Voltage Regulator (Linear) Resistor/Output Calculator mechanism

Model scope

The core nominal LM317-style voltage formula is correct, but the specification is incomplete and ambiguous because Iadj is undeclared, the inverse calculations are unspecified, and the promised minimum-load-current check has no defined threshold or method. The honest label is empty; it should state that this is an ideal nominal calculator and not a complete regulator design or compliance check.

• The stated formula is standard for an ideal LM317-style adjustable regulator: Vout = Vref(1 + R2/R1) + Iadj·R2, assuming R1 is from OUT to ADJ and R2 is from ADJ to ground.
• The specification claims a min load current check, but provides no minimum-load-current threshold, regulator model, or formula for that check; its result cannot be defined unambiguously.
• Iadj appears in the formula but is missing from the declared inputs. The calculator must define whether Iadj is required, optional with a default, or assumed to be zero.
• The inverse formulas for calculating a missing resistor are not stated. For R2: R2 = (Vout - Vref)/(Vref/R1 + Iadj). For R1: R1 = Vref·R2/(Vout - Vref - Iadj·R2).
• The formula is an ideal nominal calculation and does not account for Vref tolerance, Iadj tolerance, resistor tolerance, dropout voltage, thermal limits, current limits, or regulator-specific behavior.

Units and conventions

• Vref and Vout are in volts (V).
• R1 and R2 are in ohms (Ω), and both resistors must use the same resistance unit before arithmetic.
• Iadj is in amperes (A); for example, 50 µA must be entered as 0.000050 A.
• The resistor orientation is R1 from regulator output to adjust/reference node and R2 from that node to ground, as used by the LM317 convention.
• The formula computes nominal output voltage only; regulator input voltage must exceed Vout by the device's required dropout margin, but that condition is not represented by the formula.

Inspectable vector

One of 4 source-bound review vectors:

{
  "inputs": {
    "Vref_V": 1.25,
    "R1_ohm": 240,
    "R2_ohm": 720,
    "Iadj_A": 0.00005
  },
  "expected_outputs": {
    "Vout_V": 5.036
  },
  "working": "R2/R1 = 720/240 = 3. 1 + R2/R1 = 4. Vref·(1 + R2/R1) = 1.25·4 = 5.000 V. Iadj·R2 = 0.00005·720 = 0.036 V. Vout = 5.000 + 0.036 = 5.036 V."
}

Failure boundary

• Division by zero occurs when calculating R2 if Vref/R1 + Iadj = 0; this can occur with invalid R1, zero Vref, or negative/unphysical Iadj.
• Division by zero occurs when calculating R1 if Vout - Vref - Iadj·R2 = 0.
• Calculated resistor values can be zero or negative; the calculator must reject nonpositive resistor values for a physical design, except that R2 = 0 is mathematically valid as a boundary test case.
• R1 = 0 is invalid because the forward formula contains R2/R1.
• Inputs must reject negative resistance, negative Vref where inappropriate, and inconsistent target values that require a negative resistor.
• The result may violate the regulator's minimum-load-current requirement, maximum output-current rating, power dissipation, or dropout-voltage requirement.
• Using milliamps or microamps as though they were amperes causes a factor-of-1000 or factor-of-1000000 error in the Iadj term.
• A fixed minimum-load threshold cannot be reported honestly without specifying the regulator part number or an explicit threshold.

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json