You can use so called "Event Delegates".
See this little Demo:
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta charset="utf-8">
<script src="https://openui5.hana.ondemand.com/resources/sap-ui-core.js"
id="sap-ui-bootstrap"
data-sap-ui-libs="sap.m,sap.ui.layout,sap.f"
data-sap-ui-theme='sap_fiori_3'></script>
<script>
var btn = new sap.m.Link({
text:'Hello World',
press: function(evt){
var pop = new sap.m.Popover({
title: "MyPopOver",
placement: "Bottom",
contentWidth: "200px",
content: [new sap.m.Text({text: "My Text"})]
})
pop.addEventDelegate({
onmouseout: function() {
pop.close()
}
}, this);
pop.openBy(evt.getSource());
}
});
btn.placeAt('content');
</script>
</head>
<body id="content" class="sapUiBody">
</body>
</html>
Beware, this one already closes, if you touch a text inside the popup, but you'll get the generell idea.