The B9940L is a low-voltage clock distribution buffer with the capability to select either a differential LVPECL- or an LVCMOS/LVTTL-compatible input clock. The two clock sources can be used to provide for a test clock as well as the primary system clock. All other control inputs are LVCMOS/LVTTL compatible. The eighteen outputs are 2.5V or 3.3V compatible and can drive two series-terminated 50 transmission lines. With this capability the B9940L has an effective fan-out of 1:36. Low output-to-output skews make the B9940L an ideal clock distribution buffer for nested clock trees in the most demanding of synchronous systems.