If all you want is an XSD so that the XML you gave conforms to it, you'd be much better off by crafting it yourself rather than using a tool.
No one knows better than you the particularities of the schema, such as which valid values are there (for instance, is the <maxlength> element required? are true and false the only valid values for <required>?).
If you really want to use a tool (I'd only advice using it if you haven't designed the XML and really can't get the real XSD - or if you designed it, double check the generated XSD), you could try Trang. It can infer an XSD Schema from a number of example XML's.
You'll have to take into account that the XSD a tool can infer you might be incomplete or inaccurate if XML samples aren't representative enough.
java -jar trang.jar sampleXML.xml inferredXSD.xsd
You can find a usage example of Trang here.