ADF4251BCP

Overview

The ADF4251BCP is a dual fractional-N/integer-N frequency synthesizer manufactured by Analog Devices Inc. It integrates two independent synthesizers: an RF section supporting up to 3.0 GHz with fractional-N division and an IF section supporting up to 1.2 GHz with integer-N division. Both sections utilize low-noise digital phase frequency detectors, precision charge pumps, and programmable reference dividers. The device operates on a single 2.7 V to 3.3 V supply, features separate VP pins for extended tuning voltage up to 5.5 V, and includes a 3-wire serial interface for register control. It is housed in a 24-lead CP package.

Feature Summary

• Dual synthesizer architecture: RF (Fractional-N, 3.0 GHz max) and IF (Integer-N, 1.2 GHz max).
• Programmable dual modulus prescalers: RF supports 4/5 or 8/9; IF supports 8/9, 16/17, 32/33, or 64/65.
• Separate VP1 and VP2 power supplies allow extended tuning voltage up to 5.5 V for external VCOs.
• Integrated digital lock detect and hardware/software power-down modes.

Applications

• Base stations for mobile radio (GSM, PCS, DCS, CDMA, WCDMA)
• Wireless handsets (GSM, PCS, DCS, CDMA, WCDMA, PHS)
• Wireless LANs
• Communications test equipment
• CATV equipment

Procurement Notes

Verify the specific ordering suffix against the manufacturer's guide. The base model ADF4251BCP uses a CP-24 lead frame chip scale package. Suffixes such as -REEL or -REEL7 indicate reel packaging options. Confirm the temperature range is industrial (-40°C to +85°C) for the B version. Ensure ESD precautions are observed during handling due to the high-performance RF nature of the component.

Selection Notes

Select this component when a dual local oscillator solution is required for upconversion and downconversion paths within a single package. The RF section is suitable for frequencies up to 3.0 GHz using fractional-N synthesis, while the IF section handles integer-N synthesis up to 1.2 GHz. Ensure the external VCO tuning voltage requirements are met by utilizing the separate VP1 and VP2 pins, which support voltages up to 5.5 V. Verify that the input sensitivity and phase detector frequencies align with the system design constraints.

Part Context

The ADF4251BCP belongs to the ADF4251 series of dual frequency synthesizers from Analog Devices. It is designed to replace discrete PLL solutions in wireless infrastructure and portable devices. The device simplifies board layout by integrating both RF and IF loops into one LFCSP package, reducing component count and potential noise sources associated with multiple chips.

Replacement Considerations

Public confirmed substitute part numbers are not available in the provided documentation. Consult Analog Devices for current cross-reference data if alternative sourcing is required.