Electronicdesign 5664 Tvtab
Electronicdesign 5664 Tvtab
Electronicdesign 5664 Tvtab
Electronicdesign 5664 Tvtab
Electronicdesign 5664 Tvtab

PLL Synthesizer Offers High Output Frequency And Lowest Phase Noise

Jan. 24, 2013
New TI PLL synthesizer has a wide frequency range and very low phase noise.

The Texas Instruments LMX2581 phase-locked loop (PLL) frequency synthesizer integrates a voltage-controlled oscillator (VCO) that covers from 50 to 3760 MHz and offers perhaps the best phase-noise specification around. Normalized PLL phase noise is –229 dBc/Hz, and typical phase noise is –137 dBc/Hz at 1 MHz with a 2.5-GHz carrier. The normalized PLL 1/f noise is –120 dBc/Hz. The ultra-low phase noise is the result of design features such as its very high 200-MHz phase detector frequency.

The LMX2581 also offers the option of using integer or fractional PLL modes and optional dithering for spur reduction with the multi-order delta-sigma PLL. The integrated multicore VCO comes with its own tank circuit. The VCO may be bypassed in favor of an external VCO. A low-dropout regulator (LDO) is integrated to power the VCO.

Also included is a clock input divider and a programmable PLL output divider with a range of 1 (bypass) to 38. The noise floor is –155 dBc/Hz, and the in-band spur specification is –46 dBc. The chip has two 50-Ω differential outputs with programmable power levels from –4 to +10 dBm as well.

Typical applications include wireless infrastructure basestations, broadband wireless devices, test and measurement, and clock generation. The LMX2581 also suits a variety of radar and other defense and aerospace applications in addition to medical imaging. With the very low phase noise, the chip makes a superior precision local oscillator in an RF front end for excellent receiver sensitivity.

Texas Instruments’ LMX2581 is a fully integrated PLL frequency synthesizer for wireless and other communications applications. It covers from 50 to 3760 MHz and features a low normalized phase noise of –229 dBc/Hz.

The LMX2581 comes in a 32-pin, 5- by 5-mm, quad flat no-lead (QFN) package. Suggested price is $7 in 1000-unit quantities. An evaluation module is available for $175.

Texas Instruments         

www.ti.com/lmx2581ds-pr

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