Silicon PPA and closure impact

Clocking quality and supply behavior shift real converter validity windows.

Area drivers

• Boundary cells and guards add area

• Routing keepouts can increase utilization pressure

Power drivers

• Added margins cost power

• Jitter/noise mitigation can increase static and dynamic budgets

Timing impact

• Jitter and uncertainty consume timing

• IR/noise shifts practical timing margin

PD consequences

• Keepouts and strap topology alter congestion and CTS paths

• Package constraints affect lane routing

Verification burden

• Need aligned AMS + digital + package evidence

• Waiver discipline is mandatory

PPA — Sample Timing Contract
area/power/timing/closure-time tradeoff

PPA takeaways

• Mixed-signal fixes are multi-objective

• Signoff is cross-team, not single-report

Design option PPA snapshot

BEFORE / AFTER — Sample Timing Contract

health score
  ^
  |                     --- target
  |         o regressed
  |               o before fix
  |                    o after bounded fix
  +--------------------------------------> debug iteration

Prove signal quality, timing margin, and integration safety together.

AMS deep dive

Wrapper and sampling contracts determine data trustworthiness.

Concept diagram

CONVERTER DATA FLOW

sampling clock -> wrapper -> sync boundary -> system consumer

Metric graph

INVALID SAMPLE BURSTS

time --->  _|¯¯|__|¯¯¯|____|¯|_

Reports and artifacts

• sample validity ratio

• calibration convergence

• CDC audit

• overflow/stale sample counters

Mini case study

Mode transition changed sample phase and invalidated wrapper framing assumptions.

Debug branches

• Sample timing contract

• Calibration hook behavior

• Wrapper CDC integrity

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

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