HTML5 Email validation pattern does not validate .edu.au, accepts even just edu.a

I'm supposed to be accepting only usyd.edu.au email addresses. The validation works, but it also works with usyd.edu.a emails. I want it to accept only when complete .au is entered. The pattern I have which works so far is:

input type="email", placeholder="Email" name="txtName" id="txtEmail" pattern="[a-z0-9._%+-]+@[usyd]+.[edu]+.[au]"/>