Phase noise frequency synthesizer features integrated VCO that outputs 50 to 3760-MHz

January 21, 2013 // By Paul Buckley
Texas Instruments Incorporated has introduced a wideband frequency synthesizer with integrated voltage-controlled oscillator (VCO) that claims to deliver the industry’s lowest phase noise.

The device’s combination of ultra-low noise phase-locked loop (PLL) and industry’s highest phase detector frequency outperforms the competition in both phase noise and spurs. The LMX2581 combines the capability to drive highest system performance along with the flexibility of a wideband frequency synthesizer that outputs 50 to 3760 MHz. The device allows designers to use one frequency synthesizer to support a variety of demanding applications in wireless infrastructure, radar, medical imaging, defense and aerospace, and test and measurement.

In addition, the LMX2581 improves total link power efficiency and communication channel capacity when combined with the following high-speed analog signal chain devices from TI: LMK04828 or LMK04800 clock jitter cleaner; AD42JB69 dual-channel, 16-bit, 250-MSPS analog-to-digital converter (ADC) with JESD204B serial interface or ADC16DV160 dual-channel, 16-bit, 160-MSPS ADC; DAC34SH84 quad-channel, 16-bit, 1.5-GSPS digital-to-analog converter (DAC), and the TRF3705 300-MHz to 4-GHz quadrature modulator.

The LMX2581 has a phase detector frequency of 200 MHz and ultra-low PLL normalized phase noise of -229 dBc/Hz , which provides a precision local oscillator to an RF front end for better receiver sensitivity.

Integrated VCOs allow the device to output frequencies from 50 MHz to 3760 MHz, eliminating the multiple VCO/PLL combinations typically required to support a broad range of applications. The LMX2581 also gives designers the option to bypass its internal multi-core VCO in favor of an external VCO.

The delta-sigma PLLatinum PLL engine with 200-MHz phase detector frequency boosts spurious performance.

The ultra-low noise, wideband frequency synthesizer integrates a delta-sigma fractional-N PLL; a multi-core VCO with tank circuit; optional frequency divider; two differential RF output buffers that can deliver 10 dBm single-ended on each side; and several low-noise, high precision low dropout regulators (LDOs).

The LMX2581EVAL evaluation module can be purchased for $175. The synthesizer’s companion Clock Design Tool and CodeLoader software help speed system design by aiding engineers with product selection, loop filter design and simulation of timing solutions. Both of these tools and