Active clock distribution: 3.1 GHz, multi-protocol, 3:5 fanout
The Texas Instruments LMK00304SQ/NOPB is a fanout buffer, multiplexer, and level translator in one device, designed for high-speed clock distribution in communications and data-center equipment. It accepts CML, HCSL, HSTL, LVDS, LVPECL, SSTL, or crystal inputs and outputs HCSL, LVCMOS, LVDS, or LVPECL levels, with a 3:1 input selector feeding a 1:5 fanout buffer. The 3.1 GHz maximum frequency covers PCIe Gen4/5, 100G Ethernet, and JESD204B clock trees.
A 3.1 GHz differential buffer handles the fundamental clock rates for 25 Gbps NRZ SerDes and 56 Gbps PAM-4 retimers without needing a separate divider or PLL. The fully differential signal path (input and output both differential-capable) preserves signal integrity across the fanout — important when the trace length from buffer to multiple ASICs or FPGAs exceeds a few inches.
The supply range is 3.15 V to 3.45 V, a tight ±4.5 % window around 3.3 V. This means the board's 3.3 V rail must be a regulated supply, not a raw bus.
The WQFN package with exposed pad keeps junction temperature under control even at maximum frequency and fanout.