# Switching Converters

This constraint ensures tight ground return loops for input and output paths, minimizing EMI and voltage ripple. 

This is a special case that applies only to switching converters with a specific configuration, consisting of two or more external capacitors (input and output capacitors) and an external output inductor. Other configurations are not supported and are generally unnecessary for achieving good results. 

During compilation, this constraint requires the three passive components to be positioned as closely as possible to the converter package.

### Automatic Detection

Certain switching converters will be detected automatically:

* The reference designator for the switching converter must begin with `U`
* The switching converter output connects to an inductor with a reference designator that begins with `L` 

Quilter can handle regulator configurations with multiple input or output capacitors, but will somewhat arbitrarily select one for the purposes of constraining switching coverter placement.

{% hint style="info" %}
**Regulator Not Detected**\
If your converter/regulator is not detected, this is not a cause for concern, and the compilation process will work fine
{% endhint %}

### Constraint Details

<figure><img src="/files/rM37Ke0tLsrgszbwsUCy" alt=""><figcaption></figcaption></figure>

Set up switching regulator constraints in the "Switching Converters" section of Circuit Comprehension.&#x20;

To add a switching converter constraint, enter the following information:

* Switching converter (reference designator, must begin with `U`)
* Output inductor (reference designator, must begin with `L`)
* (optional) Input capacitor&#x20;
* (optional) Output capacitor

If Quilter did not automatically detect your Switching Converter, you can add it manually by pressing the `Add` button.&#x20;

### Physics Rule Checks

The PRCs that validate this constraint after compile are:

**Pin Distance** calculates the Euclidian distance between the closest edges of two pins.

**Layer Switch Count** finds the number of times there is a layer switch in a trace path between two pins

**Trace Path Length** calculates the trace length between two pins of interest.

**Ground Plane Overlap** determines if the ground plane below net traces overlaps at all relevant points.


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