Source: https://guthlabs.ai/docs/instruments/crystal-oscillator-load-capacitance-calculator/mechanism/

instrument mechanism / verified-clean

# Crystal Oscillator Load Capacitance Calculator mechanism

The inspectable method record for Crystal Oscillator Load Capacitance Calculator, kept separate from implementation and qualification.

Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**

## Model scope

The core formulas are standard under the stated lumped-parasitic and symmetric-capacitor assumptions. Verdict is NEEDS_REVIEW because the specification leaves units, the exact meaning of Cstray, validity constraints, topology assumptions, and honest limitations unspecified. The honest label should state that results are nominal estimates for a symmetric Pierce-style load network and do not guarantee the crystal's operating frequency.

- CL=(C1C2)/(C1+C2)+Cstray is the standard nominal load-capacitance formula when Cstray is the total effective parasitic capacitance and all capacitances use the same units.

- For the symmetric case C1=C2=C, the result C=2(CL−Cstray) is algebraically exact, not merely approximate; approximation only enters when selecting real standard capacitor values and accounting for tolerances and parasitics.

- The specification does not define whether Cstray includes the oscillator IC pin capacitances, PCB/layout capacitance, probe capacitance, or other parasitics.

- The specification does not state the required validity constraint CL>Cstray for positive external capacitors, nor does it explain how to handle CL≤Cstray.

- The two-input specification only supports the symmetric C1=C2 solution; unequal C1 and C2 values cannot be uniquely determined from CL and Cstray alone.

## Units and conventions

- CL, Cstray, C1, and C2 must be expressed in identical capacitance units; the examples use pF unless explicitly marked otherwise.

- Cstray is treated as one lumped capacitance in parallel with the crystal's effective load network.

- The crystal's rated CL is assumed to use the same load-capacitance convention as the formula.

- The reported values are nominal capacitor values before capacitor tolerance, voltage coefficient, PCB parasitics, and oscillator input-pin capacitance are included.

## Inspectable vector

One of 4 source-bound review vectors:

````
{
  "inputs": {
    "crystal_rated_CL": "18 pF",
    "estimated_stray_capacitance": "3 pF",
    "assumption": "C1=C2"
  },
  "expected_outputs": {
    "C1": "30 pF",
    "C2": "30 pF"
  },
  "working": "C1=C2=2(CL−Cstray)=2(18 pF−3 pF)=2(15 pF)=30 pF. Verification: CL=(30×30)/(30+30)+3=(900/60)+3=15+3=18 pF."
}
````

## Failure boundary

**BREAK_CLAIMED** · SELF_FLAGGED

The symmetric formula returns a zero-valued capacitor at the exact CL=Cstray boundary, which should be rejected for practical component selection, and very large valid-looking numeric input overflows JavaScript arithmetic to Infinity instead of producing a finite result or a clear validation error.

## Other records

[01**Overview**](<https://guthlabs.ai/docs/instruments/crystal-oscillator-load-capacitance-calculator/>)[03**Implementation**](<https://guthlabs.ai/docs/instruments/crystal-oscillator-load-capacitance-calculator/implementation/>)[04**Qualification**](<https://guthlabs.ai/docs/instruments/crystal-oscillator-load-capacitance-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-tranche5/tranche5-results.json`

- `BOUNDARY_HAZARD_CATALOG.json`