LMK5C33216's data sheet defines 1,000 MHz as the Max LVPECL output frequency. I guess it means the LMK5C33216 can generate LVPECL clocks of up to at least 1,000 MHz. The data sheet also adds, "(2) An output frequency over the fOUT max spec is possible, but the output swing may be less than the VOD min spec," as a note in the section 7.5 Electrical Characteristics. How high can the LMK5C33216 generate LVPECL output frequency practically? Do you have a performance plot of LVPECL fOUT vs VOD, for example?