Source: https://guthlabs.ai/docs/instruments/crystal-oscillator-load-capacitance-calculator/
instrument / verified-clean
# Crystal Oscillator Load Capacitance Calculator
The current ledger marks this instrument verified clean within the source-bound verification corpus.
Status: **VERIFIED_CLEAN**Lifecycle: **verified-clean**
## Inspectable records
[01**Overview**Purpose and lifecycle]()[02**Mechanism**Method and assumptions]()[03**Implementation**Binding and validation]()[04**Qualification**Evidence and errata]()
## Ledger state
The current ledger marks this instrument verified clean within the source-bound verification corpus.
**Area**: Electrical & Electronics Engineering — Circuits, Power Systems, Electronics Lab
**Tranche**: tranche-5
**Evidence ID**: t5-183
**Ledger rows**: 1
No ledger note is attached.
## Review findings
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.
### Formula and scope findings
- 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.
### Unit assumptions
- 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.
## Boundary hardening
**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.
## Errata and corrections
No applied erratum is attached to this unique-name record.
## Inspectable example
4 review vectors are recorded. One source-bound sample is shown below.
````
{
"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."
}
````
## Related workflows
No source-defined multi-instrument workflow membership is recorded.
## Sources and evidence
These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.
- `VERIFIED_LEDGER.json · VERIFIED_CLEAN`
- `evidence-tranche5/tranche5-results.json`
- `BOUNDARY_HAZARD_CATALOG.json`