ADF4251 Datasheet | Analog Devices

FEATURES 3.0 GHz Fractional-N/1.2 GHz Integer-N 2.7 V to 3.3 V Power Supply Separate V P Allows Extended Tuning Voltage to 5 V Programmable Dual Modulus Prescaler RF: 4/5, 8/9 IF: 8/9, 16/17, 32/33, 64/65 Programmable Charge Pump Currents 3-Wire Serial Interface Digital Lock Detect Power-Down Mode Programmable Modulus on Fractional-N Synthesizer Trade-Off Noise versus Spurious Performance Software and Hardware Power-Down APPLICATIONS Base Stations for Mobile Radio (GSM, PCS, DCS, CDMA, WCDMA) Wireless Handsets (GSM, PCS, DCS, CDMA, WCDMA, PHS) Wireless LANs munications Test Equipment CATV Equipment GENERAL DESCRIPTION The ADF4251 is a dual fractional-N/integer-N frequency synthesizer that can be used to implement local oscillators (LO) in the upconversion and downconversion sections of wireless receivers and transmitters. Both the RF and IF synthesizers consist of a low noise digital PFD (phase frequency detector), a precision charge pump, and a programmable reference divider. The RF synthesizer has a ⌺-⌬ based fractional interpolator that allows programmable fractional-N division. The IF synthesizer has programmable integer-N counters. A plete PLL (phase-locked loop) can be implemented if the synthesizer is used with an external loop filter and VCO (voltage controlled oscillator). Control of all the on-chip registers is via a simple 3-wire interface. The devices operate with a power supply ranging from 2.7 V to 3.3 V and can be powered down when not in use. FUNCTIONAL BLOCK DIAGRAM VDD1 VDD2 VDD3 DVDD VP1 VP2 RSET CE REFERENCE ؋2 DOUBLER 4-BIT R COUNTER REFIN PHASE FREQUENCY DETECTOR CHARGE PUMP CPRF MUXOUT OUTPUT MUX LOCK DETECT FRACTIONAL N RF DIVIDER RFINA RFINB CLK DATA LE 24-BIT DATA REGISTER INTEGER N IF DIVIDER FROM REFIN PHASE FREQUENCY DETECTOR IFINB IFINA ؋2 DOUBLER 15-BIT R COUNTER CHARGE PUMP CPIF AGND1 AGND2 DGND CPGND1 CPGND2 REV. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However,...