The NBC12439 and NBC12439A are general purpose, PLL based synthesized clock sources. The VCO will operate over a frequency range of 400 MHz to 800 MHz. The VCO frequency is sent to the N-output divider, where it can be configured to provide division ratios of 1, 2, 4 or 8. The VCO and output frequency can be programmed using the parallel or serial interfaces to the configuration logic. Output frequency steps of 16 MHz, 8 MHz, 4 MHz, or 2 MHz can be achieved using a 16 MHz crystal, depending on the output divider settings. The PLL loop filter is fully integrated and does not require any external components.