{HEAD ~ A clock buffer} in a semiconductor memory device includes two kinds of interface circuits, {TAIL ~ i.e., an LVTTL interface} and an SSTL interface 
{ HEAD ~ A clock buffer } in a semiconductor memory device includes two kinds of interface circuits , { TAIL ~ i.e. , an LVTTL interface } and an SSTL interface
HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH