Documentation sections

ESD Clamp Diode Selection

POSThttps://rftools.io/api/py/v1/calculate

Slug esd-clamp-selection. Calculate ESD clamp diode peak current, power dissipation, and clamping ratio. Verify TVS protection for IEC 61000-4-2 compliance.

Inputs

Send every one of these in inputs, in the units shown. Most are required: a call without one is refused (400) and costs nothing; one the calculator can do without takes the default shown. An input outside its range is still computed and flagged in the provenance.

Inputs of esd-clamp-selection
Name	Unit	Range	Default	Description
esdVoltagenumber	V	at least 100	4000	IEC 61000-4-2 Level 4: ±8 kV contact
clampVoltagenumber	V	at least 1	15	TVS clamping voltage at peak current from datasheet
lineImpedancenumber	Ω	at least 0.1	330	Series resistance in ESD discharge path
standardnumber	none	0 … 1	0	IEC 61000-4-2 contact discharge (preferred) or air discharge (where contact is not possible)One of: 0 IEC 61000-4-2 contact · 1 IEC 61000-4-2 air
testLevelnumber	none	1 … 4	4	The IEC 61000-4-2 test level the product must pass; the product standard sets itOne of: 1 Level 1 · 2 Level 2 · 3 Level 3 · 4 Level 4

Outputs

Returned in values, by key. A value that is unbounded or undefined is null.

Outputs of esd-clamp-selection
Field	Unit	Description
peakCurrentheadline	A	Peak Clamp Current
clampPower	W	Peak Power Dissipation
voltageMargin	V	Voltage Margin
clampingRatio	none	Clamping Ratio
testVoltage	V	The IEC 61000-4-2 test voltage of the chosen discharge method and level: the least strike voltage the clamp must be checked at
limitPercent	%	The test voltage as a percentage of the strike voltage checked; above 100 % the check is below the test level

Calling it

Calculate: one call, the request and response in full, and its errors.
Batch: this calculator with others, or a sweep, in one request.
Solve for a target: the value of one input that brings an output to a target.

curl -X POST https://rftools.io/api/py/v1/calculate \
  -H "X-API-Key: $RFTOOLS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "slug": "esd-clamp-selection",
    "inputs": {
      "esdVoltage": 4000,
      "clampVoltage": 15,
      "lineImpedance": 330,
      "standard": 0,
      "testLevel": 4
    }
  }'

import rftools

client = rftools.Client()  # reads RFTOOLS_API_KEY, or the key `rftools login` saved

result = client.calculate("esd-clamp-selection", {
    "esdVoltage": 4000,
    "clampVoltage": 15,
    "lineImpedance": 330,
    "standard": 0,
    "testLevel": 4,
})
print(result.values)
print(result.warnings, result.provenance.formula_ref)

const response = await fetch("https://rftools.io/api/py/v1/calculate", {
  method: "POST",
  headers: {
    "X-API-Key": process.env.RFTOOLS_API_KEY,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    "slug": "esd-clamp-selection",
    "inputs": {
      "esdVoltage": 4000,
      "clampVoltage": 15,
      "lineImpedance": 330,
      "standard": 0,
      "testLevel": 4
    }
  }),
});
console.log(response.status, await response.json());

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	body := []byte(`{
	  "slug": "esd-clamp-selection",
	  "inputs": {
	    "esdVoltage": 4000,
	    "clampVoltage": 15,
	    "lineImpedance": 330,
	    "standard": 0,
	    "testLevel": 4
	  }
	}`)
	req, err := http.NewRequest("POST", "https://rftools.io/api/py/v1/calculate", bytes.NewReader(body))
	if err != nil {
		panic(err)
	}
	req.Header.Set("X-API-Key", os.Getenv("RFTOOLS_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

application/json

{
  "slug": "esd-clamp-selection",
  "values": {
    "peakCurrent": 12.075757575757576,
    "clampPower": 181.13636363636365,
    "voltageMargin": 3985,
    "clampingRatio": 0.00375,
    "testVoltage": 8000,
    "limitPercent": 200
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:esd-clamp-selection",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "esdVoltage": {
          "min": 100,
          "max": null,
          "unit": "V"
        },
        "clampVoltage": {
          "min": 1,
          "max": null,
          "unit": "V"
        },
        "lineImpedance": {
          "min": 0.1,
          "max": null,
          "unit": "Ω"
        },
        "standard": {
          "min": 0,
          "max": 1,
          "unit": ""
        },
        "testLevel": {
          "min": 1,
          "max": 4,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "esdVoltage": 4000,
      "clampVoltage": 15,
      "lineImpedance": 330,
      "standard": 0,
      "testLevel": 4
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "esdVoltage"
      ],
      "msg": "Input should be a valid number, unable to parse string as a number",
      "input": "abc"
    }
  ]
}

An input sent as text. Nothing was counted.

{
  "detail": "More than 120 requests in 60 seconds from this address.",
  "errorKind": "rate_limited",
  "limit": 120,
  "windowSeconds": 60,
  "upgradeUrl": "https://rftools.io/pricing/"
}

Too many requests in a minute, with Retry-After.

Same inputs on the calculator pageESD Clamp Diode Selection, at these values