XSD: Restrict only one child element to have specific value

I have a XML which reads

<Options>
  <option1>Y</option1>
  <option2>N</option2>
  <option3>N</option3>
</Options>

I would like to ensure only one child element (of Options) has value Y so that above XML is valid but now the below one.

<Options>
  <option1>Y</option1>
  <option2>Y</option2>
  <option3>N</option3>
</Options>

I tried unique and referential integrity but couldn't work out.

Any help/idea much appreciated.

Thanks