cap-voltage

Remedy ¶

Fit a capacitor rated above the worst rail it touches, with the derating the design’s own rules call for. On ceramics, allow for the capacitance lost under applied DC bias as well.

What it means ¶

A component is classed as a capacitor and joined by MPN to a seeded datasheet spec. The spec carries a rated voltage, as a VDC/WV/VR-family symbol or a “Rated Voltage” row. The component sits on a rail, and the rail’s declared voltage times the derate factor (1.25) exceeds that rating.

Why engineers want it ¶

This rule turns the classic review checklist item (“is every cap rated for its rail, with margin?”) into a check whose limit is the vendor’s number with provenance, not a rule-of-thumb constant in code. The finding cites the datasheet page/table so the margin is verifiable. That follows the datasheet layer’s whole posture (architecture/datasheet-layer.md).

What it skips rather than guesses ¶

Every untrusted input is a skip, never a guess: no MPN / unseeded MPN / no seeded corpus; no machine-comparable rated-voltage row (architecture/datasheet-layer.md, “Comparison semantics”); units other than “V”; a rail with neither a max_voltage attribute nor a name-derived nominal. The worst (highest) known rail among the cap’s nets governs. Because a skip and a pass look the same to the spec, the rule reports violations only and states no considered set.

Query structure ¶

Spec-authored (architecture/rules-and-checks.md, “A rule is a value”). The join and float compare live in the cap_voltage_detail SpecFunc. It returns the violation sentence or “”, so the rule body is still an AST and the derived Reads carry the param join as named relations.

select C in components where class(C) == capacitor
  and cap_voltage_detail(C) != ""    // Vrated < worst_rail_V x 1.25, seeded and comparable

Reads: param.cap_rated_voltage, net.max_voltage, component.mpn, component.class, on_net. Tier R.