Boundary strategy choices trade robustness, area, and schedule 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 |
+------------------+----------------+----------------+----------------+Choose the smallest change that proves mechanism and preserves system margins.
Treating all AMS problems as analog-only
Skipping package and power evidence
AMS EVIDENCE MATRIX — Noise Coupling Basics
+-------------------+------------------------+--------------------------+-------------------------+
| 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 |
+-------------------+------------------------+--------------------------+-------------------------+Boundary assumptions must be explicit, versioned, and testable.
BOUNDARY CONTRACT FLOW
analog intent -> boundary implementation -> digital wrapper -> signed reviewBOUNDARY RISK MIX
missing boundary cells ███████
stale handoff assumptions ██████
silent mode changes ████boundary-cell coverage
isolation/ESD review
handoff contract checklist
integration waiver log
Noise bursts traced to missing isolation clamp on one low-power transition mode.
Validate boundary-cell insertion
Diff handoff assumptions
Reproduce with tagged mode sequence
Ask: what boundary condition proves this topic is actually closed?
State boundary, mode, and evidence tag with every claim.
Always align analog, digital, and physical owners before signoff decisions.
Fixing averages while tails still fail.
Skipping package/supply evidence in jitter or SerDes issues.
Shipping with waivers that lack owner and expiration criteria.
Supply, substrate, and interconnect coupling inject deterministic and random noise at boundaries; layout proximity and return-path quality control the coupling magnitude.
Metric: victim noise peak, substrate coupling estimate, interface error bursts
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