What the 400 MHz and 1:15 ratio mean for your clock tree
The 9ZX21501BKLF: This is a PLL-based differential clock buffer with HCSL outputs, rated for a maximum frequency of 400 MHz — the ceiling for PCI Express Gen3/4 and Intel QPI reference clocks. The 1:15 input-to-output ratio fans out a single differential clock to fifteen HCSL loads, which covers a full server blade or a dense PCIe switch fabric without needing a second buffer stage.
Package and rework — 64-VFQFN with exposed pad
Surface-mount only — no through-hole variant exists. The exposed pad requires a hot-air rework profile consistent with lead-free solder; the pad also serves as the primary ground return for the PLL core.