SNAS740B October 2017 – January 2019 LMX2572
PRODUCTION DATA.
The LMX2572 includes a fully integrated VCO. The VCO generates a frequency which varies with the tuning voltage from the loop filter. The entire VCO frequency range, 3.2 to 6.4 GHz, covers an octave that allows the channel divider to take care of frequencies below the lower bound.
To reduce the VCO tuning gain, thus improving the VCO phase noise performance, the VCO frequency range is divided into 6 different frequency bands. This creates the need for frequency calibration to determine the correct frequency band given in a desired output frequency. The VCO is also calibrated for amplitude to optimize phase noise. These calibration routines are activated any time that the R0 register is programmed with the FCAL_EN bit equals one. It is important that a valid OSCin signal must present before VCO calibration begins. This device will support a full sweep of the valid temperature range of 125°C (–40°C to 85°C) without having to re-calibrate the VCO. This is important for continuous operation of the synthesizer under the most extreme temperature variation.