Source: https://guthlabs.ai/docs/instruments/heat-sink-thermal-resistance-calculator/implementation/

instrument implementation / implementation-contract

# Heat Sink Thermal Resistance Calculator implementation

A source-bound implementation contract for Heat Sink Thermal Resistance Calculator; deployment and executable qualification remain separate.

Status: **VERIFIED_CLEAN**Lifecycle: **implementation-contract**

## Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

**Record owner**: Guth Instruments

**Lifecycle**: verified-clean

**Evidence ID**: t4-290

**Effect**: Computation or source lookup only

## Input and validation requirements

The specified output includes margin to Tj(max), but the specification provides no Tj(max) input or fixed value, making that output undefined. Additionally, sufficiently large finite JavaScript inputs overflow Tj to Infinity.

## Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

## Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

````
{
  "inputs": {
    "Ta": 25,
    "Ta_unit": "°C",
    "P": 10,
    "thetaJC": 1.2,
    "thetaCS": 0.3,
    "thetaSA": 4.5,
    "theta_unit": "°C/W",
    "Tj_max": 125,
    "Tj_max_unit": "°C"
  },
  "expected_outputs": {
    "Tj": 85,
    "Tj_unit": "°C",
    "margin_to_Tj_max": 40,
    "margin_unit": "°C"
  },
  "working": "θtotal = 1.2 + 0.3 + 4.5 = 6.0 °C/W. Temperature rise = 10 W × 6.0 °C/W = 60 °C. Tj = 25 °C + 60 °C = 85 °C. Margin = 125 °C − 85 °C = 40 °C."
}
````

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/heat-sink-thermal-resistance-calculator/>)[02**Mechanism**](<https://guthlabs.ai/docs/instruments/heat-sink-thermal-resistance-calculator/mechanism/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/heat-sink-thermal-resistance-calculator/qualification/>)

## 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`