The LMX2531 is a low-power, high-performance frequency synthesizer system which includes a fully integrated delta-sigma PLL and VCO with fully integrated tank circuit. The third and fourth poles are also integrated and adjustable. Ultra-low noise and high-precision LDOs are integrated for the PLL and VCO, which yield higher supply-noise immunity and more consistent performance. When combined with a high-quality reference oscillator, the LMX2531 device generates very stable, low-noise local-oscillator signals for up and down conversion in wireless communication devices. The LMX2531 device is a monolithic integrated circuit, fabricated in an advanced BiCMOS process. Several different versions of this product accommodate different frequency bands.