggressor routing, switching clusters, and noisy clocks that inject disturbance through substrate and supplies.
Metric: keepout violation count, analog disturbance incidents, ECO rework