Datasheets

Give the tool a part's real limits as data, and it checks every design that uses the part against them.

Most rules only need your design. A few can also check it against a part’s real limits from its datasheet, once you give the tool those limits as data. This page turns that on.

Transcribe a part’s limits once (the Absolute Maximum Ratings, the operating range) into a small file, and the tool compares every design that uses the part against them. See “datasheets as checkable data” in Concepts.

Load a parameter set

A parameter set is a directory of small text files, one per part, each holding that part’s specs. Point check at it with --params:

$ agni check regulator.fires.kicad_sch --params ./params/ --rule supply-exceeds-abs-max
findings by rule:
  supply-exceeds-abs-max 1

first 1:
  [error] supply-exceeds-abs-max: U1 (power-input pin 1 on rail "+24V": nominal 24V exceeds absolute-maximum VIN 20V — datasheet "SNOS412Q - FEBRUARY 2000 - REVISED JANUARY 2023" page 4, "7.1 Absolute Maximum Ratings" (hand, confidence 1))

1 finding(s) total
1 subject(s) considered by 1 rule(s), 1 not considered (--verdicts for the detail)

Read that finding: the design drives a +24V rail into U1 pin 1, whose datasheet caps VIN at 20V absolute maximum. The message carries a dual citation, your design side (the rail and pin) and the datasheet side (document, page, and the exact table). You can open the datasheet to page 4 and confirm it.

For the tool to match a datasheet to a placed part, the design has to name the part: an MPN on the BOM line, or the MPN/Manufacturer properties a schematic symbol carries.

What the tool will and will not auto-compare

The tool is deliberately conservative about when it compares a number automatically.

  • A limit stated as a plain number the tool can act on (VIN abs-max = 20V) is machine-comparable and can fire a finding.
  • A limit that only holds under a text condition the tool cannot evaluate (“20V at 25°C ambient, derate above”) is shown to a human rather than auto-compared, because applying that derating is a judgement rather than a comparison. The tool will not pretend to a certainty the datasheet did not give it.
  • A part whose spec is missing the fields a rule needs is under-specified and is skipped, not guessed.

This is why an empty or partial parameter set makes datasheet rules go quiet rather than wrong: no data means the rule had nothing to compare, the same tier logic as everywhere else.

The last line of the run above is where that shows up. One subject was considered and one was not considered, which is the rule declining rather than passing it. A findings report on its own cannot tell you which of the two happened, so read that line alongside the count.

Confidence and provenance

Each spec value records where it came from and how much to trust it. A limit typed in by a person reads as the highest confidence. A value extracted automatically from a PDF carries a lower confidence and its own page/table citation. The finding message surfaces this (the (hand, confidence 1) tail above), so a reviewer can weigh a machine-extracted limit differently from a hand-verified one.

Where the specs come from

You author a parameter set by transcribing the limits you care about (facts from a datasheet are not copyrightable, so cite the document revision and page). There is also a pipeline that extracts specs from a PDF automatically, which is a separate tool covered in the developer docs. Either way the result is the same small per-part files this page loads.

Where to go next