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Clock jitter cleaners eliminate need for VCXO modules

Santa Clara, Calif. — National Semiconductor Corp. has claimed the industry's first family of clock jitter cleaners capable of providing ultra-low-noise clocks without external high-performance voltage-controlled crystal oscillator (VCXO) modules. Using a simple external crystal and cascaded PLLatinum architecture, the LMK04000 clock jitter cleaners provide sub-200 femtosecond (fs) root-mean-square (RMS) jitter to improve system performance and accuracy.

The LMK04000 family consists of five precision clock conditioners: the LMK04000B, LMK04001B, LMK04011B, LMK04031B and LMK04033B. These devices feature power-to-noise specifications that place them among National's PowerWise family of energy-efficient products. The LMK04000B and LMK04001B offer 24.4 mW-ps per channel, while the LMK04031B and LMK04033B are rated at 25.4 mW-ps per channel and the LMK004011B is 37.4 mW-ps per channel.

The LMK04000 devices provide clean clocks to analog-to-digital converters (ADCs), digital-to-analog converters (DACs) and other high-performance components used in wireless infrastructure, test and measurement, and medical ultrasound and imaging equipment. Wireless basestation applications include single-carrier and multi-carrier GSM (GSM), Long Term Evolution (LTE), Universal Mobile Telecommunications System (UMTS), Worldwide interoperability for Microwave Access (WiMAX) and Code Division Multiple Access (CDMA) networks.

The LMK04000 family uses National's cascaded PLLatinum architecture, which consists of two high-performance cascaded phase-locked loops (PLL), a low-noise crystal oscillator circuit, a high-performance integrated VCO as well as low-noise dividers and drivers. The first PLL can be configured to use a simple external crystal or a VCXO module to provide the jitter cleaning function while the second PLL uses the integrated VCO to perform low-noise clock generation.

The LMK04000 precision clock conditioners are supplied in 48-pin LLP packages.

Pricing: All devices are priced at $14.50 each in quantities of 1,000.
Availability: The LMK04011B, LMK04031B and LMK04033B are available now and the LMK04000B, LMK04001B are sampling now with production volumes expected in the first quarter of 2009.
Product information: LMK04000B, LMK04001B, LMK04011B, LMK04031B and LMK04033B, and National’s clock design tool

National Semiconductor , www.national.com

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