regulator-output-exceeds-abs-max

Remedy ¶

Reprogram the regulator’s output to a voltage the downstream part is rated for, or move that part to a rail that already is. Both numbers come from vendor documents, so a design change settles this without needing a measurement.

What it checks ¶

A regulator’s datasheet output voltage against the absolute-maximum supply rating of a part it feeds. Both numbers come from vendor documents, and the finding cites both.

It is the first rule that compares a parameter on one part against a parameter on another part across the net joining them. Every datasheet rule before it read one spec against one rail.

For hardware engineers ¶

A regulator makes a rail. Everything on that rail is exposed to whatever the regulator puts out. If a 3.3V part sits on a rail a 5V regulator drives, the part is outside its absolute maximum from the moment power comes up, not marginal, not derated, outside the envelope the vendor will stand behind.

Absolute maximum is a stress limit, not an operating range. Exceeding it can destroy the part immediately, or damage it enough to fail months later in the field, and the second costs far more.

The check follows the supply one series element out, so a ferrite bead or a series resistor between the regulator and its load does not hide the connection. It does not follow further, and that is deliberate: unlike a surge, voltage does not fall off along a supply path, so a wider walk would make every part on the board look connected to every regulator and the rule would start pairing parts that share no supply at all.

Why it is not the same as supply-exceeds-abs-max ¶

supply-exceeds-abs-max asks a similar question, but it takes the rail voltage from the net name, where +5V means 5V. That is a naming convention, and conventions are silent or wrong exactly when you need them: a rail named VOUT_A carries no voltage in its name at all, and a rail named +5V that became 3.3V in a respin still reads as 5V.

This rule reads the number off the regulator’s own datasheet instead. Same question, evidence in place of a convention.

Neither replaces the other. A rail fed by something with no seeded datasheet, a connector or an unseeded module, still has only its name to go on, so the older rule keeps its job.

For software engineers ¶

A join over two projections that were previously read independently: the part’s supply-limit rows (SupplyAbsMaxLimits) and the driving part’s output rows (OutputVoltageLimits), connected by net membership within check.SupplyPathReachHops.

Where several rows are comparable the rule picks the extreme in the endangering direction: the highest output the source can present, against the lowest absolute maximum the load declares. An adjustable regulator endangers its load at the top of its range, and a part is endangered at its weakest rating, so any other pairing would under-report.

The finding carries both citations. That is why Finding.DatasheetProv is a slice: the review’s data-trust gate rates a finding by its weakest citation, and with a single slot a conclusion resting half on a low-confidence extraction would still have counted as a hard Fail.

When it stays silent ¶

• No seeded datasheet set. The rule reads the params tier, so check.Available gates it to not-applicable without --params. An unseeded design reads unevaluable, never clean.
• Either part unseeded. A regulator with no spec, or a load with no spec, yields no comparison, so skip, not pass.
• Under-specified rows. A parameter with text-only conditions or no max bound is skipped rather than coerced (docs/20). A number that cannot be compared honestly is not compared. A row printed in a prefixed unit (mV, kV) is not in that category since agni issue 148: the parameter layer reduces it to volts through its one conversion table, and only a unit that table does not recognize is skipped.

Fixing a finding ¶

Either the wrong regulator is feeding the rail, or the wrong part is on it. Check which of the two the design intended before changing a value: the rule reports the load as the subject because that is the part at risk, but the defect is as often the supply.