The LMX2571 is a low-power, high-performance, wideband
PLLatinum RF synthesizer that integrates a
delta-sigma fractional N PLL, multiple core voltage-controlled oscillator (VCO), programmable
output dividers and two output buffers. The VCO cores work up to 5.376 GHz resulting in continuous
output frequency range of 10 MHz to 1344 MHz.
This synthesizer can also be used with an external VCO. To that end, a dedicated 5-V
charge pump and an output divider are available for this configuration.
A unique programmable multiplier is also incorporated to help improve spurs, allowing the
system to use every channel even if it falls on an integer boundary.
The output has an integrated SPDT switch that can be used as a transmit/receive switch
in FDD radio application. Both outputs can also be turned on to provide 2 outputs at the same
The LMX2571 supports direct digital FSK modulation through programming or pins. Discrete
level FSK, pulse shaping FSK, and analog FM modulation are supported.
A new FastLock technique can be used allowing the user to step from one frequency to the
next in less than 1.5 ms even when an external VCO is used with a narrow band loop