Wrapper/calibration choices trade observability, complexity, and residual error.
+------------------+----------------+----------------+----------------+
| Approach | Strength | Weakness | Best when |
+------------------+----------------+----------------+----------------+
| Tight aperture | accuracy | jitter sensitive | precision mode |
| Relaxed aperture | robustness | less precision | noisy conditions |
| Adaptive timing | balanced | complex FW | dynamic systems |
| Fixed coarse | simple | poor margin | low-cost flows |
+------------------+----------------+----------------+----------------+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 — Sample Timing Contract
+-------------------+------------------------+--------------------------+-------------------------+
| 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 |
+-------------------+------------------------+--------------------------+-------------------------+Wrapper and sampling contracts determine data trustworthiness.
CONVERTER DATA FLOW
sampling clock -> wrapper -> sync boundary -> system consumerINVALID SAMPLE BURSTS
time ---> _|¯¯|__|¯¯¯|____|¯|_sample validity ratio
calibration convergence
CDC audit
overflow/stale sample counters
Mode transition changed sample phase and invalidated wrapper framing assumptions.
Sample timing contract
Calibration hook behavior
Wrapper CDC integrity
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.
Sampling quality depends on clock phase relationships, aperture uncertainty, and synchronization boundaries between converter clocks and system clocks.
Metric: aperture budget compliance, sample alignment error, control-loop jitter
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