How can i make it so my website is displayed 1080px on all devices except anything less than a width of 480px.

Im using the viewport meta tag, which works fine for all devices:
Code:
<meta name="viewport" content="width=1080">
However i would like to be able to override the meta tag only on devices less than 480px.
Code:
@media (max-width: 480px){
//my mobile site css
}
Ive searched the internet and found this code, but im not sure how to use it.
Code:
@viewport{ width:1080px;}
@-ms-viewport{width:1080px;}
Any ideas?