Clock Jitter Cleaners Require No VCXO Modules

Emerging as the industry’s first family of clock jitter cleaners capable of providing low-noise clocks without external VCXO modules, the LMK04000 devices specify a sub-200-fs RMS jitter figure. The family consists of five clock conditioners: LMK04000B, LMK04001B, LMK04011B, LMK04031B, and the LMK04033B. The LMK04000B and LMK04001B offer 24.4 mW-ps per channel, while the LMK04031B and LMK04033B provide 25.4 mW-ps per channel and the LMK004011B delivers 37.4 mW-ps per channel. All devices employ the company’s cascaded PLLatinum architecture, which consists of two PLLs, a low-noise crystal oscillator circuit, a VCO, and low-noise dividers and drivers. The first PLL is configurable as an external crystal or a VCXO module to provide the jitter cleaning function while the second PLL relies on the VCO to perform clock generation. Other shared features include dual redundant inputs, five differential outputs, and an optional default-clock upon power-up. Sampling now in 48-pin LLPs with production ramping in the first quarter of 2009, price for all LMK04000 devices is $14.50 each/1,000. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959.