LTC6946IUFD-4

Clock Generators, PLLs, Frequency Synthesizers Overview

The LTC6946IUFD-4 is an ultralow noise and spurious integer-N synthesizer with a fully integrated voltage-controlled oscillator (VCO), manufactured by Analog Devices Inc. It operates within a VCO frequency range of 4.20 GHz to 6.39 GHz. The device features a programmable output divider ranging from 1 to 6, enabling RF output frequencies from 0.700 GHz to 6.39 GHz. Key electrical specifications include a reference input frequency up to 250 MHz, a charge pump current adjustable from 250 µA to 11.2 mA, and supply voltages of 3.15 V to 3.45 V for digital/RF sections and 4.75 V to 5.25 V for the VCO and charge pump. It is housed in a 28-lead QFN package.

Clock Generators, PLLs, Frequency Synthesizers Feature Summary

• Integrated low-noise VCO with no external components required; internally calibrated.
• Programmable output divider (O_DIV) with integer settings from 1 to 6.
• Adjustable charge pump current ranging from 250 µA to 11.2 mA with selectable high and low voltage clamps.
• SPI-compatible serial port control with configurable status output.

Clock Generators, PLLs, Frequency Synthesizers Applications

• Low Noise Integer-N PLL systems
• Wireless Base Stations (LTE, WiMAX, W-CDMA, PCS)
• Broadband Wireless Access
• Military and Secure Radio
• Test and Measurement

Clock Generators, PLLs, Frequency Synthesizers Procurement Notes

Verify component authenticity through authorized distributors or direct manufacturer channels. Confirm the specific -4 suffix indicates the 4.20 GHz to 6.39 GHz VCO frequency band. Ensure the ordering suffix matches the required packaging format, such as #PBF for tube or #TRPBF for tape and reel. Check for RoHS compliance documentation corresponding to the lead-free finish.

Clock Generators, PLLs, Frequency Synthesizers Selection Notes

Select the LTC6946IUFD-4 when the target VCO frequency falls between 4.20 GHz and 6.39 GHz. Consider the output divider setting to achieve the desired final RF frequency range. Evaluate the charge pump current requirements against loop filter design constraints. Ensure the system supports the required 5V supply for the VCO and charge pump circuits alongside the 3.3V logic supplies.

Clock Generators, PLLs, Frequency Synthesizers Part Context

The LTC6946 series comprises four variants differentiated by their internal VCO frequency coverage. The -1 variant covers 2.24–3.74 GHz, the -2 covers 3.08–4.91 GHz, the -3 covers 3.84–5.79 GHz, and the -4 covers 4.20–6.39 GHz. All variants share identical pinouts, control interfaces, and peripheral circuitry requirements, differing only in the factory-calibrated VCO tuning range.

Clock Generators, PLLs, Frequency Synthesizers Replacement Considerations

Publicly confirmed substitute part numbers are not available in the provided source material. Designers requiring alternative frequency bands should consider other members of the LTC6946 family (-1, -2, or -3) if the application frequency allows. Cross-referencing with other manufacturers' integer-N synthesizers requires careful evaluation of phase noise and supply voltage compatibility.