{
  "capability_id": "electrical.mosfet.tj",
  "tool_id": "mosfet-tj",
  "engine": "mosfet-tj",
  "calculation_version": "1.1.2",
  "generated_at": "2026-09-16T22:03:43.723Z",
  "engine_build": "2026-09-10",
  "test_count": 18,
  "passed": 18,
  "failed": 0,
  "tests_summary": {
    "golden": {
      "total": 3,
      "passed": 3
    },
    "boundary": {
      "total": 8,
      "passed": 8
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    "property": {
      "total": 5,
      "passed": 5
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    "formula_crosscheck": {
      "total": 2,
      "passed": 2
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  "engine_tested": true,
  "expert_reviewed": false,
  "internally_reviewed": true,
  "review_kind": "internal",
  "source_checked": true,
  "reviewed_by": "CalculatorX electrical review (EE-001)",
  "reviewer_role": "electrical-engineer",
  "last_reviewed": "2026-08-16",
  "expert_review": {
    "status": "not_applicable",
    "reviewer": null,
    "note": "Internal domain review completed; not a named external expert review.",
    "kind": "internal"
  },
  "internal_review": {
    "status": "approved",
    "reviewer": {
      "name": "CalculatorX electrical review (EE-001)",
      "role": "electrical-engineer"
    },
    "reviewed_at": "2026-08-16",
    "scope": [
      "formula",
      "input semantics",
      "assumptions",
      "limitations",
      "sources",
      "tests"
    ],
    "kind": "internal"
  },
  "page": "https://www.calculatorx.com/calc/electric/mosfet-tj",
  "api": "https://www.calculatorx.com/api/v1/calc/mosfet-tj",
  "schema_input": "https://www.calculatorx.com/schemas/electrical.mosfet.tj.input.json",
  "schema_output": "https://www.calculatorx.com/schemas/electrical.mosfet.tj.output.json",
  "assumptions": [
    "Steady-state lumped thermal resistance",
    "Rθ constant (not Zth(t))",
    "RθJA is an effective / application value for the user's thermal environment, not a JEDEC-board package constant",
    "JC+CA is a case/heatsink-dominant lumped single-path approximation; it does not model parallel heat-flow through PCB, leads, or package surfaces"
  ],
  "limitations": [
    "Steady-state only; not Zth or CFD",
    "Rth_JA is effective/application RθJA for the user's PCB and cooling environment, not a universal JEDEC package constant",
    "JC+CA is a case/heatsink-dominant lumped single-path approximation; it is not a universal equivalent of RθJA and ignores parallel PCB/package heat flow",
    "Rth_JA and Rth_JC or Rth_CA together is schema-invalid and CONFLICTING_INPUTS"
  ],
  "boundary_conditions": [
    "No Rth → MISSING_REQUIRED_INPUT",
    "Only one of JC/CA → NEEDS_TWO_INPUTS",
    "Rth_JA together with Rth_JC or Rth_CA → CONFLICTING_INPUTS",
    "P < 0 → VALUE_MUST_BE_NON_NEGATIVE",
    "Rth ≤ 0 → VALUE_MUST_BE_POSITIVE"
  ],
  "sources": [
    {
      "title": "Texas Instruments SPRA953D — Semiconductor and IC Package Thermal Metrics",
      "section": "RθJA, RθJC, and application dependence of junction-to-ambient metrics",
      "url": "https://www.ti.com/lit/pdf/spra953",
      "supports": "Tj ≈ Ta + P·RθJA as a thermal-metric estimate; RθJA is test-condition specific and is not a universal equivalent of RθJC+RθCA",
      "kind": "reference",
      "accessed": "2026-08-15"
    },
    {
      "title": "onsemi AND9016 — MOSFET Thermal Resistance",
      "section": "Junction-to-case / case-to-ambient thermal path",
      "url": "https://www.onsemi.com/download/application-notes/pdf/and9016-d.pdf",
      "supports": "Two-segment RθJC + RθCA for a case/heatsink-dominant path when package-bottom/PCB heat flow is neglected; RθCA lumps interface and heatsink-to-ambient",
      "kind": "reference",
      "accessed": "2026-08-15"
    },
    {
      "title": "JEDEC JESD51 series — Integrated circuit thermal measurement",
      "section": "Methodology for package thermal metrics",
      "supports": "Definition of junction-to-ambient and junction-to-case thermal metrics on specified test boards",
      "kind": "standard"
    }
  ],
  "methods": [],
  "fingerprint": "sha256:d029c5d041be798f8d2b71dbf5075d29c629ca574dba7a49e0019d550e6e8b0e",
  "tests": [
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      "id": "ja-105",
      "ok": true,
      "kind": "golden",
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        "Ta_C": 25,
        "P_W": 2,
        "Rth_JA": 40,
        "Tj_max_C": 150
      },
      "expect": {
        "Tj_C": 105,
        "dT_C": 80,
        "margin_C": 45,
        "path": "JA"
      },
      "expectWarning": null,
      "actual": {
        "Ta_C": 25,
        "P_W": 2,
        "Rth_C_per_W": 40,
        "path": "JA",
        "dT_C": 80,
        "Tj_C": 105,
        "Tj_max_C": 150,
        "margin_C": 45,
        "Rth_JA": 40,
        "Rth_JC": null,
        "Rth_CA": null
      },
      "tol": 1e-12
    },
    {
      "id": "jc-ca",
      "ok": true,
      "kind": "golden",
      "inputs": {
        "Ta_C": 25,
        "P_W": 1,
        "Rth_JC": 1.5,
        "Rth_CA": 8.5
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      "expect": {
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        "dT_C": 10,
        "path": "JC+CA"
      },
      "expectWarning": null,
      "actual": {
        "Ta_C": 25,
        "P_W": 1,
        "Rth_C_per_W": 10,
        "path": "JC+CA",
        "dT_C": 10,
        "Tj_C": 35,
        "Tj_max_C": null,
        "margin_C": null,
        "Rth_JA": null,
        "Rth_JC": 1.5,
        "Rth_CA": 8.5
      },
      "tol": 1e-12
    },
    {
      "id": "margin-neg",
      "ok": true,
      "kind": "golden",
      "inputs": {
        "Ta_C": 50,
        "P_W": 4,
        "Rth_JA": 30,
        "Tj_max_C": 150
      },
      "expect": {
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        "dT_C": 120,
        "margin_C": -20
      },
      "expectWarning": null,
      "actual": {
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        "P_W": 4,
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        "path": "JA",
        "dT_C": 120,
        "Tj_C": 170,
        "Tj_max_C": 150,
        "margin_C": -20,
        "Rth_JA": 30,
        "Rth_JC": null,
        "Rth_CA": null
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      "tol": 1e-12
    },
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      "ok": true,
      "kind": "formula_crosscheck",
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        "P_W": 1,
        "Rth_JA": 50
      },
      "expect": {
        "Tj_C": 75,
        "dT_C": 50,
        "path": "JA"
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      "expectWarning": null,
      "actual": {
        "Ta_C": 25,
        "P_W": 1,
        "Rth_C_per_W": 50,
        "path": "JA",
        "dT_C": 50,
        "Tj_C": 75,
        "Tj_max_C": null,
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        "Rth_JA": 50,
        "Rth_JC": null,
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      "tol": 1e-12
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      "id": "xref-onsemi-jc-ca",
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        "P_W": 2,
        "Rth_JC": 1,
        "Rth_CA": 4
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        "dT_C": 10,
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        "P_W": 2,
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        "Rth_CA": 4
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      "tol": 1e-12
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      "ok": true,
      "kind": "boundary",
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        "P_W": 0,
        "Rth_JA": 40
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        "dT_C": 0,
        "path": "JA"
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        "dT_C": 0,
        "Tj_C": 25,
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        "Rth_JA": 40,
        "Rth_JC": null,
        "Rth_CA": null
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      "tol": 1e-12
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      "ok": true,
      "kind": "boundary",
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        "Rth_JA": 40
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      "expectError": "VALUE_MUST_BE_NON_NEGATIVE",
      "code": "VALUE_MUST_BE_NON_NEGATIVE",
      "error": "P_W must be ≥ 0"
    },
    {
      "id": "boundary-neg-rth",
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      "kind": "boundary",
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        "P_W": 1,
        "Rth_JA": -5
      },
      "expectError": "VALUE_MUST_BE_POSITIVE",
      "code": "VALUE_MUST_BE_POSITIVE",
      "error": "Rth_JA must be greater than zero"
    },
    {
      "id": "boundary-only-jc",
      "ok": true,
      "kind": "boundary",
      "inputs": {
        "Ta_C": 25,
        "P_W": 1,
        "Rth_JC": 1.5
      },
      "expectError": "NEEDS_TWO_INPUTS",
      "code": "NEEDS_TWO_INPUTS",
      "error": "Rth_JC and Rth_CA must both be provided"
    },
    {
      "id": "boundary-only-ca",
      "ok": true,
      "kind": "boundary",
      "inputs": {
        "Ta_C": 25,
        "P_W": 1,
        "Rth_CA": 8.5
      },
      "expectError": "NEEDS_TWO_INPUTS",
      "code": "NEEDS_TWO_INPUTS",
      "error": "Rth_JC and Rth_CA must both be provided"
    },
    {
      "id": "boundary-missing-rth",
      "ok": true,
      "kind": "boundary",
      "inputs": {
        "Ta_C": 25,
        "P_W": 1
      },
      "expectError": "MISSING_REQUIRED_INPUT",
      "code": "MISSING_REQUIRED_INPUT",
      "error": "thermal resistance required"
    },
    {
      "id": "boundary-conflict",
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        "P_W": 2,
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        "Rth_JC": 1.5,
        "Rth_CA": 8.5
      },
      "expectError": "CONFLICTING_INPUTS",
      "code": "CONFLICTING_INPUTS",
      "error": "Provide Rth_JA, or Rth_JC+Rth_CA, not both paths"
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    {
      "id": "boundary-at-max",
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        "Rth_JA": 62.5,
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        "Rth_JA": 62.5,
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