Section goal

Fault models, ATPG constraints, pattern quality criteria, and coverage closure strategy.

How to study this section

1. Start with the topic hub for architecture and ownership context.

2. Use mechanism and reports pages to map assumptions to metrics.

3. Use debug and worked examples for real closure patterns.

4. Finish with checklist and silicon impact before release decisions.

Topics

1. fault-models/ - Fault Models

2. atpg-constraints/ - ATPG Constraints

3. pattern-signoff/ - Pattern Signoff

4. coverage-closure/ - Coverage Closure

Related topics

• DFT course hub

DFT deep dive

ATPG quality comes from fault model choice plus legal constraints, not raw pattern volume alone.

Concept diagram

ATPG FLOW

fault model -> constraints -> generation -> simulation -> coverage closure -> signoff

Metric graph

COVERAGE GAP

target coverage
  ^
  |      o before closure
  |          o after fixes
  +---------------------> iteration

Reports and artifacts

• fault model coverage

• untestable class report

• constraint legality errors

• pattern signoff memo

Mini case study

Transition coverage stalled due to clock constraints mismatch; updated at-speed capture definitions recovered target.

Debug branches

• Classify untestable faults

• Diff ATPG constraints each run

• Pair coverage with pattern budget

Senior review question

Ask: what evidence proves this DFT decision is safe for production?