ADRF6720ACPZ-R7

Wideband Quadrature Modulator with Integrated Fractional-N PLL and VCOs ADRF6720 Data Sheet FEATURES GENERAL DESCRIPTION I/Q modulator with integrated fractional-N PLL RF output frequency range: 700 MHz to 3000 MHz Internal LO frequency range: 356.25 MHz to 2855 MHz Output P1dB: 12.2 dBm at 2140 MHz Output IP3: 32.6 dBm at 2140 MHz Carrier feedthrough: −40.3 dBm at 2140 MHz Sideband suppression: −37.6 dBc at 2140 MHz Noise floor: −157.9 dBm/Hz at 2140 MHz Baseband 1 dB modulation bandwidth: >1000 MHz Baseband input bias level: 0.5 V Power supply: 3.3 V/425 mA Integrated RF tunable balun allowing single-ended RF output Multicore integrated VCOs HD3/IP3 optimization Sideband suppression and carrier feedthrough optimization High-side/low-side LO injection Programmable via 3-wire serial port interface (SPI) 40-lead 6 mm × 6 mm LFCSP The ADRF6720 is a wideband quadrature modulator with an integrated synthesizer ideally suited for 3G and 4G communication systems. The ADRF6720 consists of a high linearity broadband modulator, an integrated fractional-N phase-locked loop (PLL), and four low phase noise multicore voltage controlled oscillators (VCOs). The ADRF6720 local oscillator (LO) signal can be generated internally via the on-chip integer-N and fractional-N synthesizers, or externally via a high frequency, low phase noise LO signal. The internal integrated synthesizer enables LO coverage from 356.25 MHz to 2855 MHz using the multicore VCOs. In the case of internal LO generation or external LO input, quadrature signals are generated with a divide-by-2 phase splitter. When the ADRF6720 is operated with an external 1 × LO input, a polyphase filter generates the quadrature inputs to the mixer. The ADRF6720 offers digital programmability for carrier feedthrough optimization, sideband suppression, HD3/IP3 optimization, and high-side or low-side LO injection. APPLICATIONS 2G/3G/4G/LTE broadband communication systems Microwave point-to-point radios Satellite modems Military/aerospace Instrumentation The ADRF6720 is fabricated using an advanced silicongermanium BiCMOS process. It is available in a 40-lead, RoHS-compliant, 6 mm × 6 mm LFCSP package with an exposed pad. Performance is specified over the −40°C to +85°C temperature range. FUNCTIONAL BLOCK DIAGRAM VPOSx 40 30 26 22 17 11 6 3 ADRF6720 V TO I I– 4 LO NULLING DAC LO NULLING DAC Q– 8 27 ENBL 24 RFOUT 18 LOOUT+ 19 LOOUT– 15 CS 14 SCLK 13 SDIO PHASE CORRECTION PHASE CORRECTION V TO I Q+ 9 REFIN 39 CP 36 VTUNE 32 LOIN– 33 LOIN+ 34 PLL QUAD DIVIDER POLYPHASE FILTER 2 5 7 10 16 20 23 25 29 37 38 LDO 2.5V LDO VCO 12 28 DECL1 DECL2 GND SERIAL PORT INTERFACE 31 DECL3 12134-001 I+ 35 Figure 1. Rev. 0 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. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 ©2014 Analog Devices, Inc. All rights reserved. Technical Support www.analog.com ADRF6720 Data Sheet TABLE OF CONTENTS Features .............................................................................................. 1 Baseband Inputs ......................................................................... 24 Applications ....................................................................................... 1 LO Input ...................................................................................... 24 General Description ......................................................................... 1 Loop Filter ................................................................................... 24 Revision History ............................................................................... 2 RF Output .................................................................................... 24 Specifications..................................................................................... 3 Applications Information .............................................................. 25 Timing Characteristics ................................................................ 7 DAC-to-I/Q Modulator Interfacing......................................... 25 Absolute Maximum Ratings ............................................................ 8 Baseband Bandwidth ................................................................. 25 Thermal Resistance ...................................................................... 8 Carrier Feedthrough Nulling .................................................... 26 ESD Caution .................................................................................. 8 Sideband Suppression Optimization ....................................... 26 Pin Configuration and Function Descriptions ............................. 9 Linearity ....................................................................................... 27 Typical Performance Characteristics ........................................... 11 LO Amplitude and Common Mode Voltage .......................... 27 Theory of Operation ...................................................................... 18 Layout ........................................................................................... 27 LO Generation Block.................................................................. 18 Characterization Setups ................................................................. 29 Baseband ...................................................................................... 21 Register Map ................................................................................... 31 Active Mixers .............................................................................. 21 Register Details ............................................................................... 32 Serial Port Interface .................................................................... 22 Outline Dimensions ....................................................................... 42 Basic Connections for Operation ................................................. 23 Ordering Guide .......................................................................... 42 Power Supply and Grounding ................................................... 23 REVISION HISTORY 4/14—Revision 0: Initial Version Rev. 0 | Page 2 of 44 Data Sheet ADRF6720 SPECIFICATIONS VPOSx = 3.3 V, TA = 25°C; baseband I/Q amplitude = 1 V p-p differential sine waves in quadrature with a 500 mV dc bias, unless otherwise noted. Table 1. Parameter OPERATING FREQUENCY RANGE RF OUTPUT = 940 MHz Output Power, POUT Modulator Voltage Gain Output P1dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Output IP2 Output IP3 Noise Floor RF OUTPUT = 1900 MHz Output Power, POUT Modulator Voltage Gain Output P1dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Output IP2 Output IP3 Noise Floor RF OUTPUT = 2140 MHz Output Power, POUT Modulator Voltage Gain Output P1dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Test Conditions/Comments RF output range Min 700 Internal LO range External LO range 356.25 700 Baseband VIQ = 1 V p-p differential POUT − P(fLO ± (2 × fBB)) POUT − P(fLO ± (3 × fBB)) f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential I/Q input with 500 mV dc bias and no RF output, 20 MHz carrier offset I/Q input with 500 mV dc bias and −10 dBm RF output, 20 MHz carrier offset Baseband VIQ = 1 V p-p differential POUT − P(fLO ± (2 × fBB)) POUT − P(fLO ± (3 × fBB)) f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential I/Q input with 500 mV dc bias and no RF output, 20 MHz carrier offset I/Q input with 500 mV dc bias and −10 dBm RF output, 20 MHz carrier offset Baseband VIQ = 1 V p-p differential POUT − P(fLO ± (2 × fBB)) POUT − P(fLO ± (3 × fBB)) Rev. 0 | Page 3 of 44 Typ Max 3000 Unit MHz 2855 3000 MHz MHz 5.8 1.82 13.1 −44.0 −47.1 −0.15 −0.01 −66.1 −60.6 66.4 dBm dB dBm dBm dBc Degrees dB dBc dBc dBm 36.2 dBm −157.6 −157.3 dBm/Hz dBm/Hz 5.6 1.62 13.1 −39.2 −41.2 1.15 −0.0175 −66.2 −57.2 62.2 dBm dB dBm dBm dBc Degrees dB dBc dBc dBm 35.7 dBm −158.8 −158.1 dBm/Hz dBm/Hz 5 1.12 12.2 −40.3 −37.6 −1.15 −0.022 −57.9 −58.1 dBm dB dBm dBm dBc Degrees dB dBc dBc ADRF6720 Parameter Output IP2 Output IP3 Noise Floor RF OUTPUT = 2300 MHz Output Power, POUT Modulator Voltage Gain Output P1dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Output IP2 Output IP3 Noise Floor RF OUTPUT = 2600 MHz Output Power, POUT Modulator Voltage Gain Output P1dB Carrier Feedthrough Sideband Suppression Quadrature Error I/Q Amplitude Balance Second Harmonic Third Harmonic Output IP2 Output IP3 Noise Floor SYNTHESIZER SPECIFICATIONS Figure of Merit (FOM)1 REFERENCE CHARACTERISTICS REFIN Input Frequency REFIN Input Amplitude Phase Detector Frequency Data Sheet Test Conditions/Comments f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential I/Q input with 500 mV dc bias and no RF output, 20 MHz carrier offset I/Q input with 500 mV dc bias and −10 dBm RF output, 20 MHz carrier offset Min Baseband VIQ = 1 V p-p differential POUT − P(fLO ± (2 × fBB)) POUT − P(fLO ± (3 × fBB)) f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential I/Q input with 500 mV dc bias and no RF output, 20 MHz carrier offset I/Q input with 500 mV dc bias and −10 dBm RF output, 20 MHz carrier offset Baseband VIQ = 1 V p-p differential POUT − P(fLO ± (2 × fBB)) POUT − P(fLO ± (3 × fBB)) f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential f1BB = 3.5 MHz, f2BB = 4.5 MHz, baseband I/Q amplitude per tone = 0.45 V p-p differential I/Q input with 500 mV dc bias and no RF output, 20 MHz carrier offset I/Q input with 500 mV dc bias and −10 dBm RF output, 20 MHz carrier offset Synthesizer specifications referenced to the modulator output Typ 57.7 Max Unit dBm 32.6 dBm −157.9 −156.3 dBm/Hz dBm/Hz 4.6 0.62 dBm dB 11.8 −37.6 −36.6 −1.5 −0.0285 −54.8 −56.6 57.6 dBm dBm dBc Degrees dB dBc dBc dBm 30.4 dBm −159.2 −157.5 dBm/Hz dBm/Hz 3.9 −0.08 dBm dB 11.3 −36.5 −42.3 −0.55 −0.021 −60.3 −54.7 56.6 dBm dBm dBc Degrees dB dBc dBc dBm 29.9 dBm −159.2 −157.3 dBm/Hz dBm/Hz −218.5 dBc/Hz/Hz REFIN, MUXOUT pins 5.7 320 4 11.4 Rev. 0 | Page 4 of 44 MHz dBm 40 MHz Data Sheet Parameter MUXOUT Output Level MUXOUT Duty Cycle CHARGE PUMP Charge Pump Current Output Compliance Range PHASE NOISE, FREQUENCY = 940 MHz, fPFD = 38.4 MHz Integrated Phase Noise Reference Spurs PHASE NOISE, FREQUENCY = 1900 MHz, fPFD = 38.4 MHz Integrated Phase Noise Reference Spurs PHASE NOISE, FREQUENCY = 2140 MHz, fPFD = 38.4 MHz Integrated Phase Noise Reference Spurs ADRF6720 Test Conditions/Comments Low (lock detect output selected) High (lock detect output selected) Min Programmable to 250 μA, 500 μA, 750 μA, or 1000 μA Typ 0.25 2.7 50 Max 1000 1 2.8 Unit V V % μA V Closed-loop operation (20 kHz loop filter, see Figure 44 for loop filter design) 10 kHz offset 100 kHz offset 1 MHz offset 5 MHz offset 10 MHz offset 20 MHz offset 1 kHz to 40 MHz integration bandwidth, with spurs −97.8 −120.8 −144.4 −154.4 −154.9 −155.3 0.175 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz ° rms fPFD fPFD × 2 fPFD × 3 fPFD × 4 Closed-loop operation (20 kHz loop filter, see Figure 44 for loop filter design) −104.8 −97.8 −98.8 −103 dBc dBc dBc dBc 10 kHz offset 100 kHz offset 1 MHz offset 5 MHz offset 10 MHz offset 20 MHz offset 1 kHz to 40 MHz integration bandwidth, with spurs −91.5 −114.5 −139.9 −151.4 −153 −153.5 0.332 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz ° rms fPFD fPFD × 2 fPFD × 3 fPFD × 4 Closed-loop operation (20 kHz loop filter, see Figure 44 for loop filter design) −102 −90.8 −93.6 −100.5 dBc dBc dBc dBc 10 kHz offset 100 kHz offset 1 MHz offset 5 MHz offset 10 MHz offset 20 MHz offset 1 kHz to 40 MHz integration bandwidth, with spurs −92 −115.7 −140.3 −151.3 −152.1 −152.9 0.305 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz ° rms fPFD fPFD × 2 fPFD × 3 fPFD × 4 −95.9 −93.1 −87.4 −91.5 dBc dBc dBc dBc Rev. 0 | Page 5 of 44 ADRF6720 Parameter PHASE NOISE, FREQUENCY = 2300 MHz, fPFD = 38.4 MHz Integrated Phase Noise Reference Spurs PHASE NOISE, FREQUENCY = 2600 MHz, fPFD = 38.4 MHz Integrated Phase Noise Reference Spurs LO INPUT/OUTPUT LO Output Frequency Range LO Output Level LO Input Level LO Input Impedance BASEBAND INPUTS I and Q Input DC Bias Level Bandwidth Differential Input Impedance Differential Input Capacitance OUT ENABLE Turn-On Settling Time Turn-Off Settling Time Data Sheet Test Conditions/Comments Closed-loop operation (20 kHz loop filter, see Figure 44 for loop filter design) Min Typ Max Unit 10 kHz offset 100 kHz offset 1 MHz offset 5 MHz offset 10 MHz offset 20 MHz offset 1 kHz to 40 MHz integration bandwidth, with spurs −94.1 −114.6 −138.7 −150.1 −151.4 −152.6 0.270 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz ° rms fPFD fPFD × 2 fPFD × 3 fPFD × 4 Closed-loop operation (20 kHz loop filter, see Figure 44 for loop filter design) −100.8 −95.6 −89.4 −93.1 dBc dBc dBc dBc 10 kHz offset 100 kHz offset 1 MHz offset 5 MHz offset 10 MHz offset 20 MHz offset 1 kHz to 40 MHz integration bandwidth, with spurs −91.5 −111.3 −136.8 −148.3 −150 −150.7 0.378 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz °rms fPFD fPFD × 2 fPFD × 3 fPFD × 4 −97.4 −89.3 −95.2 −91.4 dBc dBc dBc dBc LO output 700 2 × LO or 1 × LO mode, into a 50 Ω load, LO buffer enabled at 2140 MHz LO_DRV_LVL = 0 LO_DRV_LVL = 1 LO_DRV_LVL = 2 Externally applied LO, PLL disabled Externally applied LO, PLL disabled I± and Q± pins −6 2855 −5.1 −0.5 3 0 50 +6 MHz dBm dBm dBm dBm Ω 0.5 V 1 dB Frequency = 10 MHz2 >1000 465 MHz Ω Frequency = 10 MHz2 1.84 pF 190 ns 20 ns ENBL pin ENBL high to low (90% of envelope), when Register 0x01[10] = 1, Register 0x10[10] = 1 ENBL low to high (10% of envelope), when Register 0x01[10] = 1, Register 0x10[10] = 1 Rev. 0 | Page 6 of 44 Data Sheet ADRF6720 Parameter DIGITAL LOGIC Input Voltage High (VIH) Input Voltage Low (VIL) Input Current (IIH/IIL) Input Capacitance (CIN) Output Voltage High (VOH) Output Voltage Low (VOL) POWER SUPPLIES Voltage Range Supply Current Test Conditions/Comments SCLK, SDIO, CS, and ENBL Min Typ Max Unit 0.7 1 V V µA pF 1.4 −1 5 IOH = −100 uA 2.3 V IOL = 100 uA 0.2 VPOSx Tx mode at internal LO mode (PLL, internal VCO , and modulator enabled, LO output driver disabled) Tx mode at external 1× LO mode (PLL, internal VCO disabled, modulator enabled, LO output driver disabled) LO output driver; LO_DRV_LVL bits (Register 0x22[7:6]) = 10 Power-down mode V 3.3 425 V mA 228 mA 50 14.5 mA mA The figure of merit (FOM) is computed as phase noise (dBc/Hz) – 10log10(fPFD) − 20log10(fLO/fPFD). The FOM was measured across the full LO range, with fREF = 153.6 MHz, fREF power = 4 dBm with a 38.4 MHz fPFD. The FOM was computed at a 50 kHz offset. 2 Refer to Figure 47 for a plot of input impedance over frequency. 1 TIMING CHARACTERISTICS Table 2. Parameter tSCLK tDS tDH tS tH tHIGH tLOW tACCESS tz Description Serial clock period Setup time between data and rising edge of SCLK Hold time between data and rising edge of SCLK Setup time between falling edge of CS and SCLK Hold time between rising edge of CS and SCLK Minimum period that SCLK should be in a logic high state Minimum period that SCLK should be in a logic low state Maximum time delay between falling edge of SCLK and output data valid for a read operation Maximum time delay between CS deactivation and SDIO bus return to high impedance tHIGH tDS tS Min 38 8 8 10 10 10 10 Max 231 5 Units ns ns ns ns ns ns ns ns ns tH tSCLK tACCESS tLOW tDH Typ CS DON'T CARE SDIO DON'T CARE DON'T CARE tZ A6 A5 A4 A3 A2 A1 A0 R/W D15 D14 D13 Figure 2. Serial Port Timing Diagram Rev. 0 | Page 7 of 44 D3 D2 D1 D0 DON'T CARE 12134-002 SCLK ADRF6720 Data Sheet ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 3. Parameter Supply Voltage I+, I−, Q+, Q− LOIN+, LOIN− REFIN ENBL VTUNE CS, SCLK, SDIO Maximum Junction Temperature Operating Temperature Range Storage Temperature Range θJA is thermal resistance, junction to ambient (°C/W), and θJC is thermal resistance, junction to case (°C/W). Rating −0.3 V to +3.6 V −0.5 V to +1.5 V 16 dBm differential −0.3 V to +3.6 V −0.3 V to +3.6 V −0.3 V to +3.6 V −0.3 V to +3.6 V 150°C −40°C to +85°C −65°C to +150°C Table 4. Thermal Resistance Package Type 40-Lead LFCSP 1 θJA1 30.23 θJC1 0.44 Unit °C/W See JEDEC standard JESD51-2 for information on optimizing thermal impedance. ESD CAUTION Stresses at or above those listed under Absolute Maximum Ratings may cause permanent damage to the product. This is a stress rating only; functional operation of the product at these or any other conditions above those indicated in the operational section of this specification is not implied. Operation beyond the maximum operating conditions for extended periods may affect product reliability. Rev. 0 | Page 8 of 44 Data Sheet ADRF6720 40 39 38 37 36 35 34 33 32 31 VPOS8 REFIN GND GND CP VPOS7 LOIN+ LOIN– VTUNE DECL3 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS ADRF6720 TOP VIEW (Not to Scale) 30 29 28 27 26 25 24 23 22 21 VPOS6 GND DECL2 ENBL VPOS5 GND RFOUT GND VPOS4 NIC NOTES 1. NIC = NOT INTERNALLY CONNECTED. 2. SOLDER THE EXPOSED PAD TO A LOW IMPEDANCE GROUND PLANE. 12134-003 VPOS2 DECL1 SDIO SCLK CS GND VPOS3 LOOUT+ LOOUT– GND 11 12 13 14 15 16 17 18 19 20 MUXOUT 1 GND 2 I+ 3 I– 4 GND 5 VPOS1 6 GND 7 Q– 8 Q+ 9 GND 10 Figure 3. Pin Configuration Table 5. Pin Function Descriptions Pin No. 1 Mnemonic MUXOUT 2, 10 3, 4 5, 7 6 GND I+, I− GND VPOS1 8, 9 11 Q−, Q+ VPOS2 12 DECL1 13 14 15 16 17 SDIO SCLK CS GND VPOS3 18, 19 LOOUT+, LOOUT− 20 21 22 GND NIC VPOS4 23, 25 24 26 GND RFOUT VPOS5 27 ENBL 28 DECL2 29 GND Description Multiplexer Output. This output allows a digital lock detect signal, a voltage proportional to absolute temperature (VPTAT), or a buffered, frequency-scaled reference signal to be accessed externally. The output is selected by programming Bits[6:4] in Register 0x21. Baseband Ground. Differential In-Phase Baseband Inputs. Mixer Core (I and Q) Ground. 3.3 V Supply Voltage for Baseband. Decouple VPOS1 with 100 pF and 0.1 µF capacitors located close to the pin. Differential Quadrature Baseband Inputs. 3.3 V Supply Voltage for 2.5 V LDO. Decouple VPOS2 with 100 pF and 0.1 µF capacitors located close to the pin. Decoupling Pin for 2.5 V LDO. Connect 100 pF, 0.1 µF, and 10 µF capacitors between this pin and ground. Serial Data Input/Output for SPI. Serial Clock Input/Output for SPI. Chip Select Input/Output for SPI. Digital Ground. 3.3 V Supply Voltage for LO. Decouple VPOS3 with 100 pF and 0.1 µF capacitors located close to the pin. Differential LO Outputs. Either the internally generated LO or external 1 × LO/2 × LO is available at 1 × LO or 2 × LO on these pins. LO Ground. Not Internally Connected. This pin can be left open or tied to RF ground. 3.3 V Supply Voltage for RF. Decouple VPOS4 with 100 pF and 0.1 µF capacitors located close to the pin. RF Ground. Single-Ended 0 V DC RF Output. 3.3 V Supply Voltage for RF. Decouple VPOS5 with 100 pF and 0.1 µF capacitors located close to the pin. Enables/Disables the Circuit Blocks. References the settings at Register 0x01 and Register 0x10. Refer to the ENBL section for more information. Decoupling Pin for VCO LDO. Connect 100 pF, 0.1 µF, and 10 µF capacitors between this pin and ground. VCO Ground. Rev. 0 | Page 9 of 44 ADRF6720 Data Sheet Pin No. 30 Mnemonic VPOS6 31 DECL3 32 33, 34 35 VTUNE LOIN−, LOIN+ VPOS7 36 37 38 39 40 CP GND GND REFIN VPOS8 EP Description 3.3 V Supply Voltage for VCO LDO. Decouple VPOS6 with 100 pF and 0.1 µF capacitors located close to the pin. Decoupling Pin for VCO LDO. Connect 100 pF, 0.1 µF, and 10 µF capacitors between this pin and ground. VCO Tuning Voltage. Differential External LO Inputs. 3.3 V Supply Voltage for Charge Pump. Decouple VPOS7 with 100 pF and 0.1 µF capacitors located close to the pin. Charge Pump Output. Charge Pump Ground. PLL Reference Ground. PLL Reference Input. 3.3 V Supply Voltage for PLL Reference. Decouple VPOS8 with 100 pF and 0.1 µF capacitors located close to the pin. Exposed Pad. Solder the exposed pad to a low impedance ground plane. Rev. 0 | Page 10 of 44 Data Sheet ADRF6720 TYPICAL PERFORMANCE CHARACTERISTICS VPOSx = 3.3 V; TA = 25°C; baseband I/Q amplitude = 1 V p-p differential sine waves in quadrature with a 500 mV dc bias; baseband I/Q frequency (fBB) = 1 MHz; fPFD = 38.4 MHz; fREF = 153.6 MHz at 4 dBm referred to 50 Ω (1 V p-p); 20 kHz loop filter, unless otherwise noted. 9 9 SSB OUTPUT POWER (dBm) 8 7 6 5 4 3 5 4 3 1 1200 1700 2200 2700 0 700 16 1dB OUTPUT COMPRESSION (dBm) 10 8 6 4 2700 14 3.15V 3.3V 3.45V 12 10 8 6 4 1700 2200 2700 LO FREQUENCY (MHz) 0 700 12134-005 1200 2200 2700 Figure 8. SSB 1 dB Output Compression Point (OP1dB) vs. LO Frequency (fLO) and Supply 0 TA = –40°C TA = +25°C TA = +85°C –10 CARRIER FEEDTHROUGH (dBm) –10 1700 LO FREQUENCY (MHz) Figure 5. SSB 1 dB Output Compression Point (OP1dB) vs. LO Frequency (fLO) and Temperature; Multiple Devices Shown 0 1200 12134-008 2 2 –20 –30 –40 –50 –60 –70 TA = –40°C TA = +25°C TA = +85°C –20 –30 –40 –50 –60 –70 1700 2200 LO FREQUENCY (MHz) 2700 –90 700 12134-006 1200 1200 1700 2200 LO FREQUENCY (MHz) Figure 6. Carrier Feedthrough vs. LO Frequency (fLO) and Temperature Before Nulling; Multiple Devices Shown 2700 12134-009 –80 –80 –90 700 2200 16 12 0 700 1700 Figure 7. SSB Output Power (POUT) vs. LO Frequency (fLO) and Supply TA = –40°C TA = +25°C TA = +85°C 14 1200 LO FREQUENCY (MHz) Figure 4. Single Sideband (SSB) Output Power (POUT) vs. LO Frequency (fLO) and Temperature; Multiple Devices Shown 1dB OUTPUT COMPRESSION (dBm) 6 1 LO FREQUENCY (MHz) CARRIER FEEDTHROUGH (dBm) 7 2 0 700 3.15V 3.3V 3.45V 8 2 12134-004 SSB OUTPUT POWER (dBm) 10 TA = –40°C TA = +25°C TA = +85°C 12134-007 10 Figure 9. Carrier Feedthrough vs. LO Frequency (fLO) and Temperature After Nulling Using DCOFF_I and DCOFF_Q at 25°C; Multiple Devices Shown Rev. 0 | Page 11 of 44 ADRF6720 Data Sheet 0 0 TA = –40°C TA = +25°C TA = +85°C –20 –30 –40 –50 –60 –70 –30 –40 –50 –60 –70 LO FREQUENCY (MHz) –90 700 OIP2 –20 TA = –40°C TA = +25°C TA = +85°C 60 50 40 30 OIP3 20 10 1200 1700 2200 2700 LO FEQUENCY (MHz) 10 –30 5 SIDEBAND SUPPRESSION (dBc) –40 0 –5 –50 –60 –10 CARRIER FEEDTHROUGH (dBm) SECOND-ORDER HARMONIC (dBc) –70 –80 0.1 1 SECOND-ORDER HARMONIC (dBc), THIRD-ORDER HARMONIC (dBc), CARRIER FEEDTHROUGH (dBm), SIDEBAND SUPPRESSION (dBc) SSB OUTPUT POWER (dBm) 15 SSB OUTPUT POWER (dBm) –20 –50 –60 –70 –80 1200 1700 2200 2700 0 –15 –20 10 BASEBAND INPUT VOLTAGE (V p-p Differential) Figure 12. SSB Output Power, Second- and Third-Order Harmonics, Carrier Feedthrough, and Sideband Suppression vs. Baseband Differential Input Voltage (fOUT = 940 MHz) 20 THIRD-ORDER HARMONIC (dBC) –10 –20 –30 15 SSB OUTPUT POWER (dBm) 10 SIDEBAND SUPPRESSION (dBC) 5 –40 0 CARRIER FEEDTHROUGH (dBm) –50 –60 SECOND-ORDER HARMONIC (dBC) –80 0.1 –5 –10 –15 –70 12134-012 –10 –40 Figure 14. Second- and Third-Order Harmonics vs. LO Frequency (fLO) and Temperature (POUT ≈ 5 dBm) 20 THIRD-ORDER HARMONIC (dBc) –30 SECOND-ORDER THIRD-ORDER LO FREQUENCY (MHz) Figure 11. OIP3 and OIP2 vs. LO Frequency (fLO) and Temperature (POUT ≈ −5 dBm per Tone); Multiple Devices Shown 0 TA = –40°C TA = +25°C TA = +85°C –90 700 12134-011 0 700 2700 2200 Figure 13. Sideband Suppression vs. LO Frequency (fLO) and Temperature After Nulling Using I_LO and Q_LO at 25°C; Multiple Devices Shown THIRD-ORDER HARMONIC (dBc), SECOND-ORDER HARMONIC (dBc) 70 1700 LO FREQUENCY (MHz) Figure 10. Sideband Suppression vs. LO Frequency (fLO) and Temperature Before Nulling; Multiple Devices Shown 80 1200 SSB OUTPUT POWER (dBm) 2700 1 –20 10 BASEBAND INPUT VOLTAGE (V p-p Differential) Figure 15. SSB Output Power, Second- and Third-Order Harmonics, Carrier Feedthrough, and Sideband Suppression vs. Baseband Differential Input Voltage (fOUT = 2140 MHz) Rev. 0 | Page 12 of 44 12134-015 2200 12134-013 1700 12134-014 1200 12134-010 –90 700 OUTPUT IP3 AND IP2 (dBm) –20 –80 –80 SECOND-ORDER HARMONIC (dBc), THIRD-ORDER HARMONIC (dBc), CARRIER FEEDTHROUGH (dBm), SIDEBAND SUPPRESSION (dBc) TA = –40°C TA = +25°C TA = +85°C –10 SIDEBAND SUPPRESSION (dBc) SIDEBAND SUPPRESSION (dBc) –10 Data Sheet ADRF6720 0 15 –20 –20 5 –40 0 –50 –5 SECOND-ORDER HARMONIC (dBC) –60 SIDEBAND SUPPRESSION (dBC) –70 –80 0.1 1 –10 –120 –20 10 –180 10M TA = –40°C TA = +25°C TA = +85°C –40 –60 –80 –100 –120 –140 –140 –160 –160 10k 100k 1M 10M OFFSET FREQUENCY (Hz) –180 1k 1M 10M Figure 20. Closed-Loop Phase Noise vs. Offset Frequency and Temperature, fLO = 2140 MHz; 20 kHz Loop Filter 0 TA = –40°C TA = +25°C TA = +85°C –20 100k OFFSET FREQUENCY (Hz) Figure 17. Closed-Loop Phase Noise vs. Offset Frequency and Temperature, fLO = 1900 MHz; 20 kHz Loop Filter 0 10k 12134-020 PHASE NOISE (dBc/Hz) –120 TA = –40°C TA = +25°C TA = +85°C –20 –40 PHASE NOISE (dBc/Hz) –40 –60 –80 –100 –120 –60 –80 –100 –120 –140 –140 –160 –160 10k 100k 1M OFFSET FREQUENCY (Hz) 10M –180 12134-018 1k 1M –20 –100 –180 100k 0 –80 1k 10k Figure 19. Closed-Loop Phase Noise vs. Offset Frequency and Temperature, fLO = 940 MHz; 20 kHz Loop Filter TA = –40°C TA = +25°C TA = +85°C –60 –180 1k OFFSET FREQUENCY (Hz) 12134-017 PHASE NOISE (dBc/Hz) –100 –140 –40 PHASE NOISE (dBc/Hz) –80 –160 Figure 16. SSB Output Power, Second- and Third-Order Harmonics, Carrier Feedthrough, and Sideband Suppression vs. Baseband Differential Input Voltage (fOUT = 2600 MHz) –20 –60 –15 BASEBAND INPUT VOLTAGE (V p-p Differential) 0 –40 Figure 18. Closed-Loop Phase Noise vs. Offset Frequency and Temperature, fLO = 2300 MHz; 20 kHz Loop Filter 1k 10k 100k 1M OFFSET FREQUENCY (Hz) 10M 12134-021 –30 10 CARRIER FEEDTHROUGH (dBm) TA = –40°C TA = +25°C TA = +85°C 12134-019 SSB OUTPUT POWER (dBm) PHASE NOISE (dBc/Hz) –10 20 SSB OUTPUT POWER (dBm) THIRD-ORDER HARMONIC (dBC) 12134-016 SECOND-ORDER HARMONIC (dBc), THIRD-ORDER HARMONIC (dBc), CARRIER FEEDTHROUGH (dBm), SIDEBAND SUPPRESSION (dBc) 0 Figure 21. Closed-Loop Phase Noise vs. Offset Frequency and Temperature, fLO = 2600 MHz; 20 kHz Loop Filter Rev. 0 | Page 13 of 44 ADRF6720 OFFSET = 1kHz –90 –130 –140 OFFSET = 5MHz –120 –130 OFFSET = 1MHz –140 –150 –150 –160 –160 1200 1700 2200 2700 LO FREQUENCY (MHz) Figure 22. Closed-Loop Phase Noise vs. LO Frequency at 1 kHz, 100 kHz, and 5 MHz Offsets 1 × PFD FREQUENCY 3 × PFD FREQUENCY –170 700 –85 SPUR LEVEL (dBc) –85 –90 –95 –100 –105 –95 –100 –105 –110 –115 –115 –120 700 –120 700 2700 –75 2 × PFD FREQUENCY 4 × PFD FREQUENCY –85 SPUR LEVEL (dBc) –80 –90 –95 –100 –105 –95 –100 –105 –115 –115 –120 700 –120 700 12134-024 –110 2700 2700 –90 –110 2200 2200 –75 –85 1700 1700 –70 TA = –40°C TA = +25°C TA = +85°C LO FREQUENCY (MHz) 1200 1 × PFD FREQUENCY 3 × PFD FREQUENCY Figure 26. PLL Reference Spurs vs. LO Frequency (1 × PFD and 3 × PFD) at LO Output –80 1200 TA = –40°C TA = +25°C TA = +85°C LO FREQUENCY (MHz) Figure 23. PLL Reference Spurs vs. LO Frequency (1 × PFD and 3 × PFD) at Modulator Output –70 2700 –90 –110 2200 2200 –75 –80 1700 1700 –70 TA = –40°C TA = +25°C TA = +85°C LO FREQUENCY (MHz) 1200 Figure 25. Closed-Loop Phase Noise vs. LO Frequency at 10 kHz, 1 MHz, and 10 MHz Offsets –80 1200 OFFSET = 10MHz LO FREQUENCY (MHz) 12134-023 SPUR LEVEL (dBc) –75 SPUR LEVEL (dBc) –110 12134-025 PHASE NOISE (dBc/Hz) –120 12134-022 PHASE NOISE (dBc/Hz) OFFSET = 100kHz –110 –70 OFFSET = 10kHz –100 –100 –170 700 TA = –40°C TA = +25°C TA = +85°C 12134-026 –90 –80 TA = –40°C TA = +25°C TA = +85°C Figure 24. PLL Reference Spurs vs. LO Frequency (2 × PFD and 4 × PFD) at Modulator Output TA = –40°C TA = +25°C TA = +85°C 1200 2 × PFD FREQUENCY 4 × PFD FREQUENCY 1700 2200 LO FREQUENCY (MHz) 2700 12134-027 –80 Data Sheet Figure 27. PLL Reference Spurs vs. LO Frequency (2 × PFD and 4 × PFD) at LO Output Rev. 0 | Page 14 of 44 Data Sheet ADRF6720 0.8 2.4 0.7 2.2 VTUNE (V) 0.6 0.5 0.4 2 1.8 1.6 0.3 1.4 0.2 1.2 0.1 1.0 0 700 1200 TA = –40°C TA = +25°C TA = +85°C 2.6 1700 2200 2700 LO FREQUENCY (MHz) 0.8 2800 12134-028 PHASE NOISE (dBc/Hz) 5800 2300.78MHz 2156.06MHz 2009.22MHz –80 –100 –120 –140 10k 100k 1M 10M 100M FREQUENCY (Hz) –160 12134-029 1k Figure 29. Open-Loop VCO Phase Noise for VCO 0 Measured at 2300.22 MHz, 2579.83 MHz, and 2860.8 MHz (VCO ÷ 2) 1k 10k 100k 1M 100M Figure 32. Open-Loop VCO Phase Noise for VCO 1 Measured at 2009.22 MHz, 2156.06 MHz, and 2300.78 MHz (VCO ÷ 2) –40 –40 10M FREQUENCY (Hz) 12134-032 PHASE NOISE (dBc/Hz) –120 –140 1751.47MHz 1587.28MHz 1425.29MHz 2010.75MHz 1882.97MHz 1750.48MHz –60 PHASE NOISE (dBc/Hz) –60 PHASE NOISE (dBc/Hz) 5300 –60 –100 –80 –100 –120 –80 –100 –120 –140 –140 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M –160 12134-030 –160 4800 –40 –80 –160 4300 Figure 31. VTUNE vs. VCO Frequency and Temperature 2860.8MHz 2579.83MHz 2300.22MHz –60 3800 VCO FREQUENCY (MHz) Figure 28. Integrated Phase Noise with Spurs vs. LO Frequency and Temperature –40 3300 Figure 30. Open-Loop VCO Phase Noise for VCO 2 Measured at 1750.48 MHz, 1882.97 MHz, and 2010.75 MHz (VCO ÷ 2) 1k 10k 100k 1M FREQUENCY (Hz) 10M 100M 12134-033 INTEGRATED PHASE NOISE (°rms) 0.9 2.8 TA = –40°C TA = +25°C TA = +85°C 12134-031 1.0 Figure 33. Open-Loop VCO Phase Noise for VCO 3 Measured at 1425.29 MHz, 1587.28 MHz, and 1751.47 MHz (VCO ÷ 2) Rev. 0 | Page 15 of 44 ADRF6720 Data Sheet 100 80 TA = –40°C TA = +25°C TA = +85°C 4 3 LO OUTPUT POWER (dBm) 90 CUMULATIVE PERCENTAGE (%) 5 940MHz 1900MHz 2140MHz 2300MHz 2600MHz 70 60 50 40 30 20 2 1 LO_DRV_LVL = 2 LO_DRV_LVL = 1 0 –1 –2 –3 LO_DRV_LVL = 0 –4 –5 –6 10 12134-034 NOISE FLOOR (dBm/Hz) –8 700 Figure 34. Noise Floor Cumulative Distribution at Various LO Frequencies Using Internal LO; I/Q Input with 500 mV DC Bias and No RF Output 520 500 2700 TA = –40°C TA = +25°C TA = +85°C 60 50 40 30 460 440 420 400 380 20 360 10 340 0 –163 –162 –161 –160 –159 –158 –157 –156 –155 –154 –153 NOISE FLOOR (dBm/Hz) 320 700 Figure 35. Noise Floor Cumulative Distribution at Various LO Frequencies Using Internal LO; I/Q Input with 500 mV DC Bias and RF Output = −10 dBm 1200 1700 2200 2700 LO FREQUENCY (MHz) 12134-039 SUPPLY CURRENT (mA) 480 70 12134-035 CUMULATIVE PERCENTAGE (%) 2200 Figure 37. LO Output Power vs. LO Frequency at Various LO_DRV_LVL Settings 940MHz 1900MHz 2140MHz 2300MHz 2600MHz 80 1700 LO FREQUENCY (MHz) 100 90 1200 12134-037 –7 0 –163 –162 –161 –160 –159 –158 –157 –156 –155 –154 –153 Figure 38. Supply Current vs. LO Frequency and Temperature (PLL and I/Q Modulator Enabled, LO Buffer Disabled) 20 0 –5 10 5 0 –5 –10 –15 –20 –10 –25 –15 0 0.5 1.0 1.5 2.0 2.5 3.0 TIME (ms) 3.5 4.0 4.5 5.0 –30 0.7 12134-036 –20 Figure 36. Frequency Deviation from LO Frequency at LO = 1.91 GHz to 1.9 GHz vs. Lock Time BAL_CIN = 0, BAL_COUT = 0 BAL_CIN = 1, BAL_COUT = 0 BAL_CIN = 2, BAL_COUT = 0 BAL_CIN = 3, BAL_COUT = 0 BAL_CIN = 4, BAL_COUT = 0 BAL_CIN = 8, BAL_COUT = 0 BAL_CIN = 9, BAL_COUT = 0 BAL_CIN = 10, BAL_COUT = 0 BAL_CIN = 11, BAL_COUT = 0 BAL_CIN = 12, BAL_COUT = 0 BAL_CIN = 13, BAL_COUT = 0 BAL_CIN = 14, BAL_COUT = 0 BAL_CIN = 15, BAL_COUT = 0 BAL_CIN = 15, BAL_COUT = 3 1.2 1.7 2.2 LO FREQUENCY (GHz) 2.7 12134-040 RETURN LOSS (dB) FREQUENCY DEVIATION (MHz) 15 Figure 39. RF Output Return Loss vs. LO Frequency (fLO) for Multiple BAL_CIN and BAL_COUT Combinations Rev. 0 | Page 16 of 44 Data Sheet ADRF6720 0 0 –2 –5 RETURN LOSS (dB) –6 –8 –10 –12 –14 –10 –15 –20 –25 –16 –30 –20 0.3 1.3 2.3 3.3 4.3 5.3 LO FREQUENCY (GHz) 6.3 Figure 40. LO Input Return Loss vs. LO Frequency (fLO) –35 0.3 1.3 2.3 3.3 4.3 5.3 LO FREQUENCY (GHz) Figure 41. LO Output Return Loss vs. LO Frequency (fLO) Rev. 0 | Page 17 of 44 6.3 12134-042 –18 12134-041 RETURN LOSS (dB) –4 ADRF6720 Data Sheet THEORY OF OPERATION Internal LO Mode The ADRF6720 integrates a high performance broadband I/Q modulator with a fractional-N PLL and low noise multicore VCOs. The baseband inputs mix with the LO generated internally or provided externally, and convert it to a singleended RF using an integrated RF balun. A block diagram of the device is shown in Figure 1. The ADRF6720 is programmed via an SPI. For internal LO mode, the ADRF6720 uses the on-chip PLL and VCO to synthesize the frequency of the LO signal. The PLL, shown in Figure 42, consists of a reference path, phase and frequency detector (PFD), charge pump, and a programmable integer divider with prescaler. The reference path takes in a reference clock and divides it down by a factor of 2, 4, or 8, or multiplies it by a factor of 1 or 2, and then passes it to the PFD. The PFD compares this signal to the divided down signal from the VCO. Depending on the PFD polarity selected, the PFD sends either an up or down signal to the charge pump if the VCO signal is either slow or fast compared to the reference frequency. The charge pump sends a current pulse to the offchip loop filter to increase or decrease the tuning voltage (VTUNE). LO GENERATION BLOCK The ADRF6720 supports the use of both internal and external LO signals for the mixers. The internal LO is generated by an on-chip VCO, which is tunable over an octave frequency range of 2850 MHz to 5710 MHz. The output of the VCO is phaselocked to an external reference clock through a fractional-N PLL that is programmable through the SPI control registers. To produce in-phase and quadrature phase LO signals over the 356.25 MHz to 2855 MHz frequency range to drive the mixers, steer the VCO outputs through a combination of frequency dividers, as shown in Figure 42. The ADRF6720 integrates four VCO cores, covering an octave range of 2850 MHz to 5710 MHz. Table 6 lists the frequency range covered by each VCO. The desired VCO can be selected by addressing the VCO_SEL bits at Register 0x22[2:0]. Alternatively, an external signal can be used with the dividers or a polyphase phase splitter to generate the LO signals in quadrature to the mixers. In demanding applications that require the lowest possible phase noise performance, it may be necessary to source the LO signal externally. The different methods of quadrature LO generation and the control register programming needed are listed in Table 6. The LO source and quadrature generation path can be selected by setting the QUAD_DIV_EN bit (Register 0x01[9]) and the LO_1XVCO_EN bit (Register 0x01[11]). The mode of the VCO signal through a polyphase filter is intended to extend the operating frequency with an internal VCO and is only useful for baseband input frequencies high enough to prevent the RF output from pulling the VCO. POLYPHASE FILTER LOIN+ 34 REF_SEL REG 0x21[2:0] ÷4 PFD ÷2 + ×1 QUAD_DIV_EN REG 0x01[9] ÷1, ÷2, ÷4 QUAD DIVIDER VTUNE CP CHARGE PUMP 32 36 I+ I– TO MIXER Q+ Q– LPF CP_CTL REG 0x20[14:0] ×2 LO_1XVCO_EN REG 0x01[11] EXTERNAL LOOP FILTER PFD_POLARITY REG 0x21[3] ÷8 REFIN 39 LOIN– 33 DIV8 _EN/ DIV4_EN REG 0x22[4:3] N = INT + FRAC MOD ÷1,÷2 ÷2 DRVDIV2_EN REG 0x22[5] LOOUT+ LOOUT– MUXOUT 1 VPTAT DIV_MODE: REG 0x02[11] INT_DIV: REG 0x02[10:0] FRAC_DIV: REG 0x03[15:0] MOD_DIV: REG 0x04[15:0] REF_MUX_SEL REG 0x21[6:4] Figure 42. LO Block Diagram Rev. 0 | Page 18 of 44 VCO_SEL REG 0x22[2:0] LO_DRV2X_EN REG 0x01[8] LO_DRV1X_EN REG 0x01[7] 12134-043 LOCK_DET Data Sheet ADRF6720 Table 6. LO Mode Selection LO Selection Internal (VCO) External 1 fVCO or fEXT (MHz) 2850 to 3500 3500 to 4020 4020 to 4600 4600 to 5710 2855 to 3000 700 to 6000 700 to 3000 Quadrature Generation Divide by 2 Divide by 2 Divide by 2 Divide by 2 Polyphase Divide by 2 Polyphase QUAD_DIV_EN (Register 0x01[9]) 1 1 1 1 0 1 0 LO_1XVCO_EN (Register 0x1 [11]) 0 0 0 0 0 0 0 Enables (Register 0x01[6:0]) 111 111X1 111 111X1 111 111X1 111 111X1 111 111X1 101 000X1 000 000X1 VCO_SEL (Register 0x22[2:0]) 011 010 001 000 011 1XX1 XXX1 X = don’t care. LO Frequency and Dividers The signal coming from the VCO or the external LO inputs goes through a series of dividers before it is buffered to drive the active mixers. Two programmable divide-by-2 stages divide the frequency of the incoming signal by 1, 2, or 4 before reaching the quadrature divider that further divides the signal frequency by 2 to generate the in-phase and quadrature phase LO signals for the mixers. The control bits (Register 0x22[4:3]) needed to select the different LO frequency ranges are listed in Table 7. Table 7. LO Frequency and Dividers LO Frequency Range (MHz) 1425 to 2855 712.5 to 1425 356.25 to 712.5 fVCO/fLO or fEXT LO/fLO 2 4 8 DIV8_EN (Register 0x22[4]) 0 0 1 DIV4_EN (Register 0x22[3]) 0 1 1 The N divider with divide-by-2 divides down the VCO signal to the PFD frequency. The N divider can be configured for fractional or integer mode by addressing the DIV_MODE bit (Register 0x02[11]). The default configuration is set for fractional mode. Use the following equations to determine the N value and PLL frequency: f VCO 2× N The loop filter is connected between the CP and VTUNE pins. The recommended components for 20 kHz filter designs are shown in Table 8 and referenced in Figure 44. The ADRF6720 closed-loop phase noise is characterized using a 20 kHz loop filter. Operation with an external VCO is possible. In this case, the output of the loop filter is connected to the tuning pin of the external VCO. The output of the VCO is brought back into the device on the LOIN+ and LOIN− pins. For assistance in designing loop filters with other characteristics, download the most recent revision of ADIsimPLL™ from http://www.analog.com/adisimpll. Component C57 R12 C58 R23 C59 R26 C60 20 kHz Loop Filter 2700 pF 300 Ω 100 nF 5.6 Ω 2700 pF 820 Ω 1500 pF PLL Lock Time FRAC N = INT + MOD f LO = Loop Filter Table 8. Recommended Loop Filter Components PLL Frequency Programming f PFD = locked. LO_DIVIDER is the final frequency divider ratio that divides the frequency of the VCO or the external LO signal down by 2, 4, or 8 before it reaches the mixer, as shown in Table 7. It takes time to lock the PLL after the last register is written. VCO band calibration time and loop settling time are used to determine the PLL lock time. f ×2× N fvco = PFD LO _ DIVIDER LO_DIVIDER where: fPFD is the phase frequency detector frequency. fVCO is the VCO frequency. N is the fractional divide ratio (INT + FRAC/MOD). INT is the integer divide ratio programmed in Register 0x02. FRAC is the fractional divider programmed in Register 0x03. MOD is the modulus divide ratio programmed in Register 0x04. fLO is the LO frequency going to the mixer core when the loop is After writing to the last register, the PLL automatically performs a VCO band calibration to choose the correct VCO band. This calibration takes approximately 94,208 PFD cycles. For a 40 MHz fPFD, this corresponds to 2.36 ms. After a band calibration completes, the feedback action of the PLL results in the VCO locking to the correct frequency. The speed to be locked depends on the nonlinear cycle slipping behavior, as well as the small signal settling of the loop. For an accurate estimation of the lock time, download the ADIsimPLL tool to Rev. 0 | Page 19 of 44 ADRF6720 Data Sheet capture these effects correctly. In general, higher bandwidth loops tend to lock more quickly than lower bandwidth loops. (fRF < fLO) when Q leads I and places the RF frequency above the LO (fRF > fLO) when I leads Q. The lock detect signal is available as one of the selectable outputs through the MUXOUT pin, with a logic high signifying that the loop is locked. The control bits for the MUXOUT pin are the REF_MUX_SEL bits (Register 0x21[6:4]), and the default configuration is for PLL lock detect. Table 10. LO Polarity Setting Address 0x32[11:10] Bit Name POL_Q 01 Required PLL/VCO Settings and Register Write Sequence In addition to writing to the necessary registers to configure the PLL and VCO for the desired LO frequency and phase noise performance, the registers listed in Table 9 are the required registers to write. To ensure that the PLL locks to the desired frequency, follow the proper write sequence of the PLL registers. Configure the PLL registers accordingly to achieve the desired frequency, and the last writes must be to Register 0x02 (INT_DIV), Register 0x03 (FRAC_DIV), or Register 0x04 (MOD_DIV). When Register 0x02, Register 0x03, and Register 0x04 are programmed, an internal VCO calibration initiates, which is the last step to locking the PLL. Table 9. Required PLL/VCO Register Writes Address 0x21[3] 0x49[13:0] Bit Name PFD_POLARITY SET_1[13:9], SET_0[8:0] Setting 0x01 0x14B4 Description Negative polarity Internal settings External LO Mode Use the VCO_SEL bits (Register 0x22[2:0]) to select external or internal LO mode. To configure for external LO mode, set Register 0x22[2:0] to 4 decimal and apply the differential LO signals to Pin 33 (LOIN−) and Pin 34 (LOIN+). The external LO frequency range is 700 MHz to 3 GHz. When the polyphase phase splitter is selected, a 1 × LO signal is required for the active mixer, or a 2 × LO can be used with the internal quadrature divider, as shown in Table 6. There is also the option of using an external VCO with the internal PLL. In this case, the PLL is enabled, but the VCO blocks are turned off. The LOIN+ and LOIN− input pins must be ac-coupled. When not in use, leave the LOIN+ and LOIN− pins unconnected. LO Polarity The ADRF6720 offers the flexibility of specifying the quadrature polarity on LO to the I channel or Q channel mixers. This specification determines whether the LO is injected above or below the RF frequency. RF frequency can place either above or below the LO depending on the Register 0x32[11:8] setting as well as the phase relationship between the baseband I and Q. For normal operation and characterization, the Register 0x32 settings are 2 decimal for POL_I (Register 0x32[9:8]) and 1 decimal for POL_Q (Register 0x32, Bits[11:10]). Setting Register 0x32 as such places the RF frequency below the LO Settings 10 0x32[9:8] POL_I 01 10 Description Quadrature polarity switch, Q channel Inverted Q channel polarity Normal polarity Quadrature polarity switch, I channel. Normal polarity Inverted I channel polarity LO Outputs The ADRF6720 can provide either a differential 1 × or 2 × LO output signal at the LOOUT+ and LOOUT− pins (Pin 18 and Pin 19, respectively). The availability of the LO signal makes it possible to daisy-chain many devices. One ADRF6720 device can serve as the master where the LO signal is sourced, and the subsequent slave devices can share the same LO output signal from the master. When the quadrature LO signals are generated using the quadrature divider, the output signal is available at either 2× or 1× the frequency of the LO signal at the mixer by setting LO_DRV2X_EN bit(Register 0x1[8]) and DRVDIV2_EN bit (Register 0x22[5]). However, 1× the frequency of the LO signal in this case has a phase ambiguity of 180° relative to the LO signal that drives the mixer core. Because of this phase ambiguity, the utility of this 1 × LO output signal as a system daisy-chained LO signal is compromised. To avoid this ambiguity, a second 1× the frequency of the LO signal output is made available after the quadrature divider. This second 1 × LO output path is enabled by setting the LO_DRV1X_EN bit (Register 0x01[7]) high. When the quadrature LO signals are generated using the polyphase phase splitter, the output signal is also available at 1× the frequency of the LO signal by setting LO_DRV1X_EN bit (Register 0x10[7]) high. Set the output to different drive levels by accessing the LO_DRV_LVL bits (Register 0x22[7:6]), as shown in Table 11. Table 11. LO Output Level at 2140 MHz LO_DRV_LVL (Register 0x22[7:6]) 00 01 10 Rev. 0 | Page 20 of 44 Amplitude (dBm) −5.1 −0.5 3 Data Sheet ADRF6720 BASEBAND Table 12. Optimum Balun Setting For Desired Frequency Range The input impedance of the baseband inputs is a 500 Ω differential. These inputs are designed to work with a 0.5 V common-mode voltage. To match the 100 Ω impedance of the DAC, place a shunt 125 Ω external resistor across the I and Q inputs. BAL_CIN 0 1 2 3 4 8 9 10 11 12 13 14 15 15 The voltages applied to the differential baseband inputs (I+, I−, Q+, and Q−) drive the V-to-I stage that converts baseband voltages into currents. The converted modulated signal current feeds the modulator mixer core. A programmable dc current can be added to both the I and Q channels to null any carrier feedthrough at the RF output. Refer to the Carrier Feedthrough Nulling section for more information The linearity can be optimized by adding the amplitude and phase correction signals to the current output via the MOD_RSEL (Register 0x31[12:6]) and MOD_CSEL (Register 0x31[5:0]) adjustment. Refer to the Linearity section for more information. ACTIVE MIXERS The ADRF6720 has two double balanced mixers: one for the in-phase channel (I channel) and the other for the quadrature channel (Q channel). They upconvert the modulated baseband signal currents by the LO signals to the RF. Tunable RFOUT Balun The ADRF6720 integrates a programmable balun operating over a frequency range from 700 MHz to 3000 MHz. It offers single-ended-to-differential conversion and provides additional common-mode noise rejection. The capacitors at the input and output of the balun in parallel with the inductive windings of the balun change the resonant frequency of the inductor capacitor (LC) tank. Therefore, selecting the proper combination of BAL_CIN (Register 0x30[3:0]) and BAL_COUT (Register 0x30[7:4]) sets the desired frequency and optimizes gain. Under most circumstances, it is suggested to set BAL_CIN and BAL_COUT over the frequency profile given in Table 12. However, for matching reasons, it is advantageous to tune the registers independently. BAL_CIN REG 0x30[3:0] Figure 43. Integrated Tunable Balun 12134-044 RFOUT BAL_COUT REG 0x30[7:4] BAL_COUT 0 0 0 0 0 0 0 0 0 0 0 0 0 3 Frequency Range (MHz) fRF > 1730 1550 < fRF < 1730 1380 < fRF < 1550 1250 < fRF < 1380 1170 < fRF < 1250 1100 < fRF < 1170 1020 < fRF < 1100 970 < fRF < 1020 930 < fRF < 970 890 < fRF < 930 840 < fRF < 890 820 < fRF < 840 740 < fRF < 820 680 < fRF < 740 ENBL The ENBL pin quickly enables/disables the RF output. The circuit blocks that are enabled/disabled with the ENBL pin can be programmed by setting the appropriate bits in the enables register (Register 0x01) and the ENBL_MASK register (Register 0x10). When the bits in the enables and the ENBL_MASK register are 1, pulling the ENBL pin low disables and pulling high enables the internal blocks more quickly than possible with an SPI write operation. Table 13. Enable/Disable Settings Register 0x01 Enables Bit1 0 Register 0x10 ENBL_MASK Bit1 X2 ENBL Pin Voltage X2 1 0 X2 1 1 >1.8 V 1 1