Direct Modulation/Fast Waveform Generating, 13 GHz, Fractional-N Frequency Synthesizer ADF4159 Data Sheet FEATURES GENERAL DESCRIPTION RF bandwidth to 13 GHz High and low speed FMCW ramp generation 25-bit fixed modulus allows subhertz frequency resolution PFD frequencies up to 110 MHz Normalized phase noise floor of -224 dBc/Hz FSK and PSK functions Sawtooth, triangular, and parabolic waveform generation Ramp superimposed with FSK Ramp with 2 different sweep rates Ramp delay, frequency readback, and interrupt functions Programmable phase control 2.7 V to 3.45 V analog power supply 1.8 V digital power supply Programmable charge pump currents 3-wire serial interface Digital lock detect ESD performance: 3000 V HBM, 1000 V CDM Qualified for automotive applications The ADF4159 is a 13 GHz, fractional-N frequency synthesizer with modulation and both fast and slow waveform generation capability. The part uses a 25-bit fixed modulus, allowing subhertz frequency resolution. The ADF4159 consists of a low noise digital phase frequency detector (PFD), a precision charge pump, and a programmable reference divider. The --based fractional interpolator allows programmable fractional-N division. The INT and FRAC registers define an overall N divider as N = INT + (FRAC/225). The ADF4159 can be used to implement frequency shift keying (FSK) and phase shift keying (PSK) modulation. Frequency sweep modes are also available to generate various waveforms in the frequency domain, for example, sawtooth and triangular waveforms. Sweeps can be set to run automatically or with each step manually triggered by an external pulse. The ADF4159 features cycle slip reduction circuitry, which enables faster lock times without the need for modifications to the loop filter. Control of all on-chip registers is via a simple 3-wire interface. The ADF4159 operates with an analog power supply in the range of 2.7 V to 3.45 V and a digital power supply in the range of 1.62 V to 1.98 V. The device can be powered down when not in use. APPLICATIONS FMCW radars Communications test equipment Communications infrastructure FUNCTIONAL BLOCK DIAGRAM AVDD DVDD SDVDD VP RSET ADF4159 /2 DIVIDER + PHASE FREQUENCY DETECTOR CSR DGND LOCK DETECT OUTPUT MUX CP CHARGE PUMP - HIGH-Z MUXOUT SW2 REFERENCE 5-BIT R COUNTER x2 DOUBLER REFIN FAST LOCK SWITCH SDOUT SW1 DVDD RDIV N COUNTER NDIV LE RFINB FRACTION VALUE 32-BIT DATA REGISTER AGND DGND INTEGER VALUE MODULUS 225 VALUE SDGND CPGND 10849-001 CLK RFINA - THIRD-ORDER FRACTIONAL INTERPOLATOR CE TXDATA DATA + Figure 1. Rev. E Document Feedback Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. 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Technical Support www.analog.com ADF4159 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Step Register (R6) Map .............................................................. 23 Applications ....................................................................................... 1 Delay Register (R7) Map ........................................................... 24 General Description ......................................................................... 1 Applications Information .............................................................. 25 Functional Block Diagram .............................................................. 1 Initialization Sequence .............................................................. 25 Revision History ............................................................................... 3 RF Synthesizer Worked Example ............................................. 25 Specifications..................................................................................... 4 Reference Doubler ...................................................................... 25 Timing Specifications .................................................................. 5 Cycle Slip Reduction for Faster Lock Times ........................... 25 Absolute Maximum Ratings ............................................................ 7 Modulation .................................................................................. 26 Thermal Resistance ...................................................................... 7 Waveform Generation ............................................................... 26 ESD Caution .................................................................................. 7 Waveform Deviations and Timing ........................................... 27 Pin Configuration and Function Descriptions ............................. 8 Single Ramp Burst ...................................................................... 27 Typical Performance Characteristics ............................................. 9 Single Triangular Burst .............................................................. 27 Theory of Operation ...................................................................... 11 Single Sawtooth Burst ................................................................ 27 Reference Input Section ............................................................. 11 Sawtooth Ramp........................................................................... 27 RF Input Stage ............................................................................. 11 Triangular Ramp ........................................................................ 27 RF INT Divider ........................................................................... 11 FMCW Radar Ramp Settings Worked Example ...................... 27 25-Bit Fixed Modulus ................................................................ 11 Activating the Ramp .................................................................. 28 INT, FRAC, and R Counter Relationship ................................ 11 Other Waveforms ....................................................................... 28 R Counter .................................................................................... 11 Ramp Complete Signal to MUXOUT ..................................... 31 Phase Frequency Detector (PFD) and Charge Pump ............ 12 External Control of Ramp Steps ............................................... 31 MUXOUT and Lock Detect ...................................................... 12 Interrupt Modes and Frequency Readback ............................ 32 Input Shift Register..................................................................... 12 Fast Lock Mode .......................................................................... 33 Program Modes .......................................................................... 12 Spur Mechanisms ....................................................................... 34 Register Maps .................................................................................. 13 Filter Design Using ADIsimPLL .............................................. 34 FRAC/INT Register (R0) Map .................................................. 15 PCB Design Guidelines for the Chip Scale Package .............. 34 LSB FRAC Register (R1) Map ................................................... 16 Application of the ADF4159 in FMCW Radar........................... 35 R Divider Register (R2) Map .................................................... 17 Outline Dimensions ....................................................................... 36 Function Register (R3) Map...................................................... 19 Ordering Guide .......................................................................... 36 Clock Register (R4) Map ........................................................... 21 Automotive Products ................................................................. 36 Deviation Register (R5) Map .................................................... 22 Rev. E | Page 2 of 36 Data Sheet ADF4159 REVISION HISTORY 7/14--Rev. D to Rev. E 6/13--Rev. A to Rev. B Changed JA from 30.4C/W to 56C/W ........................................ 7 Changes to Single Full Triangle Section .......................................24 Changes to Timeout Interval Section ...........................................27 Changed PFD Antibacklash Pulse from 3 ns to 1 ns in Phase Frequency Detector (PFD) and Charge Pump Section.............. 11 Changes to Charge Pump Current Setting Section and Reference Doubler Section ............................................................ 16 Changes to Negative Bleed Current Enable Section and Loss of Lock (LOL) Section......................................................................... 18 11/13--Rev. C to Rev. D Change to General Description Section ......................................... 1 Moved Revision History Section ..................................................... 3 Changes to Table 1 ............................................................................ 4 Change to 25-Bit Fixed Modulus Section ....................................11 Changes to Loss of Lock (LOL) Section and Lock Detect Precision (LDP) Section .................................................................19 Changes to - Modulator Mode Section, Clock Divider Select Section, and Clock Divider Mode Section ...................................21 Added External Control of Ramp Steps Section and Figure 49; Renumbered Sequentially ..............................................................31 Changes to Fast Lock Timer and Register Sequences Section, Fast Lock Example Section, and Fast Lock Loop Filter Topology Section ..............................................................................................33 Changes to Ordering Guide ...........................................................36 5/13--Revision A: Initial Version 9/13--Rev. B to Rev. C Change to Features Section .............................................................. 1 Change to Figure 2 ............................................................................ 4 Changes to Figure 24 ......................................................................13 Added - Modulator Mode Section...........................................20 Changes to Figure 29 ......................................................................20 Change to Interrupt Modes and Frequency Readback Section ...... 31 Change to Fast Lock Timer and Register Sequences Section ....32 Changes to Ordering Guide ...........................................................35 Added Automotive Products Section ...........................................35 Rev. E | Page 3 of 36 ADF4159 Data Sheet SPECIFICATIONS AVDD = VP = 2.7 V to 3.45 V, DVDD = SDVDD = 1.8 V, AGND = DGND = SDGND = CPGND = 0 V, fPFD = 110 MHz, TA = TMIN to TMAX, dBm referred to 50 , unless otherwise noted. Table 1. Parameter1 RF CHARACTERISTICS RF Input Frequency (RFIN) Prescaler Output Frequency REFERENCE CHARACTERISTICS REFIN Input Frequency Reference Doubler Enabled REFIN Input Capacitance REFIN Input Current PHASE FREQUENCY DETECTOR (PFD) Phase Detector Frequency2 CHARGE PUMP ICP Sink/Source Current High Value Low Value Absolute Accuracy RSET Range ICP Three-State Leakage Current Sink and Source Matching ICP vs. VCP ICP vs. Temperature LOGIC INPUTS Input High Voltage, VINH Input Low Voltage, VINL Input Current, IINH/IINL Input Capacitance, CIN LOGIC OUTPUTS Output High Voltage, VOH Output Low Voltage, VOL Output High Current, IOH POWER SUPPLIES AVDD DVDD, SDVDD VP AIDD Min Typ Max Unit Test Conditions/Comments 13 GHz 2 GHz -10 dBm min to 0 dBm max; for lower frequencies, ensure a slew rate 400 V/s For higher frequencies, use 8/9 prescaler 10 260 MHz 10 50 1.2 100 MHz pF A 110 MHz 0.5 4.59 4.8 300 2.5 5.1 1 2 2 2 5.61 1.17 mA A % k nA % % % 0.4 1 10 V V A pF 0.3 100 V V A 26 3.45 1.98 3.45 40 V V V mA DIDD 7.5 10 mA IP Power-Down Mode 5.5 2 7 mA A DVDD - 0.4 2.7 1.62 2.7 1.8 Rev. E | Page 4 of 36 -5 dBm min to +9 dBm max biased at 1.8/2 (ac coupling ensures 1.8/2 bias); for frequencies < 10 MHz, use a dc-coupled, CMOS-compatible square wave with a slew rate > 25 V/s Bit DB20 in Register R2 set to 1 Programmable RSET = 5.1 k RSET = 5.1 k Sink and source current 0.5 V < VCP < VP - 0.5 V 0.5 V < VCP < VP - 0.5 V VCP = VP/2 CMOS output selected IOL = 500 A Supply current drawn by AVDD; fPFD = 110 MHz Supply current drawn by DVDD; fPFD = 110 MHz Supply current drawn by VP; fPFD = 110 MHz Data Sheet ADF4159 Parameter1 NOISE CHARACTERISTICS Normalized Phase Noise Floor3 Integer-N Mode Fractional-N Mode Normalized 1/f Noise (PN1_f)4 Min Typ Phase Noise Performance5 12,002 MHz Output6 Max Unit -224 -217 -120 dBc/Hz dBc/Hz dBc/Hz -96 dBc/Hz Test Conditions/Comments PLL loop BW = 1 MHz FRAC = 0; see - Modulator Mode section Measured at 10 kHz offset, normalized to 1 GHz At VCO output At 50 kHz offset, 100 MHz PFD frequency 1 Operating temperature: -40C to +125C. Guaranteed by design. Sample tested to ensure compliance. 3 This specification can be used to calculate phase noise for any application. Use the formula ((Normalized Phase Noise Floor) + 10 log(fPFD) + 20 logN) to calculate in-band phase noise performance as seen at the VCO output. 4 The PLL phase noise is composed of flicker (1/f) noise plus the normalized PLL noise floor. The formula for calculating the 1/f noise contribution at an RF frequency (fRF) and at an offset frequency (f) is given by PN = PN1_f + 10 log(10 kHz/f) + 20 log(fRF/1 GHz). Both the normalized phase noise floor and flicker noise are modeled in ADIsimPLL. 5 The phase noise is measured with the EV-ADF4159EB3Z and the Rohde & Schwarz FSUP signal source analyzer. 6 fREFIN = 100 MHz; fPFD = 100 MHz; offset frequency = 50 kHz; RFOUT = 12,002 MHz; N = 120.02; loop bandwidth = 250 kHz. 2 TIMING SPECIFICATIONS AVDD = VP = 2.7 V to 3.45 V, DVDD = SDVDD = 1.8 V, AGND = DGND = SDGND = CPGND = 0 V, TA = TMIN to TMAX, dBm referred to 50 , unless otherwise noted. Table 2. Write Timing Parameter t1 t2 t3 t4 t5 t6 t7 Limit at TMIN to TMAX 20 10 10 25 25 10 20 Unit ns min ns min ns min ns min ns min ns min ns min Description LE setup time DATA to CLK setup time DATA to CLK hold time CLK high duration CLK low duration CLK to LE setup time LE pulse width Write Timing Diagram t4 t5 CLK t2 DATA DB31 (MSB) t3 DB30 DB2 (CONTROL BIT C3) DB1 (CONTROL BIT C2) DB0 (LSB) (CONTROL BIT C1) t7 t1 t6 Figure 2. Write Timing Diagram Rev. E | Page 5 of 36 10849-002 LE ADF4159 Data Sheet Table 3. Read Timing Parameter t11 t2 t3 t4 t5 1 Limit at TMIN to TMAX tPFD + 20 20 25 25 10 Unit ns min ns min ns min ns min ns min Description TXDATA setup time CLK setup time to data (on MUXOUT) CLK high duration CLK low duration CLK to LE setup time tPFD is the period of the PFD frequency; for example, if the PFD frequency is 50 MHz, tPFD = 20 ns. Read Timing Diagram TXDATA t1 t3 t4 CLK t2 MUXOUT DB36 DB2 DB35 DB1 DB0 t5 10849-003 LE NOTES 1. LE SHOULD BE KEPT HIGH DURING READBACK. Figure 3. Read Timing Diagram 500A 0.9V CL 10pF 100A IOH 10849-004 TO MUXOUT PIN IOL Figure 4. Load Circuit for MUXOUT Timing, CL = 10 pF Rev. E | Page 6 of 36 Data Sheet ADF4159 ABSOLUTE MAXIMUM RATINGS TA = 25C, GND = AGND = DGND = SDGND = CPGND = 0 V, unless otherwise noted. Table 4. Parameter AVDD to GND DVDD to GND VP to GND VP to AVDD Digital I/O Voltage to GND Analog I/O Voltage to GND REFIN to GND RFIN to GND Operating Temperature Range, Industrial Storage Temperature Range Maximum Junction Temperature Reflow Soldering Peak Temperature Time at Peak Temperature ESD Charged Device Model Human Body Model Rating -0.3 V to +3.9 V -0.3 V to +2.4 V -0.3 V to +3.9 V -0.3 V to +0.3 V -0.3 V to DVDD + 0.3 V -0.3 V to AVDD + 0.3 V -0.3 V to DVDD + 0.3 V -0.3 V to AVDD + 0.3 V -40C to +125C -65C to +125C 150C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. THERMAL RESISTANCE Thermal impedance (JA) is specified for a device with the exposed pad soldered to AGND. Table 5. Thermal Resistance Package Type 24-Lead LFCSP_WQ ESD CAUTION 260C 40 sec 1000 V 3000 V Rev. E | Page 7 of 36 JA 56 Unit C/W ADF4159 Data Sheet 19 DVDD 21 SW2 20 SW1 22 VP 24 CP 23 RSET PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 18 SDVDD CPGND 1 AGND 2 17 MUXOUT ADF4159 RFINB 4 TOP VIEW (Not to Scale) 16 LE 15 DATA TXDATA 12 SDGND 11 DGND 10 REFIN 9 13 CE AVDD 8 14 CLK AVDD 6 AVDD 7 RFINA 5 NOTES 1. THE LFCSP HAS AN EXPOSED PAD THAT MUST BE CONNECTED TO AGND. 10849-005 AGND 3 Figure 5. Pin Configuration Table 6. Pin Function Descriptions Pin No. 1 2, 3 4 Mnemonic CPGND AGND RFINB 5 6, 7, 8 RFINA AVDD 9 REFIN 10 11 12 DGND SDGND TXDATA 13 CE 14 CLK 15 DATA 16 LE 17 18 MUXOUT SDVDD 19 DVDD 20, 21 22 23 SW1, SW2 VP RSET 24 CP 25 EPAD Description Charge Pump Ground. This pin is the ground return path for the charge pump. Analog Ground. Complementary Input to the RF Prescaler. Decouple this pin to the ground plane with a small bypass capacitor, typically 100 pF. Input to the RF Prescaler. This small signal input is normally ac-coupled from the VCO. Positive Power Supply for the RF Section. Place decoupling capacitors to the ground plane as close as possible to these pins. Reference Input. This CMOS input has a nominal threshold of DVDD/2 and an equivalent input resistance of 100 k. It can be driven from a TTL or CMOS crystal oscillator, or it can be ac-coupled. Digital Ground. Digital - Modulator Ground. This pin is the ground return path for the - modulator. Transmit Data Pin. This pin provides the data to be transmitted in FSK or PSK mode and also controls some ramping functionality. Chip Enable (1.8 V Logic). A logic low on this pin powers down the device and places the charge pump output into three-state mode. Serial Clock Input. This input is used to clock in the serial data to the registers. The data is latched into the input shift register on the CLK rising edge. This input is a high impedance CMOS input. Serial Data Input. The serial data is loaded MSB first; the three LSBs are the control bits. This input is a high impedance CMOS input. Load Enable Input. When LE is high, the data stored in the input shift register is loaded into one of the eight latches; the latch is selected using the control bits. This input is a high impedance CMOS input. Multiplexer Output. This pin allows various internal signals to be accessed externally. Power Supply for the Digital - Modulator. Place decoupling capacitors to the ground plane as close as possible to this pin. Positive Power Supply for the Digital Section. Place decoupling capacitors to the digital ground plane as close as possible to this pin. Switches for Fast Lock. Charge Pump Power Supply. The voltage on this pin must be greater than or equal to AVDD. Connecting a resistor between this pin and ground sets the maximum charge pump output current. The relationship between ICP and RSET is as follows: ICP_MAX = 24.48/RSET where: ICP_MAX = 4.8 mA. RSET = 5.1 k. Charge Pump Output. When the charge pump is enabled, this output provides ICP to the external loop filter, which, in turn, drives the external VCO. Exposed Pad. The LFCSP has an exposed pad that must be connected to AGND. Rev. E | Page 8 of 36 Data Sheet ADF4159 -40 12.06 -60 12.05 12.04 -80 FREQUENCY (GHz) PHASE NOISE (dBc/Hz) TYPICAL PERFORMANCE CHARACTERISTICS -100 -120 12.03 12.02 12.01 -140 12.00 -160 10k 100k 1M 10M 100M FREQUENCY OFFSET (Hz) 11.98 12.05 12.04 12.04 FREQUENCY (GHz) 12.05 12.03 12.02 12.01 11.99 200 TIME (s) 11.98 100 200 300 400 500 TIME (s) 12.06 12.06 12.05 12.05 FREQUENCY (GHz) 12.04 12.03 12.02 12.01 12.04 12.03 12.02 12.01 12.00 0 50 100 150 200 TIME (s) Figure 8. Sawtooth Ramp with Delay, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3, CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64, Delay Word = 1000 11.99 0 100 200 300 400 500 TIME (s) Figure 11. Triangle Ramp, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3, CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64 Rev. E | Page 9 of 36 10849-111 12.00 11.99 10849-108 FREQUENCY (GHz) 0 Figure 10. Dual Sawtooth Ramp, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3; First Ramp: CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64; Second Ramp: CLK2 = 52, DEV = 1024, DEV_OFFSET = 7, Number of Steps = 64 Figure 7. Sawtooth Ramp, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3, CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64 11.98 100 12.01 11.99 150 80 12.02 12.00 100 60 12.03 12.00 10849-107 FREQUENCY (GHz) 12.06 50 40 Figure 9. Sawtooth Burst, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3, CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64 12.06 0 20 TIME (s) Figure 6. Phase Noise at 12.002 GHz, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, Bleed Current = 11.03 A 11.98 0 10849-110 1k 10849-106 -180 100 10849-109 11.99 ADF4159 Data Sheet 12.014 12.06 12.012 12.05 12.04 12.008 FREQUENCY (GHz) FREQUENCY (GHz) 12.010 12.03 12.02 12.006 12.004 12.002 12.000 12.01 11.998 12.00 11.996 50 100 150 200 11.994 TIME (s) Figure 12. Fast Ramp (Triangle Ramp with Different Slopes), fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3; Up Ramp: CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64; Down Ramp: CLK2 = 70, DEV = 16,384, DEV_OFFSET = 8, Number of Steps = 4 0 100 200 300 400 10849-115 0 10849-112 11.99 500 TIME (s) Figure 15. FSK Ramp, fPFD = 100 MHz, ICP = 2.5 mA, Loop Bandwidth = 250 kHz, CLK1 = 3, CLK2 = 26, DEV = 1024, DEV_OFFSET = 8, Number of Steps = 64; FSK: DEV = -512, DEV_OFFSET = 8 200 0 150 -5 100 -10 50 0 -50 -15 -20 -25 -100 -30 -150 -35 0 50 100 150 200 TIME (s) -40 10849-113 -200 0 5 10 15 20 FREQUENCY (GHz) Figure 13. Phase Shift Keying (PSK), Loop Bandwidth = 250 kHz, Phase Value = 1024, Data Rate = 20 kHz 10849-116 RF SENSITIVITY (dBm) PHASE (Degrees) PRESCALER 8/9 PRESCALER 4/5 Figure 16. RFIN Sensitivity at Nominal Temperature 12.004 6 12.003 4 2 ICP (mA) 12.001 12.000 0 11.999 -2 11.998 -4 11.996 0 50 100 150 200 TIME (s) -6 0 0.5 1.0 1.5 2.0 2.5 VCP (V) Figure 17. Charge Pump Output Characteristics Figure 14. Frequency Shift Keying (FSK), Loop Bandwidth = 250 kHz, DEV = 1049, DEV_OFFSET = 9, Data Rate = 20 kHz Rev. E | Page 10 of 36 3.0 10849-117 11.997 10849-114 FREQUENCY (GHz) 12.002 Data Sheet ADF4159 THEORY OF OPERATION REFERENCE INPUT SECTION 25-BIT FIXED MODULUS Figure 18 shows the reference input stage. The SW1 and SW2 switches are normally closed (NC in Figure 18). The SW3 switch is normally open (NO in Figure 18). When power-down is initiated, SW3 is closed, and SW1 and SW2 are opened. In this way, no loading of the REFIN pin occurs during power-down. The ADF4159 has a 25-bit fixed modulus. This modulus allows output frequencies to be spaced with a resolution of POWER-DOWN CONTROL 100k NC SW2 TO R COUNTER REFIN NC BUFFER 10849-013 SW3 RF INPUT STAGE Figure 19 shows the RF input stage. The input stage is followed by a two-stage limiting amplifier to generate the current-mode logic (CML) clock levels required for the prescaler. 1.6V AVDD 2k where fPFD is the frequency of the phase frequency detector (PFD). For example, with a PFD frequency of 100 MHz, frequency steps of 2.98 Hz are possible. Due to the architecture of the - modulator, there is a fixed +(fPFD/226) offset on the VCO output. To remove this offset, see the - Modulator Mode section. The INT and FRAC values, in conjunction with the R counter, make it possible to generate output frequencies that are spaced by fractions of the PFD frequency. Figure 18. Reference Input Stage BIAS GENERATOR (1) INT, FRAC, AND R COUNTER RELATIONSHIP SW1 NO fRES = fPFD/225 2k The RF VCO frequency (RFOUT) equation is RFOUT = (INT + (FRAC/225)) x fPFD (2) where: RFOUT is the output frequency of the external voltage controlled oscillator (VCO). INT is the preset divide ratio of the binary 12-bit counter (23 to 4095). FRAC is the numerator of the fractional division (0 to (225 - 1)). The PFD frequency (fPFD) equation is fPFD = REFIN x [(1 + D)/(R x (1 + T))] RFINA 10849-014 RFINB AGND RF INT DIVIDER The RF INT CMOS divider allows a division ratio in the PLL feedback counter. Division ratios from 23 to 4095 are allowed. The 5-bit R counter allows the input reference frequency (REFIN) to be divided down to supply the reference clock to the PFD. Division ratios from 1 to 32 are allowed. N = INT + FRAC/MOD TO PFD N COUNTER THIRD-ORDER FRACTIONAL INTERPOLATOR INT VALUE MOD VALUE FRAC VALUE 10849-015 FROM RF INPUT STAGE where: REFIN is the reference input frequency. D is the REFIN doubler bit (0 or 1). R is the preset divide ratio of the binary 5-bit programmable reference (R) counter (1 to 32). T is the REFIN divide-by-2 bit (0 or 1). R COUNTER Figure 19. RF Input Stage RF INT DIVIDER (3) Figure 20. RF INT Divider Rev. E | Page 11 of 36 ADF4159 Data Sheet PHASE FREQUENCY DETECTOR (PFD) AND CHARGE PUMP INPUT SHIFT REGISTER The ADF4159 digital section includes a 5-bit R counter, a 12-bit INT counter, and a 25-bit FRAC counter. Data is clocked into the 32-bit input shift register on each rising edge of CLK. The data is clocked in MSB first. Data is transferred from the input shift register to one of eight latches on the rising edge of LE. The PFD takes inputs from the R counter and N counter and produces an output proportional to the phase and frequency difference between them. Figure 21 shows a simplified schematic of the PFD. HIGH D1 Q1 The destination latch is determined by the state of the three control bits (C3, C2, and C1) in the input shift register. As shown in Figure 2, the control bits are the three LSBs (DB2, DB1, and DB0, respectively). Table 7 shows the truth table for these bits. Figure 23 and Figure 24 provide a summary of how the latches are programmed. UP U1 +IN CLR1 DELAY CHARGE PUMP U3 CP Table 7. Truth Table for the C3, C2, and C1 Control Bits HIGH CLR2 DOWN Q2 D2 10849-016 U2 C3 0 0 0 0 1 1 1 1 -IN Figure 21. PFD Simplified Schematic The PFD includes a fixed delay element that sets the width of the antibacklash pulse, which is typically 1 ns. This pulse ensures that there is no dead zone in the PFD transfer function and gives a consistent reference spur level. MUXOUT AND LOCK DETECT The following settings in the ADF4159 are double buffered: LSB fractional value, phase value, charge pump current setting, reference divide-by-2, reference doubler, R counter value, and CLK1 divider value. Before the part uses a new value for any double-buffered setting, the following two events must occur: DVDD DGND 1. R DIVIDER OUTPUT 2. N DIVIDER OUTPUT CONTROL MUXOUT DIGITAL LOCK DETECT SERIAL DATA OUTPUT CLK DIVIDER OUTPUT N DIVIDER/2 DGND 10849-017 R DIVIDER/2 READBACK TO MUXOUT Register R0 R1 R2 R3 R4 R5 R6 R7 Table 7 and Figure 25 through Figure 32 show how the program modes are set up in the ADF4159. DVDD MUX C1 0 1 0 1 0 1 0 1 PROGRAM MODES The multiplexer output on the ADF4159 allows the user to access various internal points on the chip. The state of MUXOUT is controlled by the M4, M3, M2, and M1 bits in Register R0 (see Figure 25). Figure 22 shows the MUXOUT section in block diagram form. THREE-S TATE OUTPUT Control Bits C2 0 0 1 1 0 0 1 1 The new value is latched into the device by writing to the appropriate register. A new write is performed to Register 0 (R0). For example, updating the fractional value involves a write to the 13 LSB bits in R1 and the 12 MSB bits in R0. R1 must be written to first, followed by the write to R0. The frequency change begins after the write to R0. Double-buffering ensures that the bits written to R1 do not take effect until after the write to R0. Figure 22. MUXOUT Schematic Rev. E | Page 12 of 36 Data Sheet ADF4159 REGISTER MAPS RAMP ON FRAC/INT REGISTER (R0) MUXOUT CONTROL 12-BIT MSB FRACTIONAL VALUE (FRAC) 12-BIT INTEGER VALUE (INT) CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 R1 M4 M3 M2 M1 N12 N10 N11 N9 N8 N7 N6 N5 N4 N3 N2 N1 F25 F24 F23 F22 F21 F20 F19 F18 F17 F16 F15 F14 C3(0) C2(0) C1(0) LSB FRAC REGISTER (R1) PHASE ADJUST DBB RESERVED DBB 13-BIT LSB FRACTIONAL VALUE (FRAC) CONTROL BITS 12-BIT PHASE VALUE DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 P1 F13 F12 F10 F11 F9 F8 F7 F6 F5 F4 F3 F2 F1 P12 P11 P10 P8 P9 P7 P6 P5 P4 P3 P2 P1 C3(0) C2(0) C1(1) R DIVIDER REGISTER (R2) RDIV2 DBB DBB REFERENCE DOUBLER DBB PRESCALER CP CURRENT SETTING CSR RESERVED RESERVED DBB DBB 5-BIT R COUNTER CONTROL BITS 12-BIT CLK1 DIVIDER VALUE 0 P1 U2 U1 R5 R4 R3 R2 R1 D12 D11 D10 D8 D9 D7 D6 D5 D4 D3 POWER-DOWN CR1 CPI4 CPI3 CPI2 CPI1 PD POLARITY 0 LDP 0 FSK 0 PSK DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 D2 D1 C3(0) C2(1) C1(0) CP THREE-STATE COUNTER RESET RAMP MODE RESERVED SD RESET N SEL RESERVED LOL NEG BLEED CURRENT RESERVED RESERVED NEG BLEED ENABLE FUNCTION REGISTER (R3) CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 0 0 0 NB3 NB2 NB1 0 0 0 0 1 L1 NS1 U12 0 0 RM2 RM1 0 0 U11 U10 U9 U8 U7 C3(0) C2(1) C1(1) 10849-018 0 NOTES 1. DBB = DOUBLE-BUFFERED BITS. Figure 23. Register Summary 1 Rev. E | Page 13 of 36 ADF4159 Data Sheet - MODULATOR MODE CLK DIV MODE RAMP STATUS CLK DIV SEL LE SEL CLOCK REGISTER (R4) 12-BIT CLK2 DIVIDER VALUE RESERVED CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 LS1 S5 S4 S3 S2 S1 R5 R4 R3 R2 R1 C2 C1 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 CS1 0 0 0 C3(1) C2(0) C1(0) DEV SEL DUAL RAMP FSK RAMP INTERRUPT PARABOLIC RAMP TX RAMP CLK TXDATA INVERT RESERVED DEVIATION REGISTER (R5) 4-BIT DEVIATION OFFSET WORD CONTROL BITS 16-BIT DEVIATION WORD DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 TR1 0 I2 I1 0 0 DS1 DO4 DO3 DO2 DO1 D16 D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 C3(1) C2(0) C1(1) STEP SEL STEP REGISTER (R6) RESERVED CONTROL BITS 20-BIT STEP WORD DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 0 0 0 0 0 SSE1 S20 S19 S18 S17 S16 S15 S14 S13 S12 S11 S10 S9 S8 S7 S6 S5 S4 S3 S2 S1 C3(1) C2(1) C1(0) DEL START EN DEL CLK SEL RAMP DELAY RAMP DELAY FL FAST RAMP TXDATA TRIGGER SING FULL TRI RESERVED TRI DELAY TXDATA TRIGGER DELAY DELAY REGISTER (R7) 12-BIT DELAY START WORD CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 0 0 0 0 0 TD1 ST1 TR1 FR1 0 RD1 DC1 DSE1 DS12 DS11 DS10 DS9 DS8 DS7 DS6 DS5 DS4 DS3 DS2 DS1 C3(1) C2(1) C1(1) 10849-019 0 NOTES 1. DBB = DOUBLE-BUFFERED BITS. Figure 24. Register Summary 2 Rev. E | Page 14 of 36 Data Sheet ADF4159 FRAC/INT REGISTER (R0) MAP 12-Bit Integer Value (INT) When Bits DB[2:0] are set to 000, the on-chip FRAC/INT register (Register R0) is programmed (see Figure 25). Bits DB[26:15] set the INT value, which forms part of the overall feedback division factor. For more information, see the INT, FRAC, and R Counter Relationship section. Ramp On 12-Bit MSB Fractional Value (FRAC) When Bit DB31 is set to 1, the ramp function is enabled. When Bit DB31 is set to 0, the ramp function is disabled. Bits DB[14:3], along with Bits DB[27:15] in the LSB FRAC register (Register R1), set the FRAC value that is loaded into the fractional interpolator. The FRAC value forms part of the overall feedback division factor. These 12 bits are the most significant bits (MSBs) of the 25-bit FRAC value; Bits DB[27:15] in the LSB FRAC register (Register R1) are the least significant bits (LSBs). For more information, see the RF Synthesizer Worked Example section. MUXOUT Control RAMP ON The on-chip multiplexer of the ADF4159 is controlled by Bits DB[30:27]. See Figure 25 for the truth table. MUXOUT CONTROL 12-BIT MSB FRACTIONAL VALUE (FRAC) 12-BIT INTEGER VALUE (INT) CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 M4 M3 M2 R1 RAMP ON M1 N12 N11 M4 M3 M2 N10 N9 M1 N8 N7 N6 N5 N4 N3 N2 N1 F25 F24 F23 OUTPUT 0 RAMP DISABLED 0 0 0 0 THREE-STATE OUTPUT 1 RAMP ENABLED 0 0 0 1 DVDD 0 0 1 0 DGND 0 0 1 1 R DIVIDER OUTPUT 0 1 0 0 N DIVIDER OUTPUT 0 1 0 1 RESERVED 0 1 1 0 DIGITAL LOCK DETECT 0 1 1 1 SERIAL DATA OUTPUT 1 0 0 0 RESERVED 1 0 0 1 RESERVED 1 0 1 0 CLK DIVIDER OUTPUT 1 0 1 1 RESERVED 1 1 0 0 RESERVED 1 1 0 1 R DIVIDER/2 1 1 1 0 N DIVIDER/2 1 1 1 1 READBACK TO MUXOUT F22 F21 F20 F19 F18 F17 F16 F15 F14 C3(0) C2(0) C1(0) MSB FRACTIONAL VALUE (FRAC)* F25 F24 ... F15 F14 0 0 ... 0 0 0 0 0 ... 0 1 1 0 0 ... 1 0 2 0 0 ... 1 1 3 . . ... . . . . . ... . . . . . ... . . . 1 1 ... 0 0 4092 1 1 ... 0 1 4093 1 1 ... 1 0 4094 1 1 ... 1 1 4095 *THE FRAC VALUE IS MADE UP OF THE 12-BIT MSB STORED IN REGISTER R0 AND THE 13-BIT LSB STORED IN REGISTER R1. FRAC VALUE = 13-BIT LSB + 12-BIT MSB x 213. N12 N11 N10 N9 N8 N7 N6 N5 N4 N3 N2 N1 0 0 0 0 0 0 0 1 0 1 1 1 23 0 0 0 0 0 0 0 1 1 0 0 0 24 0 0 0 0 0 0 0 1 1 0 0 1 25 0 0 0 0 0 0 0 1 1 0 1 0 26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 1 1 1 1 1 1 1 1 0 1 4093 1 1 1 1 1 1 1 1 1 1 1 0 4094 1 1 1 1 1 1 1 1 1 1 1 1 4095 Figure 25. FRAC/INT Register (R0) Map Rev. E | Page 15 of 36 INTEGER VALUE (INT) 10849-020 R1 ADF4159 Data Sheet LSB FRAC REGISTER (R1) MAP These 13 bits are the least significant bits (LSBs) of the 25-bit FRAC value; Bits DB[14:3] in the FRAC/INT register are the most significant bits (MSBs). For more information, see the RF Synthesizer Worked Example section. When Bits DB[2:0] are set to 001, the on-chip LSB FRAC register (Register R1) is programmed (see Figure 26). Reserved Bits 12-Bit Phase Value All reserved bits must be set to 0 for normal operation. Bits DB[14:3] control the phase word. The phase word is used to increase the RF output phase relative to the current phase. The phase change occurs after a write to Register R0. Phase Adjustment Bit DB28 enables and disables phase adjustment. The phase shift is generated by the value programmed in Bits DB[14:3]. Phase Shift = (Phase Value x 360)/212 13-Bit LSB Fractional Value (FRAC) For example, Phase Value = 512 increases the phase by 45. RESERVED PHASE ADJ Bits DB[27:15], along with Bits DB[14:3] in the FRAC/INT register (Register R0), set the FRAC value that is loaded into the fractional interpolator. The FRAC value forms part of the overall feedback division factor. To use phase adjustment, Bit DB28 must be set to 1. If phase adjustment is not used, it is recommended that the phase value be set to 0. DBB DBB 13-BIT LSB FRACTIONAL VALUE (FRAC) CONTROL BITS 12-BIT PHASE VALUE DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 P1 F13 F12 F11 F10 F9 F8 F7 F13 F12 ... F2 F1 F6 F5 F4 F3 F2 F1 P12 P11 LSB FRACTIONAL VALUE (FRAC)* P10 P9 P8 P7 P6 P5 P4 P3 P2 P1 C3(0) C2(0) C1(1) P12 P11 ... P2 P1 PHASE VALUE P1 PHASE ADJ 0 0 ... 0 0 0 0 1 ... 1 1 2047 0 DISABLED 0 0 ... 0 1 1 . . ... . . . 1 ENABLED 0 0 ... 1 0 2 0 0 ... 1 1 3 0 0 ... 1 1 3 0 0 ... 1 0 2 . . ... . . . 0 0 ... 0 1 1 . . ... . . . 0 0 ... 0 0 0 (RECOMMENDED) . . ... . . . 1 1 ... 1 1 -1 1 1 ... 0 0 8188 1 1 ... 1 0 -2 1 1 ... 0 1 8189 1 1 ... 0 1 -3 1 1 ... 1 0 8190 . . ... . . . 1 1 ... 1 1 8191 1 0 ... 0 0 -2048 *THE FRAC VALUE IS MADE UP OF THE 12-BIT MSB STORED IN REGISTER R0 AND THE 13-BIT LSB STORED IN REGISTER R1. FRAC VALUE = 13-BIT LSB + 12-BIT MSB x 213. NOTES 1. DBB = DOUBLE-BUFFERED BITS. Figure 26. LSB FRAC Register (R1) Map Rev. E | Page 16 of 36 10849-021 0 Data Sheet ADF4159 R DIVIDER REGISTER (R2) MAP When Bits DB[2:0] are set to 010, the on-chip R divider register (Register R2) is programmed (see Figure 27). Reserved Bits All reserved bits must be set to 0 for normal operation. when operating the ADF4159 at frequencies greater than 8 GHz, the prescaler must be set to 8/9. The prescaler limits the INT value as follows: * * Prescaler = 4/5: NMIN = 23 Prescaler = 8/9: NMIN = 75 CSR Enable RDIV2 When Bit DB28 is set to 1, cycle slip reduction (CSR) is enabled. Cycle slip reduction is a method for improving lock times. Note that the signal at the PFD must have a 50% duty cycle for cycle slip reduction to work. In addition, the charge pump current setting must be set to its minimum value. For more information, see the Cycle Slip Reduction for Faster Lock Times section. When Bit DB21 is set to 1, a divide-by-2 toggle flip-flop is inserted between the R counter and the PFD. This feature can be used to provide a 50% duty cycle signal at the PFD. The cycle slip reduction feature can be used only when the phase detector polarity setting is positive (Bit DB6 = 1 in Register R3). CSR cannot be used if the phase detector polarity setting is negative (Bit DB6 = 0 in Register R3). Charge Pump Current Setting Bits DB[27:24] set the charge pump current (see Figure 27). Set these bits to the charge pump current that the loop filter is designed with. Best practice is to design the loop filter for a charge pump current of 2.5 mA or 2.81 mA and then use the programmable charge pump current to tweak the frequency response. See the Reference Doubler section for information on setting the charge pump current when the doubler is enabled. Prescaler (P/P + 1) Reference Doubler When Bit DB20 is set to 0, the reference doubler is disabled, and the REFIN signal is fed directly to the 5-bit R counter. When Bit DB20 is set to 1, the reference doubler is enabled, and the REFIN frequency is multiplied by a factor of 2 before the signal is fed into the 5-bit R counter. When the doubler is disabled, the REFIN falling edge is the active edge at the PFD input to the fractional synthesizer. When the doubler is enabled, both the rising and falling edges of REFIN become active edges at the PFD input. When the reference doubler is enabled, for optimum phase noise performance, it is recommended to only use charge pump current settings 0b0000 to 0b0111, that is, 0.31 mA to 2.5 mA. In this case, best practice is to design the loop filter to for a charge pump current of 1.25 mA or 1.57 mA and then use the programmable charge pump current to tweak the frequency response. 5-Bit R Counter The dual-modulus prescaler (P/P + 1), along with the INT, FRAC, and fixed modulus values, determines the overall division ratio from RFIN to the PFD input. Bit DB22 sets the prescaler value. The 5-bit R counter (Bits DB[19:15]) allows the input reference frequency (REFIN) to be divided down to supply the reference clock to the PFD. Division ratios from 1 to 32 are allowed. Operating at CML levels, the prescaler takes the clock from the RF input stage and divides it down for the counters. The prescaler is based on a synchronous 4/5 core. When the prescaler is set to 4/5, the maximum RF frequency allowed is 8 GHz. Therefore, Bits DB[14:3] program the CLK1 divider value, which determines the duration of the time step in ramp mode. 12-Bit CLK1 Divider Value Rev. E | Page 17 of 36 DBB REFERENCE DOUBLER DBB RESERVED RDIV2 DBB CSR DBB CP CURRENT SETTING PRESCALER Data Sheet RESERVED ADF4159 DBB 5-BIT R COUNTER CONTROL BITS 12-BIT CLK1 DIVIDER VALUE DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 CR1 CR1 CPI4 CPI3 CPI2 CPI1 0 P1 U2 CYCLE SLIP REDUCTION 0 DISABLED 1 ENABLED U1 R5 R4 U1 REFERENCE DOUBLER R1 R2 R3 D11 D12 D10 D8 D9 D7 0 DISABLED D12 D11 ... D2 D1 1 ENABLED 0 0 0 0 . . . 1 1 1 1 0 0 0 0 . . . 1 1 1 1 ... ... ... ... ... ... ... ... ... ... ... 0 0 1 1 . . . 0 0 1 1 0 1 0 1 . . . 0 1 0 1 U2 R DIVIDER 0 DISABLED 1 ENABLED ICP (mA) CPI4 CPI3 CPI2 CPI1 0 0 0 0 5.1k 0.31 P1 0 0 0 1 0.63 0 4/5 0 0 1 0 0.94 1 8/9 0 0 1 1 1.25 0 1 0 0 1.57 0 1 0 1 1.88 R5 R4 R3 R2 R1 0 1 1 0 2.19 0 0 0 0 1 1 0 1 1 1 2.5 0 0 0 1 0 2 1 0 0 0 2.81 0 0 0 1 1 3 1 0 0 1 3.13 0 0 1 0 0 4 1 0 1 0 3.44 . . . . . 1 0 1 1 3.75 . . . . . 1 1 0 0 4.06 . . . . . 1 1 0 1 4.38 1 1 1 0 1 29 1 1 1 0 4.69 1 1 1 1 0 30 1 1 1 1 5.0 1 1 1 1 1 31 0 0 0 0 0 32 PRESCALER D6 D5 D4 D3 D2 D1 C3(0) C2(1) C1(0) CLK 1 DIVIDER VALUE 0 1 2 3 . . . 4092 4093 4094 4095 R COUNTER DIVIDE RATIO NOTES 1. DBB = DOUBLE-BUFFERED BITS. Figure 27. R Divider Register (R2) Map Rev. E | Page 18 of 36 10849-022 0 Data Sheet ADF4159 FUNCTION REGISTER (R3) MAP - Reset When Bits DB[2:0] are set to 011, the on-chip function register (Register R3) is programmed (see Figure 28). For most applications, Bit DB14 should be set to 0. When this bit is set to 0, the - modulator is reset on each write to Register R0. If it is not required that the - modulator be reset on each write to Register R0, set this bit to 1. Reserved Bits All reserved bits except Bit DB17 must be set to 0 for normal operation. Bit DB17 must be set to 1 for normal operation. Negative Bleed Current Bits DB[24:22] set the negative bleed current value (IBLEED). Calculate IBLEED using the following formula, and then select the value of Bits DB[24:22] that is closest to the calculated value. IBLEED = (4 x ICP)/N where: ICP is the charge pump current. N is the N counter value. Ramp Mode Bits DB[11:10] determine the type of generated waveform (see Figure 28 and the Waveform Generation section). PSK Enable When Bit DB9 is set to 1, PSK modulation is enabled. When this bit is set to 0, PSK modulation is disabled. For more information, see the Phase Shift Keying (PSK) section. FSK Enable Negative Bleed Current Enable DB21 enables a negative bleed current in the charge pump. When the charge pump is operating in a nonlinear region, phase noise and spurious performance can degrade. Negative bleed current operates by pushing the charge pump operation region away from this nonlinear region. The programmability feature controls how far the region of operation is moved. If the current is too little, the charge pump will remain in the nonlinear region; if the current is too high, the charge pump will become unstable or degrade the maximum PFD frequency. It is necessary to experiment with various charge pump currents to find the optimum. The formula for calculating the optimum negative bleed current is shown in the Negative Bleed Current section; however, experimentation may show a different current gives the optimum result. Loss of Lock (LOL) Bit DB16 enables or disables the loss of lock indication. When this bit is set to 0, the part indicates loss of lock even when the reference is removed. This feature provides an advantage over the standard implementation of lock detect. For more robust operation, set this bit to 1. The loss of lock does not operate as expected when negative bleed current is enabled. N SEL Bit DB15 can be used to circumvent the issue of pipeline delay between updates of the integer and fractional values in the N counter. Typically, the INT value is loaded first, followed by the FRAC value. This can cause the N counter value to be incorrect for a brief period of time equal to the pipeline delay (about four PFD cycles). This delay has no effect if the INT value was not updated. However, if the INT value has changed, this incorrect N counter value can cause the PLL to overshoot in frequency while it tries to lock to the temporarily incorrect N counter value. After the correct fractional value is loaded, the PLL quickly locks to the correct frequency. Introducing an additional delay to the loading of the INT value using the N SEL bit causes the INT and FRAC values to be loaded at the same time, preventing frequency overshoot. The delay is turned on by setting Bit DB15 to 1. When Bit DB8 is set to 1, FSK modulation is enabled. When this bit is set to 0, FSK modulation is disabled. For more information, see the Frequency Shift Keying (FSK) section. Lock Detect Precision (LDP) The digital lock detect circuit monitors the PFD up and down pulses (logical OR of the up and down pulses; see Figure 21). Every 32nd pulse is measured. The LDP bit (Bit DB7) specifies the length of each lock detect reference cycle. * * LDP = 0: if five consecutive pulses of less than 14 ns are measured, digital lock detect is asserted. LDP = 1: if five consecutive pulses of less than 6 ns are measured, digital lock detect is asserted. Digital lock detect remains asserted until the pulse width exceeds 22 ns, a write to Register R0 occurs, or the part is powered down. For more robust operation, set LDP = 1. Phase Detector (PD) Polarity Bit DB6 sets the phase detector polarity. When the VCO characteristics are positive, set this bit to 1. When the VCO characteristics are negative, set this bit to 0. Power-Down Bit DB5 provides the programmable power-down mode. Setting this bit to 1 performs a power-down. Setting this bit to 0 returns the synthesizer to normal operation. When the part is in software power-down mode, it retains all information in its registers. The register contents are lost only when the supplies are removed. When power-down is activated, the following events occur: * * * * * * Rev. E | Page 19 of 36 All active dc current paths are removed. The RF synthesizer counters are forced to their load state conditions. The charge pump is forced into three-state mode. The digital lock detect circuitry is reset. The RFIN input is debiased. The input shift register remains active and capable of loading and latching data. ADF4159 Data Sheet CP THREE-STATE COUNTER RESET POWER-DOWN PD POLARITY LDP FSK PSK RESERVED - RESET RESERVED N SEL NEG BLEED CURRENT RESERVED RAMP MODE Bit DB3 is the RF counter reset bit. When this bit is set to 1, the RF synthesizer counters are held in reset. For normal operation, set this bit to 0. LOL When Bit DB4 is set to 1, the charge pump is placed into threestate mode. For normal charge pump operation, set this bit to 0. RESERVED Counter Reset NEG BLEED EN Charge Pump Three-State CONTROL BITS DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 0 0 0 NEG BLEED EN 0 DISABLED 1 ENABLED 0 NB3 NB2 NB1 0 0 0 1 L1 NS1 U12 U12 L1 LOL 0 ENABLED 1 DISABLED 0 0 RM2 RM1 0 0 U11 U10 U9 U8 U7 C3(0) C2(1) C1(1) U7 COUNTER RESET 0 DISABLED 1 ENABLED - RESET 0 ENABLED 1 DISABLED U8 NS1 NB3 NB2 NB1 0 CP THREE-STATE 0 DISABLED 1 ENABLED N SEL 0 N WORD LOAD ON - CLOCK 1 N WORD LOAD DELAYED 4 CYCLES U9 POWER-DOWN 0 DISABLED 1 ENABLED NEGATIVE BLEED CURRENT (A) RM2 RM1 RAMP MODE 0 0 0 3.73 0 0 1 11.03 0 0 CONTINUOUS SAWTOOTH 0 NEGATIVE 0 1 0 25.25 0 1 CONTINUOUS TRIANGULAR 1 POSITIVE 0 1 1 53.1 1 0 SINGLE SAWTOOTH BURST 1 1 0 0 0 1 109.7 1 1 SINGLE RAMP BURST 1 1 1 1 0 1 454.7 U10 U11 224.7 916.4 0 0 Figure 28. Function Register (R3) Map Rev. E | Page 20 of 36 PD POLARITY LDP 0 14ns 1 6ns FSK 0 DISABLED 1 ENABLED PSK 0 DISABLED 1 ENABLED 10849-023 0 Data Sheet ADF4159 CLOCK REGISTER (R4) MAP * When Bits DB[2:0] are set to 100, the on-chip clock register (Register R4) is programmed (see Figure 29). * LE SEL In some applications, it is necessary to synchronize the LE pin with the reference signal. To do this, Bit DB31 must be set to 1. Synchronization is done internally on the part. * - Modulator Mode When using the readback to MUXOUT or ramp complete to MUXOUT option, the MUXOUT bits in Register R0 (Bits DB[30:27]) must be set to 1111. To completely disable the - modulator, set Bits DB[30:26] to 0b01110, which puts the ADF4159 into integer-N mode, and the channel spacing becomes equal to the PFD frequency. Both the 12-bit MSB fractional value (Register R0, DB[14:3]) and the 13-bit LSB fractional value (Register R1, DB[27:15]) must be set to 0. After writing to Register 4, Register 3 must be written to twice, to trigger a counter reset. (That is, write Register 3 with DB3 = 1, then write Register 3 with DB3 = 0.) Clock Divider Mode Bits DB[20:19] are used to enable Ramp Divider mode or Fast Lock Divider mode. If neither is being used, set these bits to 0b00. 12-Bit CLK2 Divider Value Bits DB[18:7] program the clock divider (the CLK2 timer) when the part operates in ramp mode (see the Timeout Interval section). The CLK2 timer also determines how long the loop remains in wideband mode when fast lock mode is used (see the Fast Lock Mode section). All features driven by the - modulator are disabled, such as ramping, PSK, FSK, and phase adjust. Disabling the - modulator also removes the fixed +(fPFD/226) offset on the VCO output. Clock Divider Select For normal operation, set these bits to 0b00000. CLK DIV MODE RAMP STATUS 12-BIT CLK2 DIVIDER VALUE DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 LS1 S5 S4 S3 S2 S5 S4 S3 S2 S1 0 0 0 1 0 1 0 1 0 0 S1 R5 R4 R3 R1 C2 C1 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 NORMAL OPERATION DISABLED WHEN FRAC = 0 0 0 0 1 1 0 0 0 0 0 LE SEL 0 LE FROM PIN 1 LE SYNCH WITH REFIN 0 0 0 0 0 0 1 1 0 0 0 0 1 0 1 RAMP STATUS NORMAL OPERATION READBACK TO MUXOUT RAMP COMPLETE TO MUXOUT CHARGE PUMP UP CHARGE PUMP DOWN C2 C1 0 0 1 1 0 1 0 1 CS1 CS1 - MODULATOR MODE R5 R4 R3 R2 R1 LS1 R2 CLOCK DIVIDER MODE CLOCK DIVIDER OFF FAST LOCK DIVIDER RESERVED RAMP DIVIDER D12 D11 ... D2 D1 0 0 0 0 . . . 1 1 1 1 0 0 0 0 . . . 1 1 1 1 ... ... ... ... ... ... ... ... ... ... ... 0 0 1 1 . . . 0 0 1 1 0 1 0 1 . . . 0 1 0 1 Figure 29. Clock Register (R4) Map Rev. E | Page 21 of 36 RESERVED CONTROL BITS DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 C3(1) C2(0) C1(0) CLK DIV SEL 0 LOAD CLK DIV 1 1 LOAD CLK DIV 2 CLK2 DIVIDER VALUE 0 1 2 3 . . . 4092 4093 4094 4095 10849-024 LE SEL Bits DB[25:21] provide access to the following advanced features (see Figure 29): CLK DIV SEL When Bit DB6 is set to 0, CLK2 is used as the CLK2 value for a standard ramp, such as sawtooth or triangular. When Bit DB6 is set to 1, CLK2 is used as the CLK2 value for the second ramp of the Fast Ramp or Dual Ramp functions. For more information, see the Waveform Deviations and Timing section. Ramp Status - MODULATOR MODE Readback to MUXOUT option: the synthesizer frequency at the moment of interruption can be read back (see the Interrupt Modes and Frequency Readback section). Ramp complete to MUXOUT option: a logic high pulse is output on the MUXOUT pin at the end of each ramp. Charge pump up and charge pump down options: the charge pump is forced to constantly output up or down pulses, respectively. ADF4159 Data Sheet DEVIATION REGISTER (R5) MAP Interrupt When Bits DB[2:0] are set to 101, the on-chip deviation register (Register R5) is programmed (see Figure 30). Bits DB[27:26] determine which type of interrupt is used. This feature is used for reading back the INT and FRAC value of a ramp at a given moment in time (a rising edge on the TXDATA pin triggers the interrupt). From the INT and FRAC bits, the frequency can be obtained. After readback, the sweep can continue or stop at the readback frequency. For more information, see the Interrupt Modes and Frequency Readback section. Reserved Bit The reserved bit must be set to 0 for normal operation. TXDATA Invert When Bit DB30 is set to 0, events triggered by TXDATA occur on the rising edge of the TXDATA pulse. When Bit DB30 is set to 1, events triggered by TXDATA occur on the falling edge of the TXDATA pulse. FSK Ramp Enable When Bit DB25 is set to 1, the FSK ramp is enabled. When Bit DB25 is set to 0, the FSK ramp is disabled. TXDATA Ramp Clock Dual Ramp Enable When Bit DB29 is set to 0, the clock divider clock is used to clock the ramp. When Bit DB29 is set to 1, the TXDATA clock is used to clock the ramp. When Bit DB24 is set to 1, the second ramp is enabled. When Bit DB24 is set to 0, the second ramp is disabled. Deviation Select Parabolic Ramp When Bit DB23 is set to 0, the first deviation word is selected. When Bit DB23 is set to 1, the second deviation word is selected. When Bit DB28 is set to 1, the parabolic ramp is enabled. When Bit DB28 is set to 0, the parabolic ramp is disabled. For more information, see the Parabolic (Nonlinear) Ramp Mode section. 4-Bit Deviation Offset Word Bits DB[22:19] determine the deviation offset word. The deviation offset word affects the deviation resolution. 16-Bit Deviation Word DEV SEL DUAL RAMP FSK RAMP INTERRUPT TXDATA RAMP CLK PARABOLIC RAMP TXDATA INVERT RESERVED Bits DB[18:3] determine the signed deviation word. The deviation word defines the deviation step. 4-BIT DEVIATION OFFSET WORD CONTROL BITS 16-BIT DEVIATION WORD DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 TR1 0 I2 I1 0 0 D15 D14 DS1 DO4 DO3 DO2 DO1 D16 DS1 TXDATA INVERT 0 DUAL RAMP 0 DISABLED 0 DISABLED 0 DEV WORD 1 1 ENABLED 1 ENABLED 1 DEV WORD 2 0 1 CLK DIV TXDATA 0 FSK RAMP 0 DISABLED 1 ENABLED D12 D11 D10 D9 D8 D6 D7 D5 D4 D3 D2 D1 C3(1) C2(0) C1(1) DEV SEL 0 TR1 TXDATA RAMP CLK D13 D16 D15 ... D2 D1 0 1 ... 1 1 DEVIATION WORD 32,767 . . ... . . . DEV OFFSET WORD 0 0 ... 1 1 3 0 0 0 0 0 0 0 ... 1 0 2 0 0 0 1 1 0 0 ... 0 1 1 DO4 DO3 DO2 DO1 0 PARABOLIC RAMP 0 0 1 0 2 0 0 ... 0 0 0 0 DISABLED . . . . . 1 1 ... 1 1 -1 1 ENABLED . . . . . 1 1 ... 1 0 -2 0 1 1 1 7 1 1 0 1 -3 . 1 . 0 ... ... ... . 0 . 0 . -32,768 I1 INTERRUPT 1 0 0 0 8 0 0 INTERRUPT OFF 1 0 0 1 9 0 1 LOAD CHANNEL CONTINUE SWEEP 1 0 NOT USED 1 1 LOAD CHANNEL STOP SWEEP 10849-025 I2 Figure 30. Deviation Register (R5) Map Rev. E | Page 22 of 36 Data Sheet ADF4159 Step Select When Bits DB[2:0] are set to 110, the on-chip step register (Register R6) is programmed (see Figure 31). When Bit DB23 is set to 0, Step Word 1 is selected. When Bit DB23 is set to 1, Step Word 2 is selected. Reserved Bits 20-Bit Step Word All reserved bits must be set to 0 for normal operation. Bits DB[22:3] determine the step word. The step word is the number of steps in the ramp. STEP SEL STEP REGISTER (R6) MAP RESERVED CONTROL BITS 20-BIT STEP WORD DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 DB8 DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0 0 0 0 0 0 0 0 SSE1 S20 S19 S18 SSE1 STEP SEL 0 STEP WORD 1 1 STEP WORD 2 S17 S16 S15 S14 S13 S12 S11 S10 S20 S19 ... S2 S1 0 0 0 0 . . . 1 1 1 1 0 0 0 0 . . . 1 1 1 1 ... ... ... ... ... ... ... ... ... ... ... 0 0 1 1 . . . 0 0 1 1 0 1 0 1 . . . 0 1 0 1 Figure 31. Step Register (R6) Map Rev. E | Page 23 of 36 S9 S8 S7 S6 S5 S4 S3 S2 S1 C3(1) C2(1) C1(0) STEP WORD 0 1 2 3 . . . 1,048,572 1,048,573 1,048,574 1,048,575 10849-026 0 ADF4159 Data Sheet DELAY REGISTER (R7) MAP Fast Ramp When Bits DB[2:0] are set to 111, the on-chip delay register (Register R7) is programmed (see Figure 32). When Bit DB19 is set to 1, the triangular waveform is activated with two different slopes. This waveform can be used as an alternative to the sawtooth ramp because it mitigates the overshoot at the end of the ramp in a waveform. Fast ramp is achieved by changing the top frequency to the bottom frequency in a series of small steps instead of one big step. When Bit DB19 is set to 0, the fast ramp function is disabled (see the Fast Ramp Mode section). Reserved Bits All reserved bits must be set to 0 for normal operation. TXDATA Trigger Delay When Bit DB23 is set to 0, there is no delay before the start of the ramp when using TXDATA to trigger a ramp. When Bit DB23 is set to 1, a delay is enabled before the start of the ramp if the delayed start is enabled via Bit DB15. Ramp Delay Fast Lock When Bit DB18 is set to 1, the ramp delay fast lock function is enabled. When Bit DB18 is set to 0, this function is disabled. Triangular Delay Ramp Delay When Bit DB22 is set to 1, a delay is enabled between each section of a triangular ramp, resulting in a clipped ramp. This setting works only for triangular ramps and when the ramp delay is activated. When Bit DB22 is set to 0, the delay between triangular ramps is disabled. When Bit DB17 is set to 1, the delay between ramps function is enabled. When Bit DB17 is set to 0, this function is disabled. Delay Clock Select When Bit DB16 is set to 0, the PFD clock is selected as the delay clock. When Bit DB16 is set to 1, PFD clock x CLK1 is selected as the delay clock. (CLK1 is set by Bits DB[14:3] in Register R2.) Single Full Triangle When Bit DB21 is set to 1, the single full triangle function is enabled. When Bit DB21 is set to 0, this function is disabled. To use the single full triangle function, Ramp Mode (Register 3, DB[11:10]) must be set to 0b11, Single Ramp Burst. For more information, see the Waveform Generation section. Delayed Start Enable When Bit DB15 is set to 1, the delayed start is enabled. When Bit DB15 is set to 0, the delayed start is disabled. 12-Bit Delay Start Word TXDATA Trigger Bits DB[14:3] determine the delay start word. The delay start word affects the duration of the ramp start delay. DB31 DB30 DB29 DB28 DB27 DB26 DB25 DB24 DB23 DB22 DB21 DB20 DB19 DB18 DB17 DB16 DB15 DB14 DB13 DB12 DB11 DB10 DB9 0 0 0 0 0 0 0 0 0 TD1 TD1 TRI DELAY 0 DISABLED 1 ENABLED 0 TXDATA TRIGGER DELAY 0 DISABLED 1 ENABLED ST1 TR1 FR1 0 RD1 DC1 DSE1 DS12 DS11 DS10 DS9 0 0 RAMP DELAY FL DISABLED 1 ENABLED 0 DISABLED 1 ENABLED 1 TR1 TXDATA TRIGGER DB7 DB6 DB5 DB4 DB3 DS6 DS5 DS4 DS3 DS2 DS1 C3(1) C2(1) C1(1) DS2 DS1 ... 0 0 0 0 0 ... 0 1 1 0 0 ... 1 0 2 0 0 ... 1 1 3 . . ... . . . . . ... . . . . . ... . . . 1 1 ... 0 0 4092 RAMP DELAY 1 1 ... 0 1 4093 DC1 0 1 RD1 DB8 ... 0 1 ENABLED DS7 0 DSE1 DEL START EN ST1 SING FULL TRI 0 DISABLED DS8 0 DS12 DS11 FR1 FAST RAMP DISABLED ENABLED DEL CLK SEL PFD CLK PFD CLK x CLK1 DISABLED 0 DISABLED 1 1 ... 1 0 4094 1 ENABLED 1 ENABLED 1 1 ... 1 1 4095 Figure 32. Delay Register (R7) Map DB2 DB1 DB0 DELAY START WORD 0 Rev. E | Page 24 of 36 CONTROL BITS 12-BIT DELAY START WORD 10849-027 DEL START EN DEL CLK SEL RAMP DELAY RAMP DELAY FL FAST RAMP TXDATA TRIGGER SING FULL TRI RESERVED TRI DELAY TXDATA TRIGGER DELAY When Bit DB20 is set to 1, a logic high on TXDATA activates the ramp. When Bit DB20 is set to 0, this function is disabled. Data Sheet ADF4159 APPLICATIONS INFORMATION INITIALIZATION SEQUENCE REFERENCE DOUBLER After powering up the ADF4159, initialize the part by programming the registers in the following sequence: The on-chip reference doubler allows the input reference signal to be doubled. This doubling is useful for increasing the PFD comparison frequency. Doubling the PFD frequency usually improves the noise performance of the system by 3 dB. It is important to note that the PFD cannot be operated above 110 MHz due to a limitation in the speed of the - circuit of the N divider. 1. 2. 3. 4. 5. 6. 7. 8. Delay register (R7). Step register (R6). Load the step register twice, first with STEP SEL = 0 and then with STEP SEL = 1. Deviation register (R5). Load the deviation register twice, first with DEV SEL = 0 and then with DEV SEL = 1. Clock register (R4). Load the clock register twice, first with CLK DIV SEL = 0 and then with CLK DIV SEL = 1. Function register (R3). R divider register (R2). LSB FRAC register (R1). FRAC/INT register (R0). CYCLE SLIP REDUCTION FOR FASTER LOCK TIMES In fast locking applications, a wide loop filter bandwidth is required for fast frequency acquisition, resulting in increased integrated phase noise and reduced spur attenuation. Using cycle slip reduction, the loop bandwidth can be kept narrow to reduce integrated phase noise and attenuate spurs while still realizing fast lock times. RF SYNTHESIZER WORKED EXAMPLE Cycle Slips The following equation governs how the synthesizer must be programmed. Cycle slips occur in integer-N/fractional-N synthesizers when the loop bandwidth is narrow compared with the PFD frequency. The phase error at the PFD inputs accumulates too fast for the PLL to correct, and the charge pump temporarily pumps in the wrong direction, slowing down the lock time dramatically. The ADF4159 contains a cycle slip reduction circuit to extend the linear range of the PFD, allowing faster lock times without loop filter changes. RFOUT = (INT + (FRAC/225)) x fPFD (4) where: RFOUT is the RF frequency output. INT is the integer division factor. FRAC is the fractionality. The PFD frequency (fPFD) equation is fPFD = REFIN x [(1 + D)/(R x (1 + T))] (5) where: REFIN is the reference frequency input. D is the RF REFIN doubler bit, Bit DB20 in Register R2 (0 or 1). R is the RF reference division factor (1 to 32). T is the reference divide-by-2 bit, Bit DB21 in Register R2 (0 or 1). For example, in a system where a 12.102 GHz RF frequency output (RFOUT) is required and a 100 MHz reference frequency input (REFIN) is available, the frequency resolution is fRES = REFIN/225 (6) fRES = 100 MHz/225 = 2.98 Hz If the phase error increases again to a point where another cycle slip is likely, the ADF4159 turns on another charge pump cell. This continues until the ADF4159 detects that the VCO frequency has exceeded the desired frequency. It then begins to turn off the extra charge pump cells one by one until they are all turned off and the frequency is settled. Up to seven extra charge pump cells can be turned on. In most applications, seven cells is enough to eliminate cycle slips altogether, giving much faster lock times. From Equation 5, fPFD = [100 MHz x (1 + 0)/1] = 100 MHz 12.102 GHz = 100 MHz x (N + FRAC/225) Calculating the N and FRAC values, N = int(RFOUT/fPFD) = 121 FRAC = FMSB x 213 + FLSB FMSB = int(((RFOUT/fPFD) - N) x 212) = 81 FLSB = int(((((RFOUT/fPFD) - N) x 212) - FMSB) x 213) = 7536 where: FMSB is the 12-bit MSB FRAC value in Register R0. FLSB is the 13-bit LSB FRAC value in Register R1. int() makes an integer of the argument in parentheses. When the ADF4159 detects that a cycle slip is about to occur, it turns on an extra charge pump current cell. This outputs a constant current to the loop filter or removes a constant current from the loop filter (depending on whether the VCO tuning voltage must increase or decrease to acquire the new frequency). The effect is that the linear range of the PFD is increased. Stability is maintained because the current is constant and is not a pulsed current. When Bit DB28 in the R divider register (Register R2) is set to 1, cycle slip reduction is enabled. Note that a 45% to 55% duty cycle is needed on the signal at the PFD in order for CSR to operate correctly. The reference divide-by-2 flip-flop can help to provide a 50% duty cycle at the PFD. For example, if a 100 MHz reference frequency is available and the user wants to run the PFD at 10 MHz, setting the R divide factor to 10 results in a 10 MHz PFD signal that is not 50% duty cycle. By setting the R divide factor to 5 and enabling the reference divide-by-2 bit, a 50% duty cycle 10 MHz signal can be achieved. Rev. E | Page 25 of 36 ADF4159 Data Sheet Note that the cycle slip reduction feature can only be operated when the phase detector polarity setting is positive (Bit DB6 in Register R3 is set to 1). It cannot be used if the phase detector polarity is negative. MODULATION The ADF4159 can operate in frequency shift keying (FSK) or phase shift keying (PSK) mode. The ADF4159 is capable of generating five types of waveforms in the frequency domain: single ramp burst, single triangular burst, single sawtooth burst, continuous sawtooth ramp, and continuous triangular ramp. Figure 33 through Figure 37 show the types of waveforms available. FSK is implemented by configuring the ADF4159 N divider for the center frequency and then toggling the TXDATA pin. The deviation from the center frequency is set by fDEV = (fPFD/225) x (DEV x 2DEV_OFFSET) (7) The ADF4159 implements fDEV by incrementing or decrementing the configured N divider value by DEV x 2DEV_OFFSET. TIME Figure 33. Single Ramp Burst FREQUENCY where: fPFD is the PFD frequency. DEV is a 16-bit word (Bits DB[18:3] in Register R5). DEV_OFFSET is a 4-bit word (Bits DB[22:19] in Register R5). 10849-028 FREQUENCY Frequency Shift Keying (FSK) WAVEFORM GENERATION In this example, an FSK system operates at 5.8 GHz with a 25 MHz fPFD, requiring 250 kHz deviation (fDEV). 10849-029 FSK Settings Worked Example TIME Figure 34. Single Triangular Burst Rearrange Equation 7 as follows: (DEV x 2DEV_OFFSET) = 250 kHz/(25 MHz/225) (DEV x 2DEV_OFFSET) = 335,544.32 If DEV_OFFSET is set to 6, DEV = 335,544.32/(26) = 5242.88 5243 TIME 10849-030 FREQUENCY (DEV x 2DEV_OFFSET) = fDEV/(fPFD/225) Figure 35. Single Sawtooth Burst Phase Shift Keying (PSK) When the ADF4159 is configured for PSK mode, the output phase of the ADF4159 is equal to (Phase Value x 360)/212 TIME 10849-031 Toggling the TXDATA pin causes the frequency to hop between 250 kHz from the programmed center frequency. FREQUENCY Due to the rounding of DEV, fDEV = 250.005722 kHz. Figure 36. Continuous Sawtooth Ramp TIME Figure 37. Continuous Triangular Ramp Rev. E | Page 26 of 36 10849-032 For example, if the phase value is 1024, a logic high on the TXDATA pin results in a 90 increase of the output phase. A logic low on the TXDATA pin results in a 90 decrease of the output phase. The polarity can be inverted by negating the phase value. FREQUENCY The phase value is set in Register 1, Bits DB[14:3]. The PSK modulation is controlled by the TXDATA pin. Data Sheet ADF4159 WAVEFORM DEVIATIONS AND TIMING SINGLE TRIANGULAR BURST Figure 38 shows a version of a ramp. The single triangular burst is similar to the single ramp burst. However, when the steps are completed, the ADF4159 begins to decrement the N divider value by DEV x 2DEV_OFFSET on each timeout interval. TIMER SINGLE SAWTOOTH BURST 10849-033 FREQUENCY fDEV TIME Figure 38. Waveform Timing Frequency deviation Timeout interval Number of steps TRIANGULAR RAMP Frequency Deviation The frequency deviation for each frequency hop is set by fDEV = (fPFD/225) x (DEV x 2DEV_OFFSET) (7) where: fPFD is the PFD frequency. DEV is a 16-bit word (Bits DB[18:3] in Register R5). DEV_OFFSET is a 4-bit word (Bits DB[22:19] in Register R5). Timeout Interval The time between each frequency hop is set by Timer = CLK1 x CLK2 x (1/fPFD) SAWTOOTH RAMP The sawtooth ramp is a repeated version of the single sawtooth burst. The waveform is repeated until the ramp is disabled. The key parameters that define a ramp are * * * In the single sawtooth burst, the N divider value is reset to its initial value on the next timeout interval after the number of steps has taken place. The ADF4159 retains this N divider value. (8) where: CLK1 and CLK2 are the 12-bit clock values (12-bit CLK1 divider in Register R2 and 12-bit CLK2 divider in Register R4). Bits DB[20:19] in Register R4 must be set to 11 for ramp divider. fPFD is the PFD frequency. Either CLK1 or CLK2 must be greater than 1, that is, CLK1 = CLK2 = 1 is not allowed. The triangular ramp is a repeated version of the single triangular burst. However, when the steps are completed, the ADF4159 begins to decrement the N divider value by DEV x 2DEV_OFFSET on each timeout interval. When the number of steps has again been completed, the part reverts to incrementing the N divider value. Repeating this pattern creates a triangular waveform. The waveform is repeated until the ramp is disabled. FMCW RADAR RAMP SETTINGS WORKED EXAMPLE This example describes a frequency modulated continuous wave (FMCW) radar system that requires the RF LO to use a sawtooth ramp over a 50 MHz range every 2 ms. The PFD frequency is 25 MHz, and the RF output range is 5800 MHz to 5850 MHz. The frequency deviation for each hop in the ramp is set to ~250 kHz. The frequency resolution of the ADF4159 is calculated as follows: fRES = fPFD/225 (9) Using Equation 9, fRES is calculated as follows: fRES = 25 MHz/225 = 0.745 Hz DEV_OFFSET is calculated after rearranging Equation 7. Number of Steps A 20-bit step value (Bits DB[22:3] in Register R6) defines the number of frequency hops that take place. The INT value cannot be incremented by more than 28 = 256 from its starting value. DEV_OFFSET = log2(fDEV/(fRES x DEVMAX)) Expressed in log10(x), Equation 10 can be rearranged into the following equation: SINGLE RAMP BURST DEV_OFFSET = log10(fDEV/(fRES x DEVMAX))/log10(2) The most basic waveform is the single ramp burst. All other waveforms are variations of this waveform. In the single ramp burst, the ADF4159 is locked to the frequency defined in the FRAC/INT register (R0). When the ramp mode is enabled, the ADF4159 increments the N divider value by DEV x 2DEV_OFFSET, causing a frequency shift, fDEV, on each timer interval. This shift is repeated until the set number of steps has taken place. The ADF4159 then retains the final N divider value. (10) (11) where: fDEV is the frequency deviation. DEVMAX = 215 (maximum value of the deviation word). DEV_OFFSET is a 4-bit word. Using Equation 11, DEV_OFFSET is calculated as follows: DEV_OFFSET = log10(250 kHz/(0.745 Hz x 215))/log10(2) = 3.356 After rounding, DEV_OFFSET = 4. Rev. E | Page 27 of 36 ADF4159 Data Sheet fDEV_RES = fRES x 2DEV_OFFSET (12) fDEV_RES = 0.745 Hz x 2 = 11.92 Hz 4 To calculate the DEV word, use Equation 13. DEV = fDEV/(fRES x 2DEV_OFFSET) DEV = (13) 250 kH z = 20,971.52 25 MHz 4 x2 2 25 OTHER WAVEFORMS Dual Ramps with Different Ramp Rates The ADF4159 can be configured for two ramps with different step and deviation settings. It also allows the ramp rate to be reprogrammed while another ramp is running. Example In this example, the PLL is locked to 5790 MHz and fPFD = 25 MHz. Two ramps are configured, as follows: * Rounding this value to 20,972 and recalculating using Equation 7 to obtain the actual deviation frequency, fDEV, thus produces the following: fDEV = (25 MHz/225) x (20,972 x 24) = 250.006 kHz The number of fDEV steps required to cover the 50 MHz range is 50 MHz/250.006 kHz = 200. To cover the 50 MHz range in 2 ms, the ADF4159 must hop every 2 ms/200 = 10 s. * To enable the two ramp rates, follow these steps: 1. 2. Rearrange Equation 8 to set the timer value (and set CLK2 to 1): To summarize the settings, * ACTIVATING THE RAMP After setting all required parameters, the ramp must be activated by choosing the desired type of ramp (Bits DB[11:10] in Register R3) and starting the ramp (Bit DB31 = 1 in Register R0). 3. Register R5: set Bit DB23 = 0, Bits DB[18:3] = 16,777, and Bits DB[22:19] = 3 Register R6: set Bit DB23 = 0 and Bits DB[22:3] = 100 Program the ramp rate for Ramp 2 by setting the following values: * * Register R5: set Bit DB23 = 1, Bits DB[18:3] = 20,972, and Bits DB[22:19] = 3 Register R6: set Bit DB23 = 1 and Bits DB[22:3] = 80 Figure 39 shows the resulting ramp with two ramp rates. To activate the ramp, see the Activating the Ramp section. SWEEP RATE SET BY OTHER REGISTER FREQUENCY DEV = 20,972 Number of steps = 200 CLK1 = 250 CLK2 = 1 (Bits DB[20:19] = 11, ramp divider, in Register R4) Using these settings, program the ADF4159 to a center frequency of 5800 MHz and enable the sawtooth ramp to produce the required waveform. If a triangular ramp is used with the same settings, the ADF4159 sweeps from 5800 MHz to 5850 MHz and back down again, taking 4 ms for the entire sweep. Ramp Programming Sequence SWEEP RATE SET BY ONE REGISTER TIME The setting of parameters described in the FMCW Radar Ramp Settings Worked Example section and the activation of the ramp described in the Activating the Ramp section must be completed in the following register write order: 1. 2. 3. 4. 5. 6. 7. 8. Activate the dual ramp rates mode by setting Bit DB24 in Register R5 to 1. Program the ramp rate for Ramp 1 by setting the following values: * CLK1 = Timer x fPFD/CLK2 = 10 s x 25 MHz/1 = 250 * * * * Ramp 1 jumps 100 steps; each step lasts 10 s and has a frequency deviation of 100 kHz. Ramp 2 jumps 80 steps; each step lasts 10 s and has a frequency deviation of 125 kHz. Delay register (R7) Step register (R6) Deviation register (R5) Clock register (R4) Function register (R3) R divider register (R2) LSB FRAC register (R1) FRAC/INT register (R0) Rev. E | Page 28 of 36 Figure 39. Dual Ramp with Two Sweep Rates 10849-134 From DEV_OFFSET, the resolution of the frequency deviation can be calculated as follows: Data Sheet ADF4159 Ramp Mode with Superimposed FSK Signal Delayed Start In traditional approaches, FMCW radars use either linear frequency modulation (LFM) or FSK modulation. Used separately, these modulations introduce ambiguity between measured distance and velocity, especially in multitarget situations. To overcome this issue and enable unambiguous (distance and velocity) multitarget detection, use a ramp with FSK superimposed on it. A delayed start can be used with two different parts to control the start time. Figure 41 shows the theory of delayed start. * RAMP WITH DELAYED START TIME Figure 41. Delayed Start of Sawtooth Ramp The number of steps is set to 100; each step lasts 10 s and has a deviation of 100 kHz. The FSK signal is 25 kHz. * Example For example, to program a delayed start with two different parts to control the start time, follow these steps: To enable ramp mode with FSK superimposed on it, follow these steps: 1. 2. 3. 1. Set Bit DB23 in Register R5 and Bit DB23 in Register R6 to 0. Program the ramp as described in the FMCW Radar Ramp Settings Worked Example section. Program FSK on the ramp to 25 kHz by setting the bits in Register R5 as follows: * * * * DB[18:3] = 4194 (deviation word) DB[22:19] = 3 (deviation offset word) DB23 = 1 (deviation word for FSK on the ramp) DB25 = 1 (ramp with FSK enabled) 2. Enable the delayed start of ramp option by setting Bit DB15 in Register R7 to 1. Delay the ramp on the first part by 5 s by setting Bit DB16 in Register R7 to 0 and setting the 12-bit delay start word (Bits DB[14:3] in Register R7) to 125 (fPFD = 25 MHz). The delay is calculated as follows: Delay = tPFD x Delay Start Word Delay = 40 ns x 125 = 5 s 3. Figure 40 shows an example of a ramp with FSK superimposed on it. To activate the ramp, see the Activating the Ramp section. Delay the ramp on the second part by 125 s by setting Bit DB16 in Register R7 to 1 and setting the 12-bit delay start word (Bits DB[14:3] in Register R7) to 125. The delay is calculated as follows: Delay = tPFD x CLK1 x Delay Start Word Delay = 40 ns x 25 x 125 = 125 s 0 TIME RAMP END 10849-135 LFMSTEP = FREQUENCY SWEEP/NUMBER OF STEPS FREQUENCY SWEEP FREQUENCY To activate the ramp, see the Activating the Ramp section. FSK SHIFT 10849-034 In this example, the PLL is locked to 5790 MHz and fPFD = 25 MHz. The ramp with superimposed FSK is configured as follows: FREQUENCY Example RAMP WITHOUT DELAYED START Figure 40. Combined FSK and LFM Waveform Rev. E | Page 29 of 36 ADF4159 Data Sheet Delay Between Ramps It is also possible to activate fast lock operation for the first period of delay by setting Bit DB18 in Register R7 to 1. This feature is useful for sawtooth ramps to mitigate the frequency overshoot on the transition from one sawtooth to the next. The ADF4159 can be configured to add a delay between bursts in ramps. Figure 42, Figure 43, and Figure 44 show a delay between ramps in sawtooth, triangular, and clipped triangular mode, respectively. To activate the ramp, see the Activating the Ramp section. Dual Ramp Rates Mode with Delay This mode combines the modes described in the Dual Ramps with Different Ramp Rates section and the Delay Between Ramps section (see Figure 45). Figure 42. Delay Between Ramps for Sawtooth Mode 10849-140 TIME FREQUENCY 10849-035 FREQUENCY DELAY FREQUENCY TIME Figure 45. Dual Ramp Rates Mode with Delay 10849-036 To enable this configuration, TIME Figure 43. Delay Between Ramps for Triangular Mode 1. Program the two ramp rates mode as described in the Dual Ramps with Different Ramp Rates section. Program the delay as described in the Delay Between Ramps section. 2. Parabolic (Nonlinear) Ramp Mode The ADF4159 is capable of generating a parabolic ramp (see Figure 46). Figure 44. Delay Between Ramps for Clipped Triangular Mode Example For example, to add a delay between bursts in a ramp, follow these steps: 1. 2. Enable the delay between ramps option by setting Bit DB17 in Register R7 to 1. Delay the ramp by 5 s by setting Bit DB16 in Register R7 to 0 and setting the 12-bit delay start word (Bits DB[14:3] in Register R7) to 125 (fPFD = 25 MHz). The delay is calculated as follows: Delay = tPFD x Delay Start Word Delay = 40 ns x 125 = 5 s If a longer delay is needed, for example, 125 s, set Bit DB16 in Register R7 to 1, and set the 12-bit delay start word (Bits DB[14:3] in Register R7) to 125. The delay is calculated as follows: Delay = tPFD x CLK1 x Delay Start Word Delay = 40 ns x 25 x 125 = 125 s TIME 10849-141 TIME FREQUENCY 10849-037 FREQUENCY DELAY Figure 46. Parabolic Ramp The output frequency is generated according to the following equation: fOUT(n + 1) = fOUT(n) + n x fDEV (14) where: fOUT is the output frequency. n is the step number. fDEV is the frequency deviation. Example This example describes how to set up and use the parabolic ramp mode with the following parameters: * * * * Rev. E | Page 30 of 36 fOUT = 5790 MHz fDEV = 100 kHz Number of steps = 50 Duration of a single step = 10 s Data Sheet ADF4159 4. Configure one of the following ramp modes: * Continuous triangular ramp (set Register R3, Bits DB[11:10] to 01). Single ramp burst (set Register R3, Bits DB[11:10] to 11). b. For the continuous triangular ramp, the generated frequency range is calculated as follows: f = fDEV x (Number of Steps + 2) x (Number of Steps + 1)/2 = 132.6 MHz For the single ramp burst, the generated frequency range is calculated as follows: f = fDEV x (Number of Steps + 1) x Number of Steps/2 = 127.5 MHz 2. Set the timer as described for the linear ramps in the Timeout Interval section. Activate the parabolic ramp by setting Bit DB28 in Register R5 to 1. Set the counter reset (Bit DB3 in Register R3) to 1 and then set it to 0. 3. 4. To activate the ramp, see the Activating the Ramp section. Fast Ramp Mode The ADF4159 is capable of generating a fast ramp. The fast ramp is a triangular ramp with two different slopes (see Figure 47). The number of steps, time per step, and deviation per step are programmable for both the up and down ramps. 5. Calculate and program the timer, DEV, DEV_OFFSET, and the step word as described in the FMCW Radar Ramp Settings Worked Example section. Start the ramp by setting Bit DB31 = 1 in Register R0. Note that the total frequency change of the up and down ramps must be equal for stability. RAMP COMPLETE SIGNAL TO MUXOUT Figure 48 shows the ramp complete signal on MUXOUT. FREQUENCY * TIME VOLTAGE 1. Program the down ramp as follows. a. Set Bit DB6 in Register R4 (CLK DIV SEL), Bit DB23 in Register R5 (DEV SEL), and Bit DB23 in Register R6 (STEP SEL) to 1 for Ramp 2. TIME 10849-039 To set up the parabolic ramp mode, follow these steps: Figure 48. Ramp Complete Signal on MUXOUT To activate this function, set Bits DB[30:27] in Register R0 to 1111, and set Bits DB[25:21] in Register R4 to 00011. EXTERNAL CONTROL OF RAMP STEPS RFOUT To activate the fast ramp waveform, follow these steps: 2. 3. Select the continuous triangular waveform by setting Bits DB[11:10] in Register R3 to 01. Enable the fast ramp by setting Bit DB19 in Register R7 to 1. Program the up ramp as follows. a. Set Bit DB6 in Register R4 (CLK DIV SEL), Bit DB23 in Register R5 (DEV SEL), and Bit DB23 in Register R6 (STEP SEL) to 0 for Ramp 1. b. TIME VOLTAGE 1. Calculate and program the timer, DEV, DEV_OFFSET, and the step word as described in the FMCW Radar Ramp Settings Worked Example section. Rev. E | Page 31 of 36 TXDATA TIME Figure 49. External Control of Ramp Steps 10849-148 Figure 47. Fast Ramp Mode FREQUENCY TIME 10849-038 FREQUENCY The internal ramp clock can be bypassed and each step can be triggered by a pulse on the TXDATA pin. This allows for more transparent control of each step. Enable this feature by setting Bit DB29 in Register R5 to 1. ADF4159 Data Sheet INTERRUPT MODES AND FREQUENCY READBACK When an interrupt takes place, the data, consisting of the INT and FRAC values, can be read back via MUXOUT. The data comprises 37 bits: 12 bits represent the INT value and 25 bits represent the FRAC value. Figure 51 shows how single bits are read back. Interrupt modes are triggered from the rising edge of TXDATA. To activate this function, set Bits DB[30:27] in Register R0 to 1111, and set Bits DB[25:21] in Register R4 to 00010. To select and enable the interrupt mode, set Bits DB[27:26] in Register R5 as shown in Table 8. A ramp must be active for readback to work. DATA CLOCKED OUT ON POSITIVE EDGE OF CLK AND READ ON NEGATIVE EDGE OF CLK READBACK WORD (37 BITS) 0 0001 1100 1111 0110 0010 0011 1010 0111 1000 (0x1CF623A78) Table 8. Interrupt Modes (Register R5) TXDATA Interrupt Mode Interrupt is off Interrupt on TXDATA, sweep continues Interrupt on TXDATA, sweep stops LE CLK MUXOUT Figure 50 shows the theory of frequency readback. FREQUENCY FREQUENCY AT WHICH INTERRUPT TOOK PLACE 1 2 25-BIT FRAC WORD 1 0110 0010 0011 1010 0111 1000 0x1623A78 23,214,712 RF = fPFD x (231 + 23,214,712/2 25) = 1.7922963GHz Figure 51. Reading Back Single Bits to Determine the Output Frequency at the Moment of Interrupt For continuous frequency readback, the following sequence must be used (see Figure 52). TIME TIME OF INTERRUPT 1. 2. 3. 4. 5. 6. 7. 8. 1. SWEEP CONTINUES MODE 2. SWEEP STOPS MODE INTERRUPT SIGNAL LOGIC HIGH 10849-040 LOGIC LOW TIME Register 0 write LE high Pulse on TXDATA Frequency readback Pulse on TXDATA Register R4 write Frequency readback Pulse on TXDATA Figure 52 shows the continuous frequency readback sequence. Figure 50. Interrupt and Frequency Readback TXDATA 32 CLK PULSES 37 CLK PULSES 32 CLK PULSES 37 CLK PULSES 32 CLK PULSES 37 CLK PULSES CLK FREQUENCY READBACK FREQUENCY READBACK FREQUENCY READBACK MUXOUT R0 WRITE R4 WRITE R4 WRITE DATA LE 10849-042 LOGIC LEVEL LSB MSB 12-BIT INTEGER WORD 0000 1110 0111 0x0E7 231 10849-041 Bits DB[27:26] 00 01 11 Figure 52. Continuous Frequency Readback Rev. E | Page 32 of 36 Data Sheet ADF4159 FAST LOCK MODE Fast Lock Loop Filter Topology The ADF4159 can operate in fast lock mode. In this mode, the charge pump current is boosted and additional resistors are connected to maintain the stability of the loop. To use fast lock mode, an extra connection from the PLL to the loop filter is needed. The damping resistor in the loop filter must be reduced to 1/4 of its value in wide bandwidth mode. This reduction is required because the charge pump current is increased by 16 in wide bandwidth mode, and stability must be ensured. Fast Lock Timer and Register Sequences When fast lock mode is enabled (Register R4, DB[20:19]), after a write to Register R0, the PLL operates in a wide bandwidth mode for a selected amount of time. Before fast lock is enabled, the initialization sequence must be performed after the part is first powered up (see the Initialization Sequence section). The time in bandwidth mode is set by: CLK1 x CLK2 / fPFD = Time in wide bandwidth To further enhance stability and mitigate frequency overshoot during a frequency change in wide bandwidth mode, Resistor R3 is connected (see Figure 53). During fast lock, the SW1 pin is shorted to ground, and the SW2 pin is connected to CP (set Bits DB[20:19] in Register R4 to 01 for fast lock divider). The following two topologies can be used: where: * CLK1 = Register R2, DB[14:3]. CLK2 = Register R4, DB[18:7]. fPFD = the PFD frequency. * Note that the fast lock feature does not work in ramp mode. Fast Lock Example In this example, the PLL has fPFD of 100 MHz and requires being in wide bandwidth mode for 12 s. Divide the damping resistor (R1) into two values (R1 and R1A) that have a ratio of 1:3 (see Figure 53). Connect an extra resistor (R1A) directly from SW1 (see Figure 54). The extra resistor must be selected such that the parallel combination of an extra resistor and the damping resistor (R1) is reduced to 1/4 of the original value of R1. For both topologies, the ratio R3:R2 must equal 1:4. R3 SW2 R2 VCO CP CLK1 x CLK2 / fPFD = 12 s C1 ADF4159 CLK1 x CLK2 = (12 x 10-6)(100 x 106) = 1200 C2 C3 R1 Therefore, CLK1 = 12 and CLK2 = 100, which results in 12 s. SW1 10849-047 R1A Figure 53. Fast Lock Loop Filter Topology 1 R3 SW2 R2 VCO CP C1 ADF4159 C2 C3 R1A R1 10849-048 SW1 Figure 54. Fast Lock Loop Filter Topology 2 For more fast lock topologies, see ADIsimPLLTM. Rev. E | Page 33 of 36 ADF4159 Data Sheet SPUR MECHANISMS Low Frequency Applications The fractional interpolator in the ADF4159 is a third-order - modulator with a 25-bit fixed modulus (MOD). The - modulator is clocked at the PFD reference rate (fPFD), which allows PLL output frequencies to be synthesized at a channel step resolution of fPFD/CLK1. This section describes the various spur mechanisms that are possible with fractional-N synthesizers and how they affect the ADF4159. The specification of the RF input is 0.5 GHz minimum; however, RF frequencies lower than 0.5 GHz can be used if the minimum slew rate specification of 400 V/s is met. An appropriate driver-- for example, the ADCMP553--can be used to accelerate the edge transitions of the RF signal before it is fed back to the ADF4159 RF input. Fractional Spurs A filter design and analysis program is available to help the user implement PLL design. Visit http://www.analog.com/pll to download the free ADIsimPLLTM software. This software designs, simulates, and analyzes the entire PLL frequency domain and time domain response. Various passive and active filter architectures are allowed. In most fractional synthesizers, fractional spurs can appear at the set channel spacing of the synthesizer. In the ADF4159, these spurs do not appear. The high value of the fixed modulus in the ADF4159 makes the - modulator quantization error spectrum look like broadband noise, effectively spreading the fractional spurs into noise. Integer Boundary Spurs Interactions between the RF VCO frequency and the PFD frequency can lead to spurs known as integer boundary spurs. When these frequencies are not integer related (which is the purpose of a fractional-N synthesizer), spur sidebands appear on the VCO output spectrum at an offset frequency that corresponds to the beat note, or difference frequency, between an integer multiple of the PFD and the VCO frequency. These spurs are called integer boundary spurs because they are more noticeable on channels close to integer multiples of the PFD, where the difference frequency can be inside the loop bandwidth. These spurs are attenuated by the loop filter on channels far from integer multiples of the PFD. Reference Spurs Reference spurs are generally not a problem in fractional-N synthesizers because the reference offset is far outside the loop bandwidth. However, any reference feedthrough mechanism that bypasses the loop can cause a problem. One such mechanism is the feedthrough of low levels of on-chip reference switching noise out through the RFINx pins back to the VCO, resulting in reference spur levels as high as -90 dBc. Take care in the PCB layout to ensure that the VCO is well separated from the input reference to avoid a possible feedthrough path on the board. FILTER DESIGN USING ADIsimPLL PCB DESIGN GUIDELINES FOR THE CHIP SCALE PACKAGE The lands on the chip scale package (CP-24-10) are rectangular. The printed circuit board (PCB) pad for these lands must be 0.1 mm longer than the package land length and 0.05 mm wider than the package land width. Center the land on the pad to ensure that the solder joint size is maximized. The bottom of the chip scale package has a central exposed thermal pad. The thermal pad on the PCB must be at least as large as this exposed pad. On the PCB, there must be a clearance of at least 0.25 mm between the thermal pad and the inner edges of the pad pattern to ensure that shorting is avoided. Thermal vias can be used on the PCB thermal pad to improve the thermal performance of the package. If vias are used, incorporate them into the thermal pad at the 1.2 mm pitch grid. The via diameter must be between 0.3 mm and 0.33 mm, and the via barrel must be plated with 1 ounce of copper to plug the via. Connect the PCB thermal pad to AGND. Rev. E | Page 34 of 36 Data Sheet ADF4159 APPLICATION OF THE ADF4159 IN FMCW RADAR The PLL solution also has advantages over another method for generating FMCW ramps: a DAC driving the VCO directly; this method suffers from nonlinearities of the VCO tuning characteristics, requiring compensation. The PLL method produces highly linear ramps without the need for calibration. Figure 55 shows the application of the ADF4159 in a frequency modulated continuous wave (FMCW) radar system. In the FMCW radar system, the ADF4159 is used to generate the sawtooth or triangle ramps that are necessary for this type of radar to operate. Traditionally, the PLL was driven directly by a direct digital synthesizer (DDS) to generate the required type of waveform. Due to the waveform generating mechanism that is implemented on the ADF4159, a DDS is no longer needed, which reduces cost. NO DDS REQUIRED WITH ADF4159 LINEAR FREQUENCY SWEEP REFERENCE OSCILLATOR VCO ADF4159 x2 Tx ANTENNA PA MULT x2 Rx ANTENNAS MICROCONTROLLER DSP 16 BITS ADSP-BF531 BUS CAN/FLEXRAY BASEBAND HPF ADC 10 BITS TO 12 BITS MUX MIXER RANGE COMPENSATION FREQUENCY MODULATED CONTINUOUS WAVE LONG RANGE RADAR Figure 55. FMCW Radar with the ADF4159 Rev. E | Page 35 of 36 : . . 10849-043 AD8283 ADF4159 Data Sheet OUTLINE DIMENSIONS 0.30 0.25 0.20 0.50 BSC PIN 1 INDICATOR 24 19 18 1 EXPOSED PAD TOP VIEW 0.80 0.75 0.70 0.50 0.40 0.30 13 12 2.20 2.10 SQ 2.00 6 7 0.25 MIN BOTTOM VIEW 0.05 MAX 0.02 NOM FOR PROPER CONNECTION OF THE EXPOSED PAD, REFER TO THE PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SECTION OF THIS DATA SHEET. COPLANARITY 0.08 SEATING PLANE 0.20 REF COMPLIANT TO JEDEC STANDARDS MO-220-WGGD-8. 06-11-2012-A PIN 1 INDICATOR 4.10 4.00 SQ 3.90 Figure 56. 24-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 4 mm x 4 mm Body, Very Very Thin Quad (CP-24-10) Dimensions shown in millimeters ORDERING GUIDE Model1, 2 ADF4159CCPZ ADF4159CCPZ-RL7 ADF4159WCCPZ ADF4159WCCPZ-RL7 EV-ADF4159EB1Z Temperature Range -40C to +125C -40C to +125C -40C to +125C -40C to +125C EV-ADF4159EB3Z 1 2 Package Description 24-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 24-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 24-Lead Lead Frame Chip Scale Package [LFCSP_WQ] 24-Lead Lead Frame Chip Scale Package [LFCSP_WQ] Evaluation Board (12 GHz VCO, 284 kHz Loop Bandwidth, 48 Phase Margin) Evaluation Board (Set up for External, SMA Connected VCO Board; Filter Unpopulated) Package Option CP-24-10 CP-24-10 CP-24-10 CP-24-10 Z = RoHS Compliant Part. W = Qualified for automotive applications. AUTOMOTIVE PRODUCTS The ADF4159W models are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. Note that these automotive models may have specifications that differ from the commercial models; therefore, designers should review the Specifications section of this data sheet carefully. Only the automotive grade products shown are available for use in automotive applications. Contact your local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for these models. (c)2013-2014 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D10849-0-7/14(E) Rev. E | Page 36 of 36 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Analog Devices Inc.: ADF4159CCPZ ADF4159CCPZ-RL7 EV-ADF4159EB3Z EV-ADF4159EB1Z