SX1781IMLTRT

Clock Generators, PLLs, Frequency Synthesizers Overview

The SX1781IMLTRT is a high-performance integer-N frequency synthesizer featuring an integrated voltage-controlled oscillator (VCO) and loop filter. Designed for wireless communications, it operates within a 1200 to 1400 MHz output range with a minimum frequency step of 250 kHz. The device delivers -85 dBc/Hz phase noise at a 10 kHz offset and supports programmable output power up to +5 dBm when differential outputs are combined. It includes complementary RF outputs, an SPI interface for configuration, and a lock detector pin linked to a squelch function. The component functions on a 3.0 to 3.6 V supply and is housed in a 4 x 4 mm MLPQ16 package.

Clock Generators, PLLs, Frequency Synthesizers Feature Summary

• Integrated PLL with VCO tank and loop filter
• Output frequency range: 1200 to 1400 MHz
• Phase noise: -85 dBc/Hz @ 10 kHz offset
• Programmable output power up to +5 dBm
• Ultra-low power sleep mode (0.25 µA typical)

Clock Generators, PLLs, Frequency Synthesizers Applications

• Local Oscillator in superheterodyne transmitters
• Local Oscillator in superheterodyne receivers
• Wireless communication systems requiring low phase noise

Clock Generators, PLLs, Frequency Synthesizers Procurement Notes

Verify the MLCC capacitor values and inductor specifications for the balun network if utilizing the combined differential output configuration to achieve maximum power levels. Ensure the thermal pad is connected to ground for optimal heat dissipation during assembly. Confirm that the reference clock source meets the phase noise requirements specified for the target divider settings.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select this component when a fully integrated frequency synthesizer with minimal external passive components is required. The SX1781 is suitable for applications needing precise frequency steps down to 250 kHz and fast hopping times under 350 µs. Consider the single-ended (-1 dBm) versus combined differential (+5 dBm) output configurations based on system drive requirements and available matching networks.

Clock Generators, PLLs, Frequency Synthesizers Part Context

The SX1781 is part of Semtech's portfolio of advanced radio frequency integrated circuits designed for robust wireless connectivity. As an integer-N synthesizer, it simplifies board design by integrating the VCO and loop filter, reducing the bill of materials compared to discrete solutions. It targets markets demanding reliable local oscillation sources with strict phase noise performance constraints.

Clock Generators, PLLs, Frequency Synthesizers Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided documentation.