LMK04031B

LMK04000 Family Low-Noise Clock Jitter Cleaner with Cascaded PLLs www.DataSheet4U.com July 24, 2009 LMK04000 Family Low-Noise Clock Jitter Cleaner with Cascaded PLLs 1.0 General Description The LMK04000 family of precision clock conditioners provides low-noise jitter cleaning, clock multiplication and distribution without the need for high-performance voltage controlled crystal oscillators (VCXO) module. Using a cascaded PLLatinum™ architecture combined with an external crystal and varactor diode, the LMK04000 family provides sub-200 femtosecond (fs) root mean square (RMS) jitter performance. The cascaded architecture consists of two high-performance phase-locked loops (PLL), a low-noise crystal oscillator circuit, and a high-performance voltage controlled oscillator (VCO). The first PLL (PLL1) provides a low-noise jitter cleaner function while the second PLL (PLL2) performs the clock generation. PLL1 can be configured to either work with an external VCXO module or use the integrated crystal oscillator with an external crystal and a varactor diode. When used with a very narrow loop bandwidth, PLL1 uses the superior close-in phase noise (offsets below 50 kHz) of the VCXO module or the crystal to clean the input clock. The output of PLL1 is used as the clean input reference to PLL2 where it locks the integrated VCO. The loop bandwidth of PLL2 can be optimized to clean the far-out phase noise (offsets above 50 kHz) where the integrated VCO outperforms the VCXO module or crys...