The LMX2471 is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL. The device is fabricated using National Semiconductor’s advanced BiC-MOS process. With delta-sigma architecture, fractional spur compensation is achieved with noise shaping capability of the delta-sigma modulator and the inherent low pass filtering of the PLL loop filter. Fractional spurs at lower frequencies are pushed to higher frequencies outside the loop bandwidth. Unlike analog compensation, the digital feedback techniques used in the LMX2471 are highly resistant to changes in temperature and variations in wafer processing. With delta-sigma architecture, the ability to push close in spur and phase noise energy to higher frequencies is a direct function of the modulator order. The higher the order, the more this energy can be spread to higher frequencies. The LMX2471 has a programmable modulator up to order four, which allows the designer to select the optimum modulator order to fit the phase noise, spur, and lock time requirements of the system. Programming is fast and simple. Serial data is transferred into the LMX2471 via a three line MICROWIRE interface (Data, Clock, Load Enable). Nominal supply voltage is 2.5 V. The LMX2471 features a typical current consumption of 5.6 mA at 2.5 V. The LMX2471 is available in a 24 lead 3.5 X 4.5 X 0.6 mm package. Features n Low power, high performance delta-sigma fractional-N PLLn Auxiliary integer-N PLLn Fabricated using National Semiconductor’s advanced BiC-MOS processn Noise shaping capability of the delta-sigma modulatorn Inherent low pass filtering of the PLL loop filtern Energy can be spread to higher frequenciesn Fast and simple programming
The LMX2471 is a low power, high performance delta-sigma fractional-N PLL with an auxiliary integer-N PLL, fabricated using National Semiconductor's advanced BiCMOS process. It features a programmable modulator up to order four, allowing designers to select the optimum modulator order to fit phase noise, spur, and lock time requirements. Programming is fast and simple via a three-line MICROWIRE interface.
| Operating Frequency (RF) | 500 to 3600 MHz |
|---|---|
| Operating Frequency (IF) | 250 to 1700 MHz |
| Phase Detector Frequency (RF) | 50 MHz |
| Phase Detector Frequency (IF) | 10 MHz |
| Crystal Reference Frequency | up to 110 MHz |
| Operating Temperature | -40 to +85 C |
| Typical Current Consumption | 5.6 mA |
| Package Type | 24 lead 3.5 X 4.5 X 0.6 mm |
The device supports a crystal reference frequency up to 110 MHz.
The LMX2471 features a typical current consumption of 5.6 mA at 2.5 V.
Programming is done via a three line MICROWIRE interface consisting of Data, Clock, and Load Enable.