Documentation sections

Power Supply Ripple Filter

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

Slug power-supply-ripple-filter. Calculate LC filter attenuation, resonant frequency, and output ripple voltage. Design power supply EMC filters for ripple rejection.

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 power-supply-ripple-filter
Name	Unit	Range	Default	Description
inputRipplenumber	mV	at least 0.001	100	Input Ripple Voltage
frequencynumber	kHz	at least 0.001	100	Ripple Frequency
inductancenumber	μH	0.001 … 100000	10	Inductor Value
capacitancenumber	μF	0.001 … 100000	10	Capacitor Value
eSeriesnumber	none	0 … 96	0	Rounds every part to the nearest value in the series; the response and the export are the rounded design's.One of: 0 Ideal values · 12 E12 (10%) · 24 E24 (5%) · 48 E48 (2%) · 96 E96 (1%)

Outputs

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

Outputs of power-supply-ripple-filter
Field	Unit	Description
resonantFreq	kHz	Filter Resonant Frequency
attenuation	dB	Attenuation
outputRippleheadline	mV	Output Ripple

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": "power-supply-ripple-filter",
    "inputs": {
      "inputRipple": 100,
      "frequency": 100,
      "inductance": 10,
      "capacitance": 10,
      "eSeries": 0
    }
  }'

import rftools

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

result = client.calculate("power-supply-ripple-filter", {
    "inputRipple": 100,
    "frequency": 100,
    "inductance": 10,
    "capacitance": 10,
    "eSeries": 0,
})
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": "power-supply-ripple-filter",
    "inputs": {
      "inputRipple": 100,
      "frequency": 100,
      "inductance": 10,
      "capacitance": 10,
      "eSeries": 0
    }
  }),
});
console.log(response.status, await response.json());

package main

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

func main() {
	body := []byte(`{
	  "slug": "power-supply-ripple-filter",
	  "inputs": {
	    "inputRipple": 100,
	    "frequency": 100,
	    "inductance": 10,
	    "capacitance": 10,
	    "eSeries": 0
	  }
	}`)
	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": "power-supply-ripple-filter",
  "values": {
    "resonantFreq": 15.915494309189537,
    "attenuation": -31.927194734324598,
    "outputRipple": 2.5330295910584457
  },
  "warnings": [],
  "errors": [],
  "provenance": {
    "method": "calculator:power-supply-ripple-filter",
    "version": "api@3f2c1a9b04de",
    "formulaRef": null,
    "assumptions": [],
    "validRange": {
      "status": "inside",
      "bounds": {
        "inputRipple": {
          "min": 0.001,
          "max": null,
          "unit": "mV"
        },
        "frequency": {
          "min": 0.001,
          "max": null,
          "unit": "kHz"
        },
        "inductance": {
          "min": 0.001,
          "max": 100000,
          "unit": "μH"
        },
        "capacitance": {
          "min": 0.001,
          "max": 100000,
          "unit": "μF"
        },
        "eSeries": {
          "min": 0,
          "max": 96,
          "unit": ""
        }
      },
      "outside": [],
      "model": null
    },
    "computedAt": "2026-09-24T14:05:11.003Z",
    "inputs": {
      "inputRipple": 100,
      "frequency": 100,
      "inductance": 10,
      "capacitance": 10,
      "eSeries": 0
    },
    "seed": null,
    "elapsedSeconds": 0.003
  }
}

{
  "detail": [
    {
      "type": "float_parsing",
      "loc": [
        "body",
        "inputs",
        "inputRipple"
      ],
      "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 pagePower Supply Ripple Filter, at these values