The NB4N441 is a precision clock synthesizer which generates a differential LVPECL clock output frequency from 12.5 MHz to 425 MHz. A Serial Peripheral Interface (SPI) is used to configure the device to produce one of sixteen popular standard protocol output frequencies from a single 27 MHz crystal reference. The NB4N441 also has the added feature of allowing application specific output frequencies from 12.5 MHz to 425 MHz using crystals within the range of 10 MHz to 28 MHz.