What this PCIe clock buffer does on the board
The Renesas 9ZX21901BKLF is a PLL-based zero-delay buffer that takes two differential clock inputs and fans them out to nineteen HCSL outputs, all running at up to 400 MHz. It is built for Intel-platform timing trees — specifically Intel QPI and PCI Express (PCIe) reference clocks — where you need one clean source to feed multiple endpoints without skew. The 2:19 ratio means you can route separate clock trees for the root complex, switches, and downstream slots from a single device. Full differential path on both sides keeps signal integrity intact across a server motherboard.
Supply rail and temperature — where it fits
The part runs on a 3.135 V to 3.465 V supply. The operating temperature range is 0°C to 70°C.
Lifecycle and sourcing
The 9ZX21901BKLF is listed as Active with ROHS3 compliance. For a wider-temperature variant, the 9ZXL0851EKKLF (1:8 fan-out) and 9ZXL1231EKILF (1:12 fan-out) are functional peers rated -40°C to 85°C.