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Synthesizer provides
Posted: 09 Jul 2009 ?? ?Print Version ?Bookmark and Share

Keywords:frequency synthesizer? noise? PowerWise?

LMX2541

National Semiconductor Corp. has announced what it claims is the industry's lowest-noise, fully integrated frequency synthesizer, the PowerWise LMX2541. The LMX2541 provides less than 2mrad rms noise at 2.1GHz and 3.5mrad rms noise at 3.5GHz, outperforming the nearest competitor by 10dB in both in-band PLL noise and spurious performance.

The LMX2541 is well-suited for local oscillator applications in next-generation base station radio transceivers such as LTE, WiMAX and multi-standard radios. When paired with the LMK04000 clock jitter cleaner, the LMX2541 significantly improves system EVM, resulting in enhanced receiver sensitivity and transmitter spectral purity.

The LMX2541 is offered in a family of six devices covering a wide range of frequencies from 31.6MHz to 4,000MHz. The LMX2541 improves total link power efficiency and communication channel capacity when combined with National's ADC16V130 high-speed ADC, LMH6517 digital variable gain amplifier (DVGA) and LMK04000 clock jitter cleaner.

The LMX2541 features a fully integrated, ultralow-noise delta-sigma fractional-N PLL, voltage-controlled oscillator (VCO), divider and output driver. The PLL offers a normalized noise floor of -225dBc/Hz and can be operated with up to 104MHz of phase-detector rate (comparison frequency) in both integer and fractional modes. It also can be configured to work with an external VCO. The LMX2541 offers advanced features such as programmable output power, digital frequency-shift-keying (FSK) modulation, FastLock mode with cycle-slip reduction and a low-noise, integrated-input crystal oscillator circuit.

In addition, the LMX2541 integrates the necessary LDO regulators and output-driver matching network to provide higher supply noise immunity and more consistent performance, while reducing the number of external components. The LMX2541's supply voltage range is 3.15V to 3.45V, and device programming is facilitated using a three-wire MICROWIRE bus interface that can operate down to 1.8V.

The LMX2541 builds on the foundation of National's PLLatinum architecture and packaging technology. National fabricates the LMX2541 on SiGe BiCMOS-8 process technology in its South Portland, Maine, facility.

The LMX2541 is sampling now in a 6mm x 6mm, 36-pin LLP package, with production volumes expected in Q4 09. The LMX2541 is priced at $9.50 each in 1,000-unit quantities.





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