I have a text box. When user types in it, it does a query and shows the result (alternative to drop down with AJAX)

The problem is, if user types a bit faster it doesn't do the enquiry.

I am doing
HTML Code:
<input type="text" name="id_originator_label" value="{$POST.id_originator_label}" class="text" id="id_originator_label"   onkeyup="serial_onchange(this,getRefById('id_originator'), 'serial_results3', '{$ajax_js_dir}/persons/persons_onchange.php','',0,',');" />
		<div id="id_originator_maindiv" style="position:absolute;top:115px;right:25px;width:200px;height:300px;border:none;display:none;">
			<iframe id="id_originator_iframe" frameborder="0" style="position:absolute;top:0px;left:0px;width:200px;height:300px;"></iframe>
			<div id="serial_results3" class="ajaxdropdown" />
			<input type="text" name="id_originator" value="{$POST.id_originator}" class="text" id="id_originator" style="display:none;" />
Some things I manually changed in the JS script to fit my needs (fields like id_originator_search or id_originator_iframe have special purposes.

Again, it works fine if i type in slowly.