100 MHz to 1000 MHz
Integrated Broadband Receiver
ADRF6850
Rev. 0
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
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Tel: 781.329.4700 www.analog.com
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FEATURES
IQ quadrature demodulator
Integrated fractional-N PLL and VCO
Gain control range: 60 dB
Input frequency range: 100 MHz to 1000 MHz
Input P1dB: +12 dBm at 0 dB gain
Input IP3: +22.5 dBm at 0 dB gain
Noise figure: 11 dB at >39 dB gain, 49 dB at 0 dB gain
Baseband 1 dB bandwidth: 250 MHz in wideband mode,
50 MHz in narrow-band mode
SPI/I2C serial interface
Power supply: +3.3 V/350 mA
APPLICATIONS
Broadband communications
Cellular communications
Satellite communications
GENERAL DESCRIPTION
The ADRF6850 is a highly integrated broadband quadrature
demodulator, frequency synthesizer, and variable gain amplifier
(VGA). The device covers an operating frequency range from
100 MHz to 1000 MHz for use in both narrow-band and wideband
communications applications, performing quadrature demodu-
lation from IF directly to baseband frequencies.
The ADRF6850 demodulator includes a high modulus
fractional-N frequency synthesizer with integrated VCO,
providing better than 1 Hz frequency resolution, and a 60 dB
gain control range provided by a front-end VGA.
Control of all the on-chip registers is through a user-selected
SPI interface or I2C interface. The device operates from a single
power supply ranging from 3.15 V to 3.45 V.
FUNCTIONAL BLOCK DIAGRAM
QBB
QBB
R
SET
SDI/SDA
CLK/SCL
SDO
CS
GND MUXOUT
×2
DOUBLER 5-BIT
DIVIDER
REFERENCE
CHARGE
PUMP
CURRENT S E TTING
REFIN ÷2 PHASE
FREQUENCY
DETECTOR
SEQUENCED
GAIN
INTERFACE
+
–
DRIVER VCO
CORE
0°/90°
VCC1 VCC2 VCC3 VCC4 VCC5 VCC6 VCC7 VCC8 VCC9 LOMON LOMON
ADRF6850
RFI
RFI
RFCM
VGAIN
60dB
GAIN CONTRO L
RANGE
N-COUNTER
INTEGER
REGISTER
FRACTIONAL
REGISTER MODULUS
2
25
THIRD-ORDER
FRACTIONAL
INTERPOLATOR RFCP4 RFCP3 RFCP2 RFCP1
CP
LF3
LF2
LDET
TESTLO
TESTLO
IBB
IBB
CCOMP1
CCOMP2
CCOMP3
VTUNE
VOCM
SPI/
I
2
C
INTERFACE
09316-001
RFDIV
Figure 1.
ADRF6850
Rev. 0 | Page 2 of 36
TABLE OF CONTENTS
Features .............................................................................................. 1
Applications ....................................................................................... 1
General Description ......................................................................... 1
Functional Block Diagram .............................................................. 1
Revision History ............................................................................... 2
Specifications ..................................................................................... 3
Timing Characteristics ................................................................ 5
Absolute Maximum Ratings ............................................................ 7
ESD Caution .................................................................................. 7
Pin Configuration and Function Descriptions ............................. 8
Typical Performance Characteristics ........................................... 10
Theory of Operation ...................................................................... 18
Overview ...................................................................................... 18
PLL Synthesizer and VCO ......................................................... 18
Quadrature Demodulator.......................................................... 20
Variable Gain Amplifier (VGA) ............................................... 20
I2C Interface ................................................................................ 20
SPI Interface ................................................................................ 22
Program Modes .......................................................................... 24
Register Map ................................................................................... 26
Register Map Summary ............................................................. 26
Register Bit Descriptions ........................................................... 27
Suggested Power-Up Sequence ..................................................... 30
Initial Register Write Sequence ................................................ 30
Evaluation Board ............................................................................ 31
General Description ................................................................... 31
Hardware Description ............................................................... 31
PCB Schematic............................................................................ 33
PCB Artwork............................................................................... 34
Bill of Materials ........................................................................... 35
Outline Dimensions ....................................................................... 36
Ordering Guide .......................................................................... 36
REVISION HISTORY
10/10—Revision 0: Initial Version
ADRF6850
Rev. 0 | Page 3 of 36
SPECIFICATIONS
VCC = 3.3 V; ambient temperature (TA) = 25°C; ZS = 50 Ω; ZL = 100 Ω differential; PLL loop bandwidth = 50 kHz; REFIN = 13.5 MHz;
PFD = 27 MHz; baseband frequency = 20 MHz, narrow-band mode, unless otherwise noted.
Table 1.
Parameter Test Conditions/Comments Min Typ Max Unit
RF INPUT RFI, RFI, VGAIN pins
Operating Frequency Range 100 1000 MHz
Input P1dB 0 dB gain +12 dBm
60 dB gain −48 dBm
Input IP3 0 dB gain +22.5 dBm
60 dB gain −38 dBm
Input IP2 0 dB gain, single-ended input +40 dBm
60 dB gain, single-ended input −20 dBm
Noise Figure (NF) 0 dB gain 49 dB
<39 dB gain NF rises 1:1 as gain in dB falls
>39 dB gain 11 dB
Maximum Gain ZS = 50 Ω single-ended, ZL = 100 Ω differential 60 dB
Minimum Gain ZS = 50 Ω single-ended, ZL = 100 Ω differential 0 dB
Gain Conformance Error1VGAIN from 200 mV to 1.3 V 0.5 dB
Gain Slope 25 mV/dB
VGAIN Input Impedance 20 kΩ
Return Loss Relative to ZS = 50 Ω, 100 MHz to 1 GHz 15 dB
REFERENCE CHARACTERISTICS REFIN pin
Input Frequency With R divide-by-2 divider enabled 10 300 MHz
With R divide-by-2 divider disabled 10 165 MHz
REFIN Input Sensitivity 0.4 VCC V p-p
REFIN Input Capacitance 10 pF
REFIN Input Current ±100 µA
CHARGE PUMP CP and RSET pins
ICP Sink/Source Programmable
High Value With RSET = 4.7 kΩ 5 mA
Low Value 312.5 µA
Absolute Accuracy With RSET = 4.7 kΩ 2.5 %
VCO
Gain K
VCO
15 MHz/V
SYNTHESIZER SPECIFICATIONS Loop bandwidth = 50 kHz
Frequency Increment 1 Hz
Phase Frequency Detector 10 30 MHz
Spurs
Integer boundary < loop bandwidth −55 dBc
>10 MHz offset from carrier −70 dBc
Phase Noise LO frequency = 1000 MHz
@ 10 Hz offset −75 dBc/Hz
@ 100 Hz offset −80 dBc/Hz
@ 1 kHz offset −90 dBc/Hz
@ 10 kHz offset −98 dBc/Hz
@ 100 kHz offset −110 dBc/Hz
@ 1 MHz offset −136 dBc/Hz
>10 MHz offset −149 dBc/Hz
Integrated Phase Noise 1 kHz to 8 MHz integration bandwidth 0.26 °rms
ADRF6850
Rev. 0 | Page 4 of 36
Parameter Test Conditions/Comments Min Typ Max Unit
Frequency Settling Any step size, maximum frequency error = 1 kHz 260 μs
Maximum Frequency Step for No
Autocalibration
Frequency step with no autocalibration routine;
Register CR24, Bit 0 = 1
100 kHz
BASEBAND OUTPUTS IBB, IBB, QBB, QBB, VOCM pins
Maximum Swing Driving ZL = 100 Ω differential 2.5 V p-p
Common-Mode Range 1.2 1.6 V
Output Impedance Differential 28 Ω
Output DC Offset RFI terminated in ZS = 50 Ω ±20 mV
1 dB Bandwidth
Wideband Mode 250 MHz
Narrow-Band Mode 50 MHz
IQ Balance
Amplitude
Wideband Mode Baseband frequency ≤ 250 MHz ±0.1 dB
Narrow-Band Mode Baseband frequency ≤ 33.2 MHz ±0.1 dB
Phase
Wideband Mode Baseband frequency ≤ 250 MHz ±0.5 Degrees
Narrow-Band Mode Baseband frequency ≤ 33.2 MHz ±0.25 Degrees
IQ Output Impedance Mismatch Baseband frequency = 10 MHz ±0.3 %
Group Delay Variation
Wideband Mode Baseband frequency ≤ 210 MHz 0.25 ns
Baseband frequency ≤ 250 MHz 0.35 ns
Narrow-Band Mode Baseband frequency ≤ 33.2 MHz 0.2 ns
LO to IQ Leakage 1× LO −40 dBm
2× LO −60 dBm
4× LO −60 dBm
RF to IQ Leakage Relative to IQ output level −40 dBc
MONITOR OUTPUT LOMON and LOMON pins
Nominal Output Power −24 dBm
LOGIC INPUTS SDI/SDA, CLK/SCL, CS pins
Input High Voltage, VINH CS 1.4 V
Input Low Voltage, VINL CS 0.6 V
Input High Voltage, VINH SDI/SDA, CLK/SCL 2.1 V
Input Low Voltage, V
INL
SDI/SDA, CLK/SCL 1.1 V
Input Current, IINH/IINL CS, SDI/SDA, CLK/SCL ±1 µA
Input Capacitance, CIN CS, SDI/SDA, CLK/SCL 10 pF
LOGIC OUTPUTS
Output High Voltage, VOH SDO, LDET pins; IOH = 500 μA 2.8 V
Output Low Voltage, VOL SDO, LDET pins; IOL = 500 μA 0.4 V
SDA (SDI/SDA) pins; IOL = 3 mA 0.4 V
POWER SUPPLIES VCC1, VCC2, VCC3, VCC4, VCC5, VCC6, VCC7, VCC8, and
VCC9 pins
Voltage Range 3.15 3.3 3.45 V
Supply Current 350 440 mA
Operating Temperature −40 +85 °C
1 Difference between channel gain and linear fit to channel gain.
ADRF6850
Rev. 0 | Page 5 of 36
TIMING CHARACTERISTICS
I2C Interface Timing
Table 2.
Parameter1Symbol Limit Unit
SCL Clock Frequency fSCL 400 kHz max
SCL Pulse Width High tHIGH 600 ns min
SCL Pulse Width Low t
LOW
1300 ns min
Start Condition Hold Time tHD;STA 600 ns min
Start Condition Setup Time tSU;STA 600 ns min
Data Setup Time tSU;DAT 100 ns min
Data Hold Time tHD; DAT 300 ns min
Stop Condition Setup Time tSU;STO 600 ns min
Data Valid Time tVD;DAT 900 ns max
Data Valid Acknowledge Time tVD;ACK 900 ns max
Bus Free Time tBUF 1300 ns min
1 See Figure 2.
SDA
t
HD;STA
t
SU;DAT
START
CONDITION STOP
CONDITION
S S SP
SCL
1/
f
SCL
t
HIGH
t
LOW
t
HD;DAT
t
VD;DAT AND
t
VD;ACK (ACK SIGNAL ONL Y)
t
BUF
t
SU;STO
t
SU;STA
09316-002
Figure 2. I2C Port Timing Diagram
ADRF6850
Rev. 0 | Page 6 of 36
SPI Interface Timing
Table 3.
Parameter1Symbol Limit Unit
CLK Frequency f
CLK
20 MHz max
CLK Pulse Width High t1 15 ns min
CLK Pulse Width Low t2 15 ns min
Start Condition Hold Time t3 5 ns min
Data Setup Time t4 10 ns min
Data Hold Time t5 5 ns min
Stop Condition Setup Time t6 5 ns min
SDO Access Time t7 15 ns min
CS to SDO High Impedance t8 25 ns max
1 See Figure 3.
t
1
t
3
CS
CLK
SDI
SDO
t
6
t
8
t
7
t
2
t
5
t
4
09316-003
Figure 3. SPI Port Timing Diagram
ADRF6850
Rev. 0 | Page 7 of 36
ABSOLUTE MAXIMUM RATINGS
Table 4. Absolute Maximum Ratings
Parameter Rating
Supply Voltage Pins (VCC1, VCC2, VCC3,
VCC4, VCC5, VCC6, VCC7, VCC8, VCC9)
−0.3 V to +4.0 V
Analog Input/Output −0.3 V to +4.0 V
Digital Input/Output −0.3 V to +4.0 V
RFI, RFI, RFCM 0 V to 3.0 V
θ
(Exposed Paddle Soldered Down) 26°C/W
Maximum Junction Temperature 125°C
Storage Temperature Range −65°C to +150°C
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.
ESD CAUTION
ADRF6850
Rev. 0 | Page 8 of 36
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
PIN 1
INDICATOR
1VCC1 2IBB 3IBB 4QBB 5QBB 6GND 7VOCM 8
GND 9RSET 10LF3 11CP 12LF2 13VCC2 14VCC3
35 CCOMP3
36 VCC7
37 GND
38 VTUNE
39 MUXOUT
40 LDET
41 GND
42 VCC8
34 CCOMP2
33 CCOMP1
32 GND
31 VCC6
30 CLK/SCL
29 SDI/SDA
15VCC4 16VCC5 17REFIN
19GND
21GND 20GND
22TESTLO 23TESTLO 24GND 25LOMON 26LOMON 27CS 28SDO
18
REFIN
45 GND
46 GND
47 GND
48 GND
49 VCC9
50 GND
51 RFI
52 GND
53 RFCM
54 GND
44 GND
43 VGAIN
TOP VI EW
(No t t o Scale)
ADRF6850
55 RFI
56 GND
NOTES
1. CONNECT EX P OSED PAD TO GROUND PLANE V IA
A LOW IM P E DANCE P ATH.
09316-004
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin No. Mnemonic Description
1, 13, 14, 15, 16,
31, 36, 42, 49
VCC1 to VCC9 Positive Power Supplies. Apply a 3.3 V power supply to all VCCx pins. Decouple each pin with a power
supply decoupling capacitor.
6, 8, 19, 20, 21,
24, 32, 37, 41,
44, 45, 46, 47,
48, 50, 52, 54, 56
GND Analog Ground. Connect to a low impedance ground plane.
2, 3, 4, 5 IBB, IBB, QBB,
QBB
Differential In-Phase and Quadrature Baseband Outputs. These low impedance outputs can drive
2.5 V p-p into 100 Ω differential loads.
7 VOCM Baseband Common-Mode Voltage Input. When ac coupling the baseband output pins, ground
VOCM. There is an option to apply an external voltage, which may be relevant when dc coupling the
baseband output pins. Note that Register CR29, Bit 6 must be set accordingly.
33 CCOMP1 Internal Compensation Node. This pin must be decoupled to ground with a 100 nF capacitor.
34 CCOMP2 Internal Compensation Node. This pin must be decoupled to ground with a 100 nF capacitor.
35 CCOMP3 Internal Compensation Node. This pin must be decoupled to ground with a 100 nF capacitor.
38 VTUNE Control Input to the VCO. This voltage determines the output frequency and is derived from filtering
the CP output voltage.
9 RSET Charge Pump Current Set. Connecting a resistor between this pin and ground sets the maximum
charge pump output current. The relationship between ICP and RSET is
SET
CPmax
R
I5.23
=
where RSET = 4.7 kΩ and ICP max = 5 mA.
11 CP Charge Pump Output. When enabled, this provides ±ICP to the external loop filter, which in turn,
drives the internal VCO.
27 CS Chip Select. CMOS input. When CS is high, the data stored in the shift registers is loaded into one of
the 31 registers. In I2C mode, when CS is high, the slave address of the device is 0x78, and when CS is
low, the slave address is 0x58.
29 SDI/SDA Serial Data Input for SPI Port, Serial Data Input/Output for I2C Port. In SPI mode. This input is a high
impedance CMOS data input, and data is loaded in an 8-bit word. In I2C mode, this pin is a
bidirectional port.
30 CLK/SCL Serial Clock Input for SPI/I2C Port. This serial clock is used to clock in the serial data to the registers.
This input is a high impedance CMOS input.
28 SDO Serial Data Output for SPI Port. Register states can be read back on the SDO data output line in an
8-bit word.
17 REFIN Reference Input. AC couple this high impedance CMOS input.
18 REFIN Reference Input Bar. Ground this pin.
ADRF6850
Rev. 0 | Page 9 of 36
Pin No. Mnemonic Description
51, 55 RFI, RFI RF Inputs. 50 Ω internally biased RF inputs. For single-ended operation, RFI must be ac-coupled to
the source, and RFI must be ac-coupled to the ground plane.
53 RFCM RF Input Common Mode. Connect to RFI when driving the input in single-ended mode. When driving
the input differentially using a balun, connect this pin to the common terminal of the output coil of
the balun. Decouple RFCM to the ground plane.
25, 26 LOMON,
LOMON
Differential Monitor Outputs. These pins provide a replica of the internal local oscillator frequency
(1× LO) at four different power levels: −6 dBm, −12 dBm, −18 dBm, and −24 dBm, approximately.
These open-collector outputs must be terminated with external resistors to VCCx. These outputs can
be disabled through serial port programming and should be connected to VCCx if not used.
10, 12 LF3/LF2 Extra Loop Filter Pins for Fastlock. Use these pins to reduce lock time.
40 LDET Lock Detect. This pin provides an active high output when the PLL frequency is locked. The lock
detect timing is controlled by Register CR14 (Bit 7) and Register CR23 (Bit 3).
39 MUXOUT Muxout. This output is a test output for diagnostic use only. Allow this pin to remain open circuit.
22, 23 TESTLO, TESTLO Differential Test Inputs. For internal use only. These pins should be grounded.
43 VGAIN VGA Gain Input. Drive this pin by a voltage in the range from 0 V to 1.5 V. This voltage controls the
gain of the VGA. A 0 V input sets the VGA gain to 0 dB, whereas a 1.5 V input sets the VGA gain to
+60 dB if the VGA Gain Mode Polarity Bit CR30, Bit 2, is set to 0. If the VGA gain mode polarity bit is
set to 1, a 0 V input sets the VGA gain to +60 dB, whereas a 1.5 V input sets the VGA gain to 0 dB.
EP Exposed Paddle. Connect the exposed pad to the ground plane via a low impedance path.
ADRF6850
Rev. 0 | Page 10 of 36
TYPICAL PERFORMANCE CHARACTERISTICS
A nominal condition is defined as 25°C, 3.30 V, and worst-case frequency. A worst-case condition is defined as having the worst-case
temperature, supply voltage, and frequency.
–60
–50
–40
–30
–20
–10
0
10
20
IP 1dB (dBm)
CHANNEL G AIN (dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
09316-011
0605040302010
Figure 5. Input 1dB Compression Point (IP1dB) vs. Channel Gain, and RF
Input Frequency, Nominal Conditions, Narrow-Band Mode
–60
–50
–40
–30
–20
–10
0
10
20
IP 1dB (dBm)
CHANNEL G AIN (dB)
3.30V, 25°C
3.15V, –40°C
3.45V, –40°C
3.15V, 85°C
3.45V, 85°C
09316-012
0605040302010
Figure 6. Input 1dB Compression Point (IP1dB) vs. Channel Gain, Supply, and
Temperature, RF Input Frequency = 100 MHz, Narrow-Band Mode
–60
–50
–40
–30
–20
–10
0
10
20
010 20 30 40 50 60
IP 1dB (dB)
CHANNEL GAI N ( dB)
3.30V , +25°C
3.15V , –40°C
3.45V , –40°C
3.15V , +85°C
3.45V , +85°C
09316-034
Figure 7. Input 1dB Compression Point (IP1dB) vs. Channel Gain, Supply, and
Temperature, RF Input Frequency = 1000 MHz, Narrow-Band Mode
0
5
10
15
20
25
30
35
40
45
50
OCCURRENCE (%)
INP UT P1dB AT CHANNEL GAIN O F 0dB (dBm)
NOMINAL
WORST-CASE
09316-008
13.413.012.612.211.811.411.010.610.29.89.49.08.6
Figure 8. Input 1dB Compression Point (IP1dB) Distribution with Channel
Gain = 0 dB at Nominal and Worst-Case Conditions
0
5
10
15
20
25
30
35
40
45
50
55
60
OCCURRENCE (%)
INP UT P1dB AT CHANNEL GAIN O F 60dB (dBm)
NOMINAL
WORST-CASE
09316-009
–46.8
–47.2
–47.6
–48.0
–48.4
–48.8
–49.2
–49.6
–50.0
–50.4
Figure 9. Input 1dB Compression Point (IP1dB) Distribution with Channel
Gain = 60 dB at Nominal and Worst-Case Conditions
–60
–50
–40
–30
–20
–10
0
10
20
–10 010 20 30 40 50 60 70
IP 1dB (dBm)
CHANNEL GAI N ( dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
09316-033
Figure 10. Input 1dB Compression Point (IP1dB) vs. Channel Gain, and RF
Input Frequency, VOCM = 1.2 V, Nominal Conditions, Narrow-Band Mode
ADRF6850
Rev. 0 | Page 11 of 36
–60
–50
–40
–30
–20
–10
0
10
20
–10 010 20 30 40 50 60 70
IP 1dB (dBm)
CHANNEL GAI N ( dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
09316-057
Figure 11. Input 1dB Compression Point (IP1dB) vs. Channel Gain, and RF
Input Frequency, VOCM = 1.6 V, Nominal Conditions, Narrow-Band Mode
–60
–50
–40
–30
–20
–10
0
10
20
IP 1dB (dBm)
CHANNEL G AIN (dB)
IQ = 20MHz
IQ = 50MHz
IQ = 100MHz
IQ = 200MHz
IQ = 250MHz
09316-010
0605040302010
Figure 12. Input 1dB Compression Point (IP1dB) vs. Channel Gain, and IQ
Output Frequency, LO = 1000 MHz, Nominal Conditions, Wideband Mode
–50
–40
–30
–20
–10
0
10
20
30
INP UT IP3 (dBm)
CHANNEL G AIN (dB)
09316-015
060 705040302010
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
Figure 13. Input IP3 vs. Channel Gain, and RF Input Frequency,
Nominal Conditions
–50
–40
–30
–20
–10
0
10
20
30
INP UT IP3 (dBm)
CHANNEL G AIN (dB)
09316-016
060 705040302010
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
Figure 14. Input IP3 vs. Channel Gain, and RF Input Frequency,
Worst-Case Conditions
0
10
20
30
40
50
60
70
19.6 20.0 20.4 20.8 21.2 21.6 22.0 22.4 22.8 23.2 23.6 24.0
OCCURRE NCE ( %)
IIP3 AT CHANNEL GAI N = 0dB (dBm)
NOMINAL
WORST-CASE
09316-035
Figure 15. Input IP3 Distribution with Channel Gain = 0 dB at Nominal and
Worst-Case Conditions
0
5
10
15
20
25
30
35
–40.0–40.4 –39.6 –39.2 –38.8 –38.4 –38.0 –37.6 –37.2 –36.8 –36.4 –36.0
OCCURRE NCE ( %)
IIP3 AT CHANNE L G AIN = 60dB (dBm)
NOMINAL
WORST-CASE
09316-036
Figure 16. Input IP3 Distribution with Channel Gain = 60 dB at Nominal and
Worst-Case Conditions
ADRF6850
Rev. 0 | Page 12 of 36
–50
–40
–30
–20
–10
0
10
20
30
–10 010 20 30 40 50 60 70
INP UT IP3 (dBm)
CHANNEL GAI N ( dB)
IQ FREQ UE NCIES = 16M Hz AND 19M Hz
IQ FREQ UE NCIES = 46M Hz AND 49M Hz
IQ FREQ UE NCIES = 96M Hz AND 99M Hz
IQ FREQ UE NCIES = 196M Hz AND 199M Hz
IQ FREQ UE NCIES = 246M Hz AND 249M Hz
09316-037
Figure 17. Input IP3 vs. Channel Gain, and IQ Output Frequency,
Wideband Mode, Nominal Conditions
–50
–40
–30
–20
–10
0
10
20
30
–10 010 20 30 40 50 60 70
INP UT IP3 (dBm)
CHANNEL GAI N ( dB)
IQ FREQ UE NCIES = 16M Hz AND 19M Hz
IQ FREQ UE NCIES = 46M Hz AND 49M Hz
IQ FREQ UE NCIES = 96M Hz AND 99M Hz
IQ FREQ UE NCIES = 196M Hz AND 199M Hz
IQ FREQ UE NCIES = 246M Hz AND 249M Hz
09316-038
Figure 18. Input IP3 vs. Channel Gain, and IQ Output Frequency,
Wideband Mode, Worst-Case Conditions
–20
–10
0
10
20
30
40
50
60
70
INP UT IP2 (dBm)
CHANNEL G AIN (dB)
09316-013
–10 070605040302010
DIRECT IIP2
DOWN-CONVE RTED IIP2
Figure 19. Input IP2 vs. Channel Gain, Wideband Mode, Nominal Conditions
–20
–30
–10
0
10
20
30
40
50
60
70
INP UT IP2 (dBm)
CHANNEL G AIN (dB)
09316-014
–10 070605040302010
DIRECT IIP2
DOWN-CONVE RTED IIP2
Figure 20. Input IP2 vs. Channel Gain, Wideband Mode,
Worst-Case Conditions
09316-023
0
10
20
30
40
50
60
010 20 30 40 50 60 70
NOISE FIGURE (dB)
CHANNEL GAI N ( dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
Figure 21. Noise Figure vs. Channel Gain, and RF Input Frequency,
Narrow-Band Mode, Nominal Conditions
09316-024
0
10
20
30
40
50
60
010 20 30 40 50 60 70
NOISE FIGURE (dB)
CHANNEL GAI N ( dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
Figure 22. Noise Figure vs. Channel Gain, and RF Input Frequency,
Narrow-Band Mode, Worst-Case Conditions
ADRF6850
Rev. 0 | Page 13 of 36
0
10
20
30
40
50
60
010 20 30 40 50 60 70
NOISE FIGURE (dB)
CHANNEL GAI N ( dB)
09316-045
Figure 23. Noise Figure Distribution vs. Channel Gain, Narrow-Band Mode,
Nominal Conditions
0
10
20
30
40
50
60
010 20 30 40 50 60 70
NOISE FIGURE (dB)
CHANNEL GAI N ( dB)
09316-046
Figure 24. Noise Figure Distribution vs. Channel Gain, Narrow-Band Mode,
Worst-Case Conditions
09316-025
0
10
20
30
40
50
60
010 20 30 40 50 60 70
NOISE FIGURE (dB)
CHANNEL GAI N ( dB)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
Figure 25. Noise Figure vs. Channel Gain, and RF Input Frequency,
Wideband Mode, Nominal Conditions
–10
0
10
20
30
40
50
60
70
CHANNEL GAI N ( dB)
VGAIN (V)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
09316-007
00.2 0.4 0.6 0.8 1.0 1.2 1.4
Figure 26. Channel Gain vs. VGAIN and RF Input Frequency,
Nominal Conditions
0
10
20
30
40
50
60
59.6
59.8
60.0
60.2
60.4
60.6
60.8
61.0
61.2
61.4
61.6
61.8
62.0
62.2
OCCURRE NCE ( %)
CHANNEL GAI N RANGE (d B)
NOMINAL
WORST-CASE
09316-006
Figure 27. Channel Gain Range Distribution at Nominal and
Worst-Case Conditions
09316-021
100 200 300 400 500 600 700 800 900 1000
CHANNEL GAI N ( dB)
RF INPUT F RE QUENCY (MHz)
–2.0
–1.5
–1.0
–0.5
0
0.5
1.0 3.30V, 25°C
3.15V, –40°C
3.45V, –40°C
3.15V, 85°C
3.45V, 85°C
Figure 28. Minimum Channel Gain vs. RF Input Frequency,
Supply, and Temperature
ADRF6850
Rev. 0 | Page 14 of 36
0
5
10
15
20
25
30
OCCURRE NCE ( %)
MI NIMUM CHANNEL GAI N ( dB)
NOMINAL
WORST-CASE
09316-019
–2.0
–2.2
–1.8
–1.6
–1.4
–1.2
–1.0
–0.8
–0.6
–0.4
–0.2
0.2
0.4
0.6
0.8
1.0
1.2
0
Figure 29. Minimum Channel Gain Distribution at Nominal and
Worst-Case Conditions
09316-018
MAXIMUM CHANNEL GAIN (dB)
3.30V, 25°C
3.15V, –40°C
3.45V, –40°C
3.15V, 85°C
3.45V, 85°C
60.0
60.5
61.0
61.5
62.0
62.5
63.0
100 200 300 400 500 600 700 800 900 1000
RF INPUT F RE QUENCY (MHz)
Figure 30. Maximum Channel Gain vs. RF Input Frequency,
Supply, and Temperature
0
5
10
15
20
25
OCCURRE NCE ( %)
MAXIMUM CHANNEL GAIN (dB)
NOMINAL
WORST-CASE
09316-017
62.2
62.0
61.8
61.6
61.4
61.2
61.0
60.8
60.6
60.4
60.2
60.0
59.8
59.6
Figure 31. Maximum Channel Gain Distribution at Nominal and
Worst-Case Conditions
–3
–2
–1
0
1
2
3
CHANNEL GAI N CONFO RM ANCE E RROR (dB)
VGAIN (V)
RF = 100M Hz
RF = 300M Hz
RF = 550M Hz
RF = 800M Hz
RF = 1000M Hz
09316-005
00.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5
Figure 32. Channel Gain Conformance Error vs. VGAIN and RF Input Frequency,
Nominal Conditions
–35
–30
–25
–20
–15
–10
–5
0
100 200 300 400 500 600 700 800 900 1000
RET URN LOSS ( dB)
RF INPUT F RE QUENCY (MHz)
V
GAIN
= 0V
V
GAIN
= 0.5V
V
GAIN
= 1.0V
V
GAIN
= 1.5V
09316-039
Figure 33. Input Return Loss vs. RF Input Frequency and Channel Gain,
Nominal Conditions
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
100 200 300 400 500 600 700 800 900 1000
INTEGER BOUNDARY SPURS (d Bc)
LO FREQUENCY (MHz)
INTEGER BOUNDARY SPUR AT 9.6kHz O FFSE T
INTEGER BOUNDARY SPUR AT 19.2kHz O FFSE T
INTEGER BOUNDARY SPUR AT 38.4kHz O FFSE T
09316-044
Figure 34. Integer Boundary Spurs vs. LO Frequency, Channel Gain,
Supply, and Temperature
ADRF6850
Rev. 0 | Page 15 of 36
REF E RE NCE S P UR ( dBc)
–120
–100
–80
–60
–40
–20
0
100 200 300 400 500 600 700 800 900 1000
LO FREQUENCY (MHz)
V
GAIN
= 1.5V
V
GAIN
≤ 1.0V
09316-049
Figure 35. Reference Spurs at 13.5 MHz from Carrier vs. LO Frequency,
Channel Gain, Supply, and Temperature
–120
–100
–80
–60
–40
–20
0
100 200 300 400 500 600 700 800 900 1000
PF D S P UR ( dBc)
LO FREQUENCY (MHz)
VGAIN = 1.5V
VGAIN ≤ 1.0V
09316-048
Figure 36. PFD Spurs at 27 MHz from Carrier vs. LO Frequency, Channel Gain,
Supply, and Temperature
–170
–160
–150
–140
–130
–120
–110
–100
–90
–80
–70
–60
10 100 1k 10k 100k 1M 10M
PHASE NOISE (d Bc/Hz)
OFFSET FREQUENCY (Hz)
TABLE OF DI S TRIBUTIO N DAT A:
OFF SET FREQUENCY (Hz): 10 100 1k 10k 100k 1M 10M
TYPI CAL RANGE ( d Bc/Hz ) : –91/–100 –99/–111 –107/–115 –118/–121 –129/–132 –150/–154 –151/–153
WORST- CAS E RANGE ( d Bc/Hz ) :–90/–105 –95/–108 –105/–116 –118/–121 –128/–131 –151/–154 –151/–153
09316-052
Figure 37. Phase Noise Performance Including Distribution Table at LO
Frequency = 100 MHz at Nominal and Worst-Case Conditions
10 100 1k 10k 100k 1M 10M
PHASE NOISE (d Bc/Hz)
OFFSET FREQUENCY (Hz)
–160
–150
–140
–130
–120
–110
–100
–90
–80
–70
–60
TABLE OF DI S TRIBUTIO N DAT A:
OFF SET FREQUENCY (Hz): 10 100 1k 10k 100k 1M 10M
TYPI CAL RANGE ( d Bc/Hz ) : –75/–85 –78/–89 –84/–95 –97/–100 –110/–113 –136/–138 –149/–153
WORST- CAS E RANGE ( d Bc/Hz ) : –72/–82 –74/–89 –89/–96 –97/–100 –110/–112 –136/–138 –149/–152
09316-051
Figure 38. Phase Noise Performance Including Distribution Table at LO
Frequency = 1000 MHz at Nominal and Worst-Case Conditions
0
0.1
0.2
0.3
0.4
100 200 300 400 500 600 700 800 900 1000
RMS JITTE R ( Degrees)
LO FREQUENCY (MHz)
3.30V ; +25°C
3.15V ; +85°C
3.45V ; +85°C
3.15V ; –40°C
3.45V ; –40°C
09316-041
Figure 39. Integrated Phase Noise vs. LO Frequency, Supply, and
Temperature
0
5
10
15
20
25
30
0.19 0.21 0.23 0.25 0.27 0.29 0.31 0.33
OCCURRE NCE ( %)
RMS JITTE R ( Degrees)
NOMINAL
WORST-CASE
09316-040
Figure 40. Integrated Phase Noise Distribution with LO Frequency =
1000 MHz at Nominal and Worst-Case Conditions
ADRF6850
Rev. 0 | Page 16 of 36
–50 050 100 150 200 250 300 350 400 450 500 550
ERRO R FREQUENCY (Hz)
START OF ACQUISITION
ON CR0 WRITE
CR23[3] = 1
CR23[3] = 0
ACQUISITION
TO 1kHz
BEST CASE
TYPICAL
WORST CASE
LDET
LDET
1
0.1
0.01
10
100
1k
10k
100k
1M
10M
100M
1G
TIME (µs)
09316-055
Figure 41. PLL Frequency Settling Time with Typical, Best-Case, and Worst-
Case Frequency Hop with Lock Detect Shown, Nominal Conditions
0
2
4
6
8
10
12
14
16
18
20
–18 –14 –10 –6 –2 2 6 10 14 18 22 26 30
OCCURRE NCE ( %)
OUTPUT DC OFFSET (mV)
I OUTPUT
Q OUTPUT
09316-050
Figure 42. Output DC Offset Distribution for I and Q Outputs,
Nominal Conditions
–30
–25
–20
–15
–10
–5
0
5
0.1 110 100 1000
OUTPUT POWER (dB)
IQ OUTPUT FREQUENCY (MHz)
WB M ODE
NB MO DE = 50M Hz
NB MO DE = 43M Hz
NB MO DE = 37M Hz
NB MO DE = 30M Hz
09316-047
Figure 43. Normalized IQ Output Bandwidth, Narrow-Band, and
Wideband Modes, Nominal Conditions
09316-031
0
5
10
15
20
25
30
0.005
0
0.010
0.015
0.020
0.025
0.030
0.035
0.040
0.045
0.050
0.055
0.060
0.065
0.070
0.075
0.080
0.085
0.090
0.095
0.100
OCCURRE NCE ( %)
ABSOLUTE IQAMPLITUDE BALANCE (d B)
Figure 44. Absolute IQ Amplitude Balance, Narrow-Band Mode,
Nominal Conditions
0
2
4
6
8
10
12
14
16
18
20
–0.45 –0.35 –0.25 –0.15 –0.05 0.05 0.15 0.25 0.35 0.45
OCCURRE NCE ( %)
IQ PHASE BAL ANCE ( Degrees)
09316-042
Figure 45. IQ Phase Balance, Narrow-Band Mode, Nominal Conditions
09316-026
–100
–90
–80
–70
–60
–50
–40
–30
–20
–10
0
V
GAIN
= 1.5V
200100 300 400 500 600 700 800 900 1000
1× LO FEEDTHROUG H ( dBm)
LO FREQUENCY (MHz)
V
GAIN
= 0V, 0.5V, 1V
Figure 46. 1× LO Feedthrough vs. LO Frequency, VGAIN, Supply, and
Temperature (Narrow-Band Mode)
ADRF6850
Rev. 0 | Page 17 of 36
09316-029
–80
–100
–120
–60
–40
–20
0
100 200 300 400 500 600 700 800 900 1000
2× LO FEEDTHROUG H ( dBm)
LO FREQUENCY (MHz)
Figure 47. 2× LO Feedthrough vs. LO Frequency, VGAIN, Supply, and
Temperature (Narrow-Band Mode)
09316-030
–80
–100
–120
–60
–40
–20
0
4× LO FEEDTHROUG H ( dBm)
100 200 300 400 500 600 700 800 900 1000
LO FREQUENCY (MHz)
Figure 48. 4× LO Feedthrough vs. LO Frequency, VGAIN, Supply, and
Temperature (Narrow-Band Mode)
09316-020
–46.5
–46.0
–45.5
–45.0
–44.5
–44.0
–43.5
–43.0
–42.5
–42.0
–41.5
–41.0
–40.5
–40.0
–39.5
–39.0
–38.5
–38.0
–37.5
–37.0
–36.5
–36.0
0
5
10
15
20
25
OCCURRE NCE ( %)
1× LO FEEDTHOUGH (dBm)
NOMINAL
WORST-CASE
Figure 49. 1× LO Feedthrough Distribution at Nominal and Worst-Case
Conditions with LO Frequency > 300 MHz,
Narrow-Band Mode
09316-022
–120
–100
–80
–60
–40
–20
0
330 430 530 630 730 830 930
1× LO FEE DTHROUG H ( dBm)
LO FREQUENCY (MHz)
V
GAIN
= 0V, 0.5V, 1V
V
GAIN
= 1.5V
V
GAIN
= 1.3V
Figure 50. 1× LO Feedthrough vs. LO Frequency, VGAIN, Supply, and
Temperature, Fourth-Order Filter at 300 MHz Applied, Wideband Mode
09316-028
–80
–100
–120
–60
–40
–20
0
V
GAIN
= 1.5V
V
GAIN
= 0V, 0.5V, 1V
100 200 300 400 500 600 700 800 900 1000
1× RF TO IQ LEAKAGE (dBc)
RF FREQUENC Y (MHz)
Figure 51. 1× RF Feedthrough vs. RF Input Frequency, VGAIN, Supply, and
Temperature, Narrow-Band Mode
09316-027
–140
–80
–100
–120
–60
–40
–20
0
VGAIN = 1.5V
VGAIN = 1.0V
VGAIN = 1.3V
VGAIN = 0V, 0.5V, 1V
330 430 530 630 730 830 930
1× RF TO IQ LEAKAGE (dBc)
RF FREQUENC Y (MHz)
Figure 52. 1× RF Feedthrough vs. RF Input Frequency, VGAIN, Supply, and
Temperature, Fourth-Order Filter at 300 MHz Applied, Wideband Mode
ADRF6850
Rev. 0 | Page 18 of 36
THEORY OF OPERATION
OVERVIEW
The ADRF6850 device can be separated into the following basic
building blocks:
• PLL synthesizer and VCO
• Quadrature demodulator
• Variable gain amplifier (VGA)
• I2C/SPI interface
Each of these building blocks is described in detail in the
sections that follow.
PLL SYNTHESIZER AND VCO
Overview
The phase-locked loop (PLL) consists of a fractional-N frequency
synthesizer with a 25-bit fixed modulus, allowing a frequency
resolution of less than 1 Hz over the entire frequency range. It
also has an integrated voltage controlled oscillator (VCO) with
a fundamental output frequency ranging from 2000 MHz to
4000 MHz. An RF divider, controlled by Register CR28, Bits[2:0],
extends the lower limit of the frequency range to less than
400 MHz. This 400 MHz to 4000 MHz frequency output is
then applied to a divide-by-4 quadrature circuit to provide a
local oscillator (LO) ranging from 100 MHz to 1000 MHz to the
quadrature demodulator.
Reference Input Section
The reference input stage is shown in Figure 53. SW1 and SW2
are normally closed switches. SW3 is normally open. When
power-down is initiated, SW3 is closed, and SW1 and SW2 are
open. This ensures that there is no loading of the REFIN pin at
power-down.
BUFFER
TO
R-DIVIDER
REFIN
100kΩ
NC
SW2
SW3
NC
NC
SW1
POWER-DOWN
CONTROL
09316-060
Figure 53. Reference Input Stage
Reference Input Path
The on-chip reference frequency doubler allows the input
frequency of the reference signal to be doubled. This is useful
for increasing the PFD comparison frequency. Making the PFD
frequency higher improves the noise performance of the system.
Doubling the PFD frequency usually improves the in-band phase
noise performance by 3 dBc/Hz.
The 5-bit R-divider allows the input reference frequency
(REFIN) to be divided down to produce the reference clock
to the PFD. Division ratios from 1 to 32 are allowed.
An additional divide-by-2 (÷2) function in the reference input
path allows for a greater division range.
×2
DOUBLER 5-BIT
R-DIVIDER
FROM
REFIN
PIN
TO
PFD
÷2
09316-061
Figure 54. Reference Input Path
The PFD frequency equation is
fPFD = fREFIN × [(1 + D)/(R × (1 + T))] (1)
where:
fREFIN is the reference input frequency.
D is the doubler bit.
R is the programmed divide ratio of the binary 5-bit
programmable reference divider (1 to 32).
T is the ÷2 bit (0 or 1).
RF Fractional-N Divider
The RF fractional-N divider allows a division ratio in the PLL
feedback path that can range from 23 to 4095. The relationship
between the fractional-N divider and the LO frequency is
described in the following section.
INT and FRAC Relationship
The integer (INT) and fractional (FRAC) values make it
possible to generate output frequencies that are spaced by
fractions of the phase frequency detector (PFD) frequency.
See the Programming the Correct LO Frequency section for
more information.
The LO frequency equation is
LO = fPFD × (INT + (FRAC/225))/2 × 2RFDIV (2)
where:
LO is the local oscillator frequency.
fPFD is the PFD frequency.
INT is the integer component of the required division factor
and is controlled by the CR6 and CR7 registers.
FRAC is the fractional component of the required division
factor and is controlled by the CR0 to CR3 registers.
RFDIV is the setting in Register CR28, Bits[2:0], and controls
the setting of a divider at the output of the PLL.
N-COUNTER
INT
REG
TO
PFD
RF N- DIVIDER N = INT + FRAC/2
25
FROM VCO
OUTPUT
DIVIDERS
FRAC
VALUE
THIRD-ORDER
FRACTIONAL
INTERPOLATOR
09316-062
Figure 55. RF Fractional-N Divider
Phase Frequency Detector (PFD) and Charge Pump
The PFD takes inputs from the R-divider and the N-counter and
produces an output proportional to the phase and frequency differ-
ence between them (see Figure 56 for a simplified schematic).
The PFD includes a fixed delay element that sets the width of
the antibacklash pulse, ensuring that there is no dead zone in
the PFD transfer function.
ADRF6850
Rev. 0 | Page 19 of 36
U3
CLR2
Q2D2
U2
DOWN
UP
HI
HI
CP
–IN
+IN
CHARGE
PUMP
DELAY
CLR1
Q1D1
U1
09316-063
Figure 56. PFD Simplified Schematic
Lock Detect (LDET)
LDET (Pin 40) signals when the PLL has achieved lock to an
error frequency of less than 1 kHz. On a write to Register CR0,
a new PLL acquisition cycle starts, and the LDET signal goes
low. When lock has been achieved, this signal returns high.
Voltage Controlled Oscillator (VCO)
The VCO core in the ADRF6850 consists of three separate VCOs,
each with 16 overlapping bands. This configuration of 48 bands
allows the VCO frequency range to extend from 2000 MHz to
4000 MHz. The three VCOs are divided externally by a program-
mable divider (RFDIV controlled by Register CR28, Bits[2:0]).
This divider provides divisions of 1, 2, 4, and 8 to ensure that the
frequency range is extended from 250 MHz (2000 MHz/8) to
4000 MHz (4000 MHz/1). A lower limit of only 400 MHz is
required. A divide-by-4 quadrature circuit provides the full LO
frequency range from 100 MHz to 1000 MHz. Figure 57 shows
a sweep of VTUNE vs. LO frequency demonstrating the three VCOs
overlapping and the multiple overlapping bands within each
VCO at the LO frequency range of 100 MHz to 1000 MHz. Note
that this plot includes the RFDIV divider being incorporated to
provide further divisions of the fundamental VCO frequency;
thus, each VCO is used on four different occasions throughout the
full LO frequency range. The choice of three 16-band VCOs and
an RFDIV divider allows the wide frequency range to be covered
without large VCO sensitivity (KVCO) or resultant poor phase
noise and spurious performance.
0.9
1.1
1.3
1.5
1.7
1.9
2.1
2.3
2.5
100 200 300 400 500 600 700 800 900 1000
V
TUNE
(V)
LO FREQUENCY (MHz)
09316-056
Figure 57. VTUNE vs. LO Frequency
The correct VCO and band are chosen automatically by the
VCO and band select circuitry when Register CR0 is updated.
This is referred to as autocalibration. The autocalibration time
is set by Register CR25.
Autocalibration Time = (BSCDIV × 24)/PFD (3)
where:
BSCDIV = Register CR25, Bits[7:0].
PFD = PFD frequency.
For a PFD frequency of 27 MHz, BSCDIV = 112 to set an
autocalibration time of 100 µs.
Note that BSCDIV must be recalculated if the PFD frequency is
changed. The recommended autocalibration setting is 100 µs.
During this time, the VCO VTUNE is disconnected from the output
of the loop filter and is connected to an internal reference voltage.
A typical frequency acquisition is shown in Figure 58.
1
10
100
1k
10k
100k
1M
10M
100M
1G
050 100 150 200 250 300 350 400 450 500
FREQUENCY ERROR (Hz)
TIME (µs)
ACQUISITION TO 1kHz
AUTOCAL
TIME (µs)
09316-054
Figure 58. PLL Acquisition
After autocalibration, normal PLL action resumes, and the
correct frequency is acquired to within a frequency error of
1 kHz in 260 μs typically. For a maximum cumulative step of
100 kHz, autocalibration can be turned off by Register CR24,
Bit 0. This enables cumulative PLL acquisitions of 100 kHz or
less to occur without the autocalibration procedure, which
improves acquisition times significantly (see Figure 59).
1
10
100
1k
10k
100k
1M
10M
100M
1G
020 40 60 80 100 120 140 160 180 200
FREQUENCY ERROR (Hz)
TIME (µs)
ACQUISITION TO 1kHz
09316-053
Figure 59. PLL Acquisition Without Autocalibration for a 100 kHz Step
ADRF6850
Rev. 0 | Page 20 of 36
The VCO displays a variation of KVCO as VTUNE varies within
the band and from band to band. Figure 60 shows how the
KVCO varies across the fundamental LO frequency range from
500 MHz to 1000 MHz. Note that KVCO is shown at the LO
frequency rather than at the VCO frequency. Figure 60 is useful
when calculating the loop filter bandwidth and individual loop
filter components using ADISimPLL™. ADISimPLL is an
Analog Devices, Inc., simulator that aids in PLL design,
particularly with respect to the loop filter. It reports parameters
such as phase noise, integrated phase noise, acquisition time,
and so forth for a particular set of input conditions.
ADISimPLL can be downloaded from www.analog.com.
0
5
10
15
20
25
500 550 600 650 700 750 800 850 900 950 1000
LO FREQUENCY (MHz)
VCO SENSITIVI TY (MHz/V)
09316-059
Figure 60. KVCO vs. LO Frequency
Programming the Correct LO Frequency
There are two steps to programming the correct LO frequency.
The user can calculate the N-divider ratio that is required in the
PLL and the RFDIV value based on the required LO frequency
and PFD frequency.
1. Calculate the value of RFDIV, which is used to program
Register CR28, Bits[2:0], from the following lookup table
(Table 6). See also Table 24.
Table 6. RFDIV Lookup Table
LO Frequency (MHz) RFDIV = Register CR28[2:0]
500 to 1000 000 = divide-by-1
250 to 500 001 = divide-by-2
125 to 250 010 = divide-by-4
100 to 125 011 = divide-by-8
2. Using the following equation, calculate the value of the
N-divider:
N = (2RFDIV × 2 × LO)/(fPFD) (4)
where:
N is the N-divider value.
RFDIV is the setting in Register CR28, Bits[2:0].
LO is the local oscillator frequency.
fPFD is the PFD frequency.
This equation is a different representation of Equation 2.
Example to Program the Correct LO Frequency
Assume that the PFD frequency is 27 MHz and the required LO
frequency is 330 MHz.
Step 1. From Table 6, 2RFDIV = 2.
Step 2. N = (2 × 2 × 330E+6)/(27E+6) = 48.88888889.
The N-divider value is composed of integer (INT) and
fractional (FRAC) components according to the following
equation:
N = INT + FRAC/225 (5)
INT = 48 and FRAC = 29,826,162.
The appropriate registers must then be programmed according to
the register map, ensuring that Register CR0 is the last register
to be programmed because this write starts a new PLL acquisi-
tion cycle.
QUADRATURE DEMODULATOR
The quadrature demodulator can be powered up by Register CR29,
Bit 0. It has an output filter with narrow-band and wideband
modes, which are selected by Register CR29, Bit 3. Wideband
mode has a 1 dB filter cutoff of 250 MHz. Narrow-band mode
has selectable cutoff filters of 30 MHz through 50 MHz by pro-
gramming Register CR29, Bits[5:4]. A dc bias voltage of 1.4 V
(VOCM) can be set internally by setting Register CR29, Bit 6 = 1.
To select an external dc bias voltage, set Register CR29, Bit 6 = 0,
and drive Pin 7, VOCM, with the requisite external bias voltage.
VARIABLE GAIN AMPLIFIER (VGA)
The variable gain amplifier (VGA) at the input to the demodulator
can be driven either single-ended or differentially.
To drive single-ended, connect Pin 53, RFCM, to Pin 51, RFI,
and decouple both pins to ground with a 10 nF capacitor. Drive
the input signal through Pin 55, RFI.
To drive differentially, use a balun with the RFI and RFI pins
driven by the balanced outputs of the balun, and connect the
RFCM pin to the common balun output terminal. Decouple
RFCM to ground.
The VGA gain range is approximately 60 dB and is achieved by
varying the VGAIN voltage from 0 V to 1.5 V. The Typical
Performance Characteristics section has more information on
the VGA gain performance. A 0 V input on VGAIN sets the
VGA gain to 0 dB, whereas a 1.5 V input sets the VGA gain to
+60 dB if the VGA Gain Mode Polarity Bit CR30, Bit 2, is set
to 0. If the VGA gain mode polarity bit is set to 1, a 0 V input
voltage on VGAIN sets the VGA gain to +60 dB, whereas a 1.5 V
input sets the VGA gain to 0 dB.
The VGA can be powered down by setting Register CR30, Bit 0,
to 0 and can be powered up by setting this same bit to 1.
I2C INTERFACE
The ADRF6850 supports a 2-wire, I2C-compatible serial bus
that drives multiple peripherals. The part powers up in I2C mode
but is not locked in this mode. To remain in I2C mode, it is
ADRF6850
Rev. 0 | Page 21 of 36
recommended that the user tie the CS line to either 3.3 V or
GND, thus disabling SPI mode.
The serial data (SDA) and serial clock (SCL) inputs carry infor-
mation between any devices that are connected to the bus. Each
slave device is recognized by a unique address. The ADRF6850
has two possible 7-bit slave addresses for both read and write
operations, 0x78 and 0x58. The MSB of the 7-bit slave address
is set to 1. Bit 5 of the slave address is set by the CS pin (Pin 27).
Bits[4:0] of the slave address are set to 11000. The slave address
consists of the seven MSBs of an 8-bit word. The LSB of the word
sets either a read or a write operation (see Figure 61). Logic 1 cor-
responds to a read operation, whereas Logic 0 corresponds to a
write operation.
To control the device on the bus, the following protocol must
be followed:
1. The master initiates a data transfer by establishing a start
condition, defined by a high-to-low transition on SDA
while SCL remains high. This indicates that an address/
data stream follows.
2. All peripherals respond to the start condition and shift the
next eight bits (the 7-bit address and the R/W bit). The bits
are transferred from MSB to LSB.
3. The peripheral that recognizes the transmitted address
responds by pulling the data line low during the ninth
clock pulse. This is known as an acknowledge bit.
4. All other devices then withdraw from the bus and maintain
an idle condition. During the idle condition, the device
monitors the SDA and SCL lines waiting for the start
condition and the correct transmitted address.
5. The R/W bit determines the direction of the data. Logic 0
on the LSB of the first byte indicates that the master writes
information to the peripheral. Logic 1 on the LSB of the
first byte indicates that the master reads information from
the peripheral.
The ADRF6850 acts as a standard slave device on the bus. The
data on the SDA pin is eight bits long, supporting the 7-bit
addresses plus the R/W bit. The ADRF6850 has 34 subaddresses
to enable the user-accessible internal registers; therefore, it
interprets the first byte as the device address and the second
byte as the starting subaddress.
Auto-increment mode is supported, which allows data to
be read from or written to the starting subaddress, and each
subsequent address, without manually addressing the subsequent
subaddress. A data transfer is always terminated by a stop con-
dition. The user can also access any unique subaddress register
on a one-by-one basis without updating all registers.
Stop and start conditions can be detected at any stage of the data
transfer. If these conditions are asserted out of sequence with
normal read and write operations, they cause an immediate jump
to the idle condition. If an invalid subaddress is issued by the user,
the ADRF6850 does not issue an acknowledge and returns to the
idle condition. In a no acknowledge condition, the SDA line is
not pulled low on the ninth pulse. See Figure 62 and Figure 63
for sample write and read data transfers, Figure 64 for the timing
protocol, and Figure 2 for a more detailed timing diagram.
1A500000X
MSB = 1 SET BY
PIN 27 0 = W R
1 = RD
SLAVE ADDRESS[6:0] R/W
CTRL
09316-064
Figure 61. Slave Address Configuration
S SLAVE ADDR, L SB = 0 (WR) A(S) A( S ) A(S)DATASUBADDR A(S) PDATA
S = START B IT P = ST OP BIT
A(S) = ACKNO WLEDG E BY SLAVE
09316-067
Figure 62. I2C Write Data Transfer
S
S = START BI T P = STOP BIT
A(S) = ACKNO WLEDG E B Y SL AVE A(M) = ACKNOWLEDGE B Y M AS TER A(M) = NO ACKNOW LEDGE B Y M ASTER
SSLAVE ADDR, LSB = 0 (WR) SLAVE ADDR, LSB = 1 ( RD)A(S) A(S)SUBADDR A(S) DATA A(M) DATA PA(M)
09316-065
Figure 63. I2C Read Data Transfer
START BI T
S
STOP BIT
P
ACKACKWR ACK
D0D7A0A7A5A6
SLAVE
ADDR[4:0]
SLAVE ADDRESS SUBADDRESS DATA
SUBADDR[6:1] DATA[6:1]
SCL
SDA
09316-066
Figure 64. I2C Data Transfer Timing
ADRF6850
Rev. 0 | Page 22 of 36
SPI INTERFACE
The ADRF6850 supports the SPI protocol; however, the part
powers up in I2C mode. To select and lock the SPI mode, three
pulses must be sent to the CS pin, as shown in Figure 65. When
the SPI protocol is locked in, it cannot be unlocked while the
device remains powered up. To reset the serial interface, the
part must be powered down and powered up again.
Serial Interface Selection
The CS pin controls selection of the I2C or SPI interface.
Figure 65 shows the selection process that is required to lock
in the SPI mode. To communicate with the part using the SPI
protocol, three pulses must be sent to the CS pin. On the third
rising edge, the part selects and locks the SPI protocol. Consistent
with most SPI standards, the CS pin must be held low during all
SPI communication to the part and held high at all other times.
SPI Serial Interface Functionality
The SPI serial interface of the ADRF6850 consists of the CS,
SDI (SDI/SDA), CLK (CLK/SCL), and SDO pins. CS is used to
select the device when more than one device is connected to the
serial clock and data lines. CLK is used to clock data in and out
of the part. The SDI line is used to write to the registers. The
SDO pin is a dedicated output for the read mode. The part
operates in slave mode and requires an externally applied serial
clock to the CLK pin. The serial interface is designed to allow
the part to be interfaced to systems that provide a serial clock
that is synchronized to the serial data.
Figure 66 shows an example of a write operation to the ADRF6850.
Data is clocked into the registers on the rising edge of CLK using
a 24-bit write command. The first eight bits represent the write
command (0xD4), the next eight bits are the register address, and
the final eight bits are the data to be written to the specific register.
Figure 67 shows an example of a read operation. In this example,
a shortened 16-bit write command is first used to select the appro-
priate register for a read operation, the first eight bits representing
the write command (0xD4) and the final eight bits representing
the specific register. Then the CS line is pulsed low for a second
time to retrieve data from the selected register using a 16-bit
read command, the first eight bits representing the read command
(0xD5) and the final eight bits representing the contents of the
register being read. Figure 3 shows the timing for both SPI read
and SPI write operations.
09316-077
SPI LOCKED ON
THIRD RISING EDGE SPI FRAMING
EDGE
CBA
SPI LOCKED ON
THIRD RISING EDGE SPI FRAMING
EDGE
CBA
CS
(
STARTIN
G
HIGH)
CS
(
STARTIN
G
LOW)
Figure 65. Selecting the SPI Protocol
ADRF6850
Rev. 0 | Page 23 of 36
REGISTER
ADDRESS
WRITE
COM M AND [ 0xD4]
•••
•••
•••
START
CS
CLK
SDI D7 D6 D5 D4 D3 D2 D1 D0 D0
D7 D6 D5 D4 D3 D2 D1
• • •
• • •
• • •
DATA
BYTE STOP
CS
(CONTINUED)
CLK
(CONTINUED)
SDI
(CONTINUED) D7 D6 D5 D4 D3 D2 D1 D0
09316-068
Figure 66. SPI Byte Write Example
REGISTER
ADDRESS
WRITE
COM M AND [ 0xD4]
START
DATA
BYTE
READ
COM M AND [ 0xD5]
START STOP
CS
CLK
SDI
CS
CLK
SDI
SDO
D7 D6 D5 D4 D3 D2 D1 D0 D0
D7 D6 D5 D4 D3 D2 D1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
X
XXXXXXX
XXXXXXXX
• • •
• • •
• • •
09316-069
Figure 67. SPI Byte Read Example
ADRF6850
Rev. 0 | Page 24 of 36
PROGRAM MODES
The ADRF6850 has 34 8-bit registers to allow program control
of a number of functions. Only 31 of these registers are writeable.
Either an SPI or an I2C interface can be used to program the
register set. For details about the interfaces and timing, see
Figure 61 to Figure 67. The registers are documented in Table 8
to Table 27.
Several settings in the ADRF6850 are double buffered. These
settings include the FRAC value, the INT value, the RFDIV
value, the 5-bit R-divider value, the reference doubler, the R ÷2
divider, and the charge pump current setting. This means that
two events must occur before the part uses a new value for any
of the double buffered settings. First, the new value is latched
into the device by writing to the appropriate register. Next, a new
write must be performed on Register CR0. When Register CR0 is
written, a new PLL acquisition occurs.
For example, updating the fractional value involves a write to
Register CR3, Register CR2, Register CR1, and Register CR0.
Register CR3 should be written to first, followed by Register CR2
and Register CR1 and, finally, Register CR0. The new acquisition
begins after the write to Register CR0. Double buffering ensures
that the bits written to do not take effect until after the write to
Register CR0.
12-Bit Integer Value
Register CR7 and Register CR6 program the integer value (INT)
of the feedback division factor (N); see Equation 5 for details.
The INT value is a 12-bit number whose MSBs are programmed
through Register CR7, Bits[3:0]. The LSBs are programmed
through Register CR6, Bits[7:0]. The LO frequency setting is
described by Equation 2. An alternative to this equation is pro-
vided by Equation 4, which details how to set the N-divider
value. Note that these registers are double buffered.
25-Bit Fractional Value
Register CR3 to Register CR0 program the fractional value (FRAC)
of the feedback division factor (N); see Equation 5 for details. The
FRAC value is a 25-bit number whose MSB is programmed
through Register CR3, Bit 0. The LSB is programmed through
Register CR0, Bit 0. The LO frequency setting is described by
Equation 2. Again, an alternative to this equation is described
by Equation 4, which details how to set the N-divider value.
Note that these registers are double buffered.
RFDIV Value
The RFDIV value is dependent on the value of the LO frequency.
The RFDIV value can be selected from the list in Table 6. Apply
the selected RFDIV value to Equation 4, together with the LO
frequency and PFD frequency values, to calculate the correct N-
divider value.
Reference Input Path
The reference input path consists of a reference doubler, a 5-bit
frequency divider, and a divide-by-2 function (see Figure 54).
The doubler is programmed through Register CR10, Bit 5. The
5-bit divider is enabled by programming Register CR5, Bit 4;
and the division ratio is programmed through Register CR10,
Bits[4:0]. The R ÷2 divider is programmed through Register CR10,
Bit 6. Note that these registers are double buffered.
Charge Pump Current
Register CR9, Bits[7:4], set the charge pump current setting.
With an RSET value of 4.7 kΩ, the maximum charge pump
current is 5 mA. The following equation applies:
ICP max = 23.5/RSET (6)
The charge pump current has 16 settings from 325 μA to 5 mA.
Power-Down/Power-Up Control Bits
The four programmable power-up and power-down control bits
are as follows:
Register CR12, Bit 2. Master power control bit for the PLL,
including the VCO. This bit is normally set to a default
value of 0 to power up the PLL.
Register CR27, Bit 2. Controls the LO monitor outputs,
LOMON and LOMON. The default is 0 when the monitor
outputs are powered down. Setting this bit to 1 powers up
the monitor outputs to one of −6 dBm, −12 dBm, −18 dBm,
or −24 dBm, as controlled by Register CR27, Bits[1:0].
Register CR29, Bit 0. Controls the quadrature demodulator
power. The default is 0, which powers down the demodulator.
Write a 1 to this bit to power up the demodulator.
Register CR30, Bit 0. This bit controls the VGA power and
must be set to a 1 to power up the VGA.
Lock Detect (LDET)
Lock detect is enabled by setting Register CR23, Bit 4, to 1.
Register CR23, Bit 3, in conjunction with Register CR14, Bit 7,
sets the number of up/down pulses generated by the PFD before
lock detect is declared by the LDET pin returning high. The
options are 2048 pulses, 3072 pulses, and 4096 pulses.
The default setting is 3072 pulses, which is selected by program-
ming Register CR23, Bit 3, to 0, and Register CR14, Bit 7, to 0. A
more aggressive setting of 2048 is selected when Register CR23,
Bit 3, is set to 1 and Register CR14, Bit 7, is set to 0. This improves
the lock detect time by 50 μs (for a PFD frequency of 27 MHz).
Note, however, that it does not affect the acquisition time to an
error frequency of 1 kHz. A setting of 4096 pulses is selected
when Register CR14, Bit 7, is set to 1. For best operation, set
Register CR23, Bit 2 to 0. This bit sets up the PFD up/down
pulses to a coarse or low precision setting.
Baseband VOCM Reference
Register CR29, Bit 6, selects whether the common-mode reference
for the baseband outputs is internal or external. When the base-
band outputs are ac-coupled, then the internal reference must
be selected by setting Register CR29, Bit 6, to 1, and by
grounding Pin 7, VOCM.
When the baseband outputs are dc-coupled, it is likely that an
external bias is needed unless the internal dc bias provided is
ADRF6850
Rev. 0 | Page 25 of 36
within a suitable range to match the specification of the follow-
on device. This is accomplished by setting Register CR29, Bit 6,
to 0, and driving Pin 7, VOCM, with the requisite external bias
voltage.
Narrow-Band and Wideband Filter Mode
By default, the second-order low-pass filter in the output buffers
of the baseband output signal paths is selected, and the baseband
outputs are in narrow-band mode. By setting Register CR29,
Bits[5:4], this filter can be set to a cutoff frequency of 50 MHz,
43 MHz, 37 MHz, or 30 MHz. By setting Register CR29, Bit 3, to 1,
this filter is bypassed and wideband mode is selected.
Table 7. Baseband Filter Settings
CR29[5:4] Filter Cutoff Frequency (MHz)
00 50
01 43
10 37
11 30
VGA Gain Mode Polarity
The polarity of the VGA gain is set by programming Bit 2 of
Register CR30. By setting Register CR30, Bit 2, to 0, a positive
gain slope is selected where VGAIN = 0 V sets the VGA gain to be 0
dB, and VGAIN = 1.5 V sets the VGA gain to be 60 dB. By setting
Register CR30, Bit 2, to 1, a negative gain slope is selected.
ADRF6850
Rev. 0 | Page 26 of 36
REGISTER MAP
REGISTER MAP SUMMARY
Table 8. Register Map Summary
Register Address (Hex) Register Name Type Description
0x00 CR0 Read/write Fractional Word 4
0x01 CR1 Read/write Fractional Word 3
0x02 CR2 Read/write Fractional Word 2
0x03 CR3 Read/write Fractional Word 1
0x04 CR4 Read/write Reserved
0x05 CR5 Read/write Reference 5-bit, R-divider enable
0x06 CR6 Read/write Integer Word 2
0x07 CR7 Read/write Integer Word 1
0x08 CR8 Read/write Reserved
0x09 CR9 Read/write Charge pump current setting
0x0A CR10 Read/write Reference frequency control
0x0B CR11 Read/write Reserved
0x0C CR12 Read/write PLL power-up
0x0D CR13 Read/write Reserved
0x0E CR14 Read/write Lock Detector Control 2
0x0F CR15 Read/write Reserved
0x10 CR16 Read/write Reserved
0x11 CR17 Read/write Reserved
0x12 CR18 Read/write Reserved
0x13 CR19 Read/write Reserved
0x14 CR20 Read/write Reserved
0x15 CR21 Read/write Reserved
0x16 CR22 Read/write Reserved
0x17 CR23 Read/write Lock Detector Control 1
0x18 CR24 Read/write Autocalibration
0x19 CR25 Read/write Autocalibration timer
0x1A CR26 Read/write Reserved
0x1B CR27 Read/write LO monitor output
0x1C CR28 Read/write LO selection
0x1D CR29 Read/write Demodulator power and filter selection
0x1E CR30 Read/write VGA
0x1F CR31 Read only Reserved
0x20 CR32 Read only Reserved
0x21 CR33 Read only Revision code
ADRF6850
Rev. 0 | Page 27 of 36
REGISTER BIT DESCRIPTIONS
Table 9. Register CR0 (Address 0x00), Fractional Word 4
Bit Description
7 Fractional Word F71
6 Fractional Word F61
5 Fractional Word F51
4 Fractional Word F41
3 Fractional Word F31
2 Fractional Word F21
1 Fractional Word F11
0 Fractional Word F0 (LSB)1
1 Double buffered. Load on the write to Register CR0.
Table 10. Register CR1 (Address 0x01), Fractional Word 3
Bit Description
7 Fractional Word F151
6 Fractional Word F141
5 Fractional Word F131
4 Fractional Word F121
3 Fractional Word F111
2 Fractional Word F101
1 Fractional Word F91
0 Fractional Word F81
1 Double buffered. Load on the write to Register CR0.
Table 11. Register CR2 (Address 0x02), Fractional Word 2
Bit Description
7 Fractional Word F231
6 Fractional Word F221
5 Fractional Word F211
4 Fractional Word F201
3 Fractional Word F191
2 Fractional Word F181
1 Fractional Word F171
0 Fractional Word F161
1 Double buffered. Load on the write to Register CR0.
Table 12. Register CR3 (Address 0x03), Fractional Word 1
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 Reserved
1 Reserved
0 Fractional Word F24 (MSB)1
1 Double buffered. Load on the write to Register CR0.
Table 13. Register CR5 (Address 0x05), Reference 5-Bit,
R-Divider Enable
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 5-bit R-divider enable1
0 = disable 5-bit R-divider (default)
1 = enable 5-bit R-divider
3 Reserved
2 Reserved
1 Reserved
0 Reserved
1 Double buffered. Load on the write to Register CR0.
Table 14. Register CR6 (Address 0x06), Integer Word 2
Bit Description
7 Integer Word N71
6 Integer Word N61
5 Integer Word N51
4 Integer Word N41
3 Integer Word N31
2 Integer Word N21
1 Integer Word N11
0 Integer Word N01
1 Double buffered. Load on the write to Register CR0.
Table 15. Register CR7 (Address 0x07), Integer Word 1
Bit Description
[7:4] MUXOUT control
0000 = tristate
0001 = logic high
0010 = logic low
1101 = RCLK/2
1110 = NCLK/2
3 Integer Word N111
2 Integer Word N101
1 Integer Word N91
0 Integer Word N81
1 Double buffered. Load on the write to Register CR0.
ADRF6850
Rev. 0 | Page 28 of 36
Table 16. Register CR9 (Address 0x09), Charge Pump
Current Setting
Bit Description
[7:4] Charge pump current1
0000 = 0.31 mA (default)
0001 = 0.63 mA
0010 = 0.94 mA
0011 = 1.25 mA
0100 = 1.57 mA
0101 = 1.88 mA
0110 = 2.19 mA
0111 = 2.50 mA
1000 = 2.81 mA
1001 = 3.13 mA
1010 = 3.44 mA
1011 = 3.75 mA
1100 = 4.06 mA
1101 = 4.38 mA
1110 = 4.69 mA
1111 = 5.00 mA
3 Reserved
2 Reserved
1 Reserved
0 Reserved
1 Double buffered. Load on the write to Register CR0.
Table 17. Register CR10 (Address 0x0A), Reference
Frequency Control
Bit Description
7 Reserved1
6 R divide-by-2 divider enable1
0 = bypass R divide-by-2 divider
1 = enable R divide-by-2 divider
5 R-doubler enable1
0 = disable doubler (default)
1 = enable doubler
[4:0] 5-bit R-divider setting1
00000 = divide by 32 (default)
00001 = divide by 1
00010 = divide by 2
…
11110 = divide by 30
11111 = divide by 31
1 Double buffered. Load on the write to Register CR0.
Table 18. Register CR12 (Address 0x0C), PLL Power-Up
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 PLL power-down
0 = power up PLL (default)
1 = power down PLL
1 Reserved
0 Reserved
Table 19. Register CR14 (Address 0x0E), Lock Detector
Control 2
Bit Description
7 Lock Detector Up/Down Count 2
0 = 2048/3072 up/down pulses
1 = 4096 up/down pulses
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 Reserved
1 Reserved
0 Reserved
Table 20. Register CR23 (Address 0x17), Lock Detector
Control 1
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Lock detector enable
0 = lock detector disabled (default)
1 = lock detector enabled
3 Lock detector up/down count
With Register CR14[7] = 0:
0 = 3072 up/down pulses
1 = 2048 up/down pulses
2 Lock detector precision
0 = low, coarse (16 ns)
1 = high, fine (6 ns)
1 Reserved
0 Reserved
ADRF6850
Rev. 0 | Page 29 of 36
Table 21. Register CR24 (Address 0x18), Autocalibration
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 Reserved
1 Reserved
0 Disable autocalibration
0 = enable autocalibration (default)
1 = disable autocalibration
Table 22. Register CR25 (Address 0x19), Autocalibration
Timer
Bit Description
[7:0] Autocalibration timer
Table 23. Register CR27 (Address 0x1B), LO Monitor Output
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 Power-up monitor output
0 = power down (default)
1 = power up
[1:0] Monitor output power into 50 Ω
00 = −24 dBm (default)
01 = −18 dBm
10 = −12 dBm
11 = −6 dBm
Table 24. Register CR28 (Address 0x1C), LO Selection
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved; set to 1
[2:0] RFDIV
000 = divide by 1; LO = 500 MHz to 1000 MHz
001 = divide by 2; LO = 250 MHz to 500 MHz
010 = divide by 4; LO = 125 MHz to 250 MHz
011 = divide by 8; LO = 100 MHz to 125 MHz
Table 25. Register CR29 (Address 0x1D), Demodulator
Power and Filter Selection
Bit Description
7 Reserved
6 Internal baseband (V
OCM
) select
0 = select external baseband (VOCM) reference
1 = select internal baseband (VOCM) reference
[5:4] Narrow-band filter cut off
00 = 50 MHz
01 = 43 MHz
10 = 37 MHz
11 = 30 MHz
3 Baseband wideband/narrow-band modes
0 = narrow-band mode
1 = wideband mode
2 Reserved; set to 0
1 Reserved; set to 0
0 Power-up demodulator
0 = power down (default)
1 = power up
Table 26. Register CR30 (Address 0x1E), VGA
Bit Description
7 Reserved
6 Reserved
5 Reserved
4 Reserved
3 Reserved
2 VGA gain mode polarity
0 = positive gain slope
1 = negative gain slope
1 Reserved
0 Power-up VGA
0 = power down
1 = power up
Table 27. Register CR33 (Address 0x21), Revision Code1
Bit Description
7 Revision code
6 Revision code
5 Revision code
4 Revision code
3 Revision code
2 Revision code
1 Revision code
0 Revision code
1 Read-only register.
ADRF6850
Rev. 0 | Page 30 of 36
SUGGESTED POWER-UP SEQUENCE
INITIAL REGISTER WRITE SEQUENCE
After applying power to the device, adhere to the following
write sequence, particularly with respect to the reserved register
settings. Note that Register CR33, Register CR32, and
Register CR31 are read-only registers. Also note that all
writeable registers should be written to on power-up. Refer to
the Register Map section for more details on all registers.
1. Write the following to Register CR30 = 0x00. Set VGA
power to off and the VGA gain slope to be positive.
2. Write the following to Register CR29: 0x41. The
demodulator is powered up. The baseband narrow-band
mode is selected and set to a cutoff frequency of 50 MHz.
The internal baseband VOCM reference is selected.
3. Write the following to Register CR28: 0x0X RFDIV
depends on the value of the LO frequency to be used and is
set according to Table 6. Note that Register CR28, Bit 3, is
set to 1.
4. Write the following to Register CR27: 0x00. Power the LO
monitor in a power-down state.
5. Write the following to Register CR26: 0x00. Reserved
register.
6. Write the following to Register CR25: 0x70. Set the
autocalibration time to 100 μs with a PFD frequency
setting of 27 MHz. If the PFD frequency is different, set
CR25 according to Equation 3.
7. Write the following to Register CR24: 0x38. Enable
autocalibration.
8. Write the following to Register CR23: 0x70. Enable lock
detector and set lock detector counter = 3072 up/down
pulses.
9. Write the following to Register CR22: 0x00. Reserved
register.
10. Write the following to Register CR21: 0x00. Reserved
register.
11. Write the following to Register CR20: 0x00. Reserved
register.
12. Write the following to Register CR19: 0x00. Reserved
register.
13. Write the following to Register CR18: 0x60. Reserved
register.
14. Write the following to Register CR17: 0x00. Reserved
register.
15. Write the following to Register CR16: 0x00. Reserved
register.
16. Write the following to Register CR15: 0x00. Reserved
register.
17. Write Register CR14: 0x00. Lock Detector Control 2.
18. Write Register CR13: 0x08. Reserved register.
19. Write the following to Register CR12: 0x18. PLL powered up.
20. Write the following to Register CR11: 0x00. Reserved
register.
21. Write the following to Register CR10: 0x21. The reference
path doubler is enabled and the 5-bit divider and R divide-
by-2 divider are bypassed.
22. Write the following to Register CR9: 0x70. With the
recommended loop filter component values and RSET =
4.7 kΩ, the charge pump current is set to 2.5 mA for a loop
bandwidth of 50 kHz.
23. Write the following to Register CR8: 0x00. Reserved
register.
24. Write the following to Register CR7: 0x0X. Set according to
Equation 4 and Equation 5 in the Theory of Operation
section.
25. Write the following to Register CR6: 0xXX. Set according
to Equation 4 and Equation 5 in the Theory of Operation
section.
26. Write Register CR5: 0x00. Disable the 5-bit reference
divider.
27. Write the following to Register CR4: 0x01. Reserved
register.
28. Write the following to Register CR3: 0x0X. Set according to
Equation 4 and Equation 5 in the Theory of Operation
section.
29. Write the following to Register CR2: 0xXX. Set according
to Equation 4 and Equation 5 in the Theory of Operation
section.
30. Write the following to Register CR1: 0xXX. Set according
to Equation 4 and Equation 5 in the Theory of Operation
section.
31. Write the following to Register CR0: 0xXX. Set according
to Equation 4 and Equation 5 in the Theory of Operation
section. Register CR0 must be the last register written for
all the double buffered bit writes to take effect.
32. Monitor the LDET output or wait 260 μs to ensure that the
PLL is locked.
33. Write the following to Register CR30: 0x01. Set the VGA to
power on.
ADRF6850
Rev. 0 | Page 31 of 36
EVALUATION BOARD
GENERAL DESCRIPTION
The evaluation board is designed to allow the user to evaluate
the performance of the ADRF6850. It contains the following:
• The ADRF6850 DUT. This is an I/Q demodulator with an
integrated fractional-N PLL and VCO.
• SPI and I2C interface connectors.
• Baseband output connectors.
• Fourth-order low-pass loop filter circuitry.
• 13.5 MHz reference clock, and the ability to drive the
reference input external to the board.
• Circuitry to support differential signaling to the TESTLO
inputs, including dc biasing circuitry.
• Circuitry to monitor the LOMON outputs.
• SMA connectors for power supplies, the VGAIN input and
a single-ended RF input.
The evaluation board comes with associated software to allow
easy programming of the ADRF6850.
HARDWARE DESCRIPTION
For more information, refer to the circuit diagram in Figure 69.
Power Supplies
An external +3.3 V supply (DUT + 3.3 V) powers each of the
nine VCCx supplies on the ADRF6850 as well as the 13.5 MHz
clock reference.
Recommended Decoupling for Supplies
Initially, the external +3.3 V supply is decoupled by a 10 µF
capacitor and then further by a parallel combination of 100 nF
and 56 pF capacitors that are placed as close to the DUT as
possible for good local decoupling. The impedance of all these
capacitors should be low and constant across a broad frequency
range. Surface-mount multilayered ceramic chip (MLCC) Class II
capacitors provide very low ESL and ESR, which assist in
decoupling supply noise effectively. They also provide good
temperature stability and good aging characteristics. Capacitance
changes per the bias voltage that is applied. Larger case sizes have
less capacitance change vs. applied bias voltage, and also lower
ESR but higher ESL. A combination of 0402 size cases for the
56 pF capacitors and 0603 size cases for the 100 nF capacitors
give a good compromise allowing the 56 pF capacitors to be
placed as close as possible to the supply pins on the top side of
the PCB with the 100 nF capacitors placed on the bottom side
of the PCB quite close to the supply pins. X5R and X7R
capacitors are examples of these types of capacitors and are
recommended for decoupling.
SPI and I2C Interface
The SPI interface connector is a nine-way, D-type connector that
can be connected to the printer port of a PC. Figure 68 shows
the PC cable diagram that must be used with the provided
software.
There is also an option to use the I2C interface by using the I2C
receptacle connector. This is a standard I2C connector. A supply
voltage of +3.3 V is provided by the I2C bus master. Pull-up
resistors are required on the signal lines. The CS pin can be
used to set the slave address of the ADRF6850. CS high sets the
slave address to 0x78, and CS low sets the slave address to 0x58.
6
7
8
9
1
9-WAY
FEMALE
D-TYPE
25-WAY
MALE
D-TYPE
TO PC
PRI NTER PORT
GND
CLK
DATA
LE
2
3
4
5
21
22
23
24
25
8
9
10
11
12
4
5
6
7
1
2
3
16
17
18
19
20
14
15
13
PC
09316-070
Figure 68. SPI PC Cable Diagram
ADRF6850
Rev. 0 | Page 32 of 36
Baseband Outputs and VOCM
The pair of I and Q baseband outputs are connected to the
board by SMA connectors. They are ac-coupled to the output
connectors. VOCM, which sets the common-mode output
voltage, is grounded and the internal baseband (VOCM) reference
is selected by Register CR29, Bit 6. If the external baseband
(VOCM) reference is selected by setting this bit to a 0, then a
voltage needs to be applied through J6 and R20 needs to be
removed.
Loop Filter
A fourth-order loop filter is provided at the output of the charge
pump and is required to adequately filter noise from the Σ-Δ
modulator used in the N-divider. With the charge pump current
set to a midscale value of 2.5 mA and using the on-chip VCO,
the loop bandwidth is approximately 50 kHz, and the phase
margin is 55°. C0G capacitors are recommended for use in the
loop filter because they have low dielectric absorption, which is
required for fast and accurate settling time. The use of non C0G
capacitors may result in a long tail being introduced into the
PLL settling time transient.
Reference Input
The reference input can be supplied by a 13.5 MHz Jauch clock
generator or by an external clock through the use of Connector J7.
The frequency range of the reference input is from 10 MHz to
300 MHz with the PFD frequency limited to a maximum of
30 MHz. Double the 13.5 MHz clock to 27 MHz by using the on-
chip reference frequency doubler to optimize phase noise
performance.
TESTLO Inputs
These pins are differential test inputs that allow a variety of debug
options. On this board, the capability is provided to drive these
pins with an external 4× LO signal that is then applied to an
Anaren balun to provide a differential input signal.
When driving the TESTLO pins, the PLL can be bypassed, and
the demodulator can be driven directly by this external LO
signal. The frequency of the LO signal needs to be 4 times the
operating frequency. These inputs also require a dc bias. A dc
bias of 3.3 V is the default option used on the board.
LOMON Outputs
These pins are differential LO monitor outputs that provide a
replica of the internal LO frequency at 1× LO. The single-ended
power in a 50 Ω load can be programmed to −24 dBm, −18 dBm,
−12 dBm, or −6 dBm. These open-collector outputs must be
terminated to 3.3 V. Because both outputs must be terminated
to 50 Ω, options are provided to terminate to 3.3 V using on-
board 50 Ω resistors or by series inductors (or a ferrite bead), in
which case the 50 Ω termination is provided by the measuring
instrument.
CCOMPx Pins
The CCOMPx pins are internal compensation nodes that must
be decoupled to ground with a 100 nF capacitor.
MUXOUT
MUXOUT is a test output that allows different internal nodes
to be monitored. It is a CMOS output stage that requires no
termination.
Lock Detect (LDET)
Lock detect is a CMOS output that indicates the state of the
PLL. A high level indicates a locked condition, and a low level
indicates a loss of lock condition.
RF Inputs (RFI, RFCM, and RFI)
RFI and RFI are 50 Ω internally biased RF inputs. For single-
ended operation as demonstrated on the evaluation board, RFI
must be ac-coupled to the source and RFI must be ac-coupled
to the ground plane. RFCM is the RF input common-mode pin.
It should be connected to RFI when driving the input in single-
ended mode. When driving the input differentially using a
balun, connect this pin to the common terminal of the output
coil of the balun.
VGAIN
The VGAIN pin sets the gain of the VGA. The VGAIN voltage
range is from 0 V to 1.5 V. This allows the gain of the VGA to
vary from 0 dB to +60 dB.
ADRF6850
Rev. 0 | Page 33 of 36
PCB SCHEMATIC
09316-058
Figure 69. Applications Circuit
ADRF6850
Rev. 0 | Page 34 of 36
PCB ARTWORK
Component Placement
09316-071
Figure 70. Evaluation Board, Top Side Component
09316-073
Figure 71. Evaluation Board, Top Side—Layer 1
09316-075
Figure 72. Evaluation Board, Ground—Layer 2
09316-072
Figure 73. Evaluation Board, Bottom Side Component Placement
09316-076
Figure 74. Evaluation Board Power—Layer 3
09316-074
Figure 75. Evaluation Board, Bottom Side—Layer 4
ADRF6850
Rev. 0 | Page 35 of 36
BILL OF MATERIALS
Table 28. Bill of Materials
Qty. Reference Designator Description Manufacturer Part Number
1 DUT ADRF6850 LFCSP, 56-lead 8 mm × 8 mm Analog Devices ADRF6850BCPZ
1 Y2 VCO, 13.5 MHz Jauch 0 13.50-VX7-G-3.3-1-
T1-LF
1 SPI Connector, 9-pin, D-sub plug, D-SUB9MR ITW McMurdo FEC 1071806
1 I2C Connector, I2C, SEMCONN receptacle Digikey 5-1761185-1-ND
2 C1, C34 Capacitor, 10 µF, 25 V, tantalum, TAJ-C AVX FEC 197518
10 C4, C6, C10, C12, C14, C16, C40,
C48, C53, C55
Capacitor, 56 pF, 50 V, ceramic, C0G, 0402 AVX FEC 1658861
14 C5, C7, C11, C13, C15, C17, C22,
C27, C47, C49 to C52, C54
Capacitor, 100 nF, 25 V, X7R, ceramic, 0603 AVX FEC 317287
1 C3 Capacitor, 1.8 nF, 50 V, C0G, ceramic, 0603 Murata FEC 1402814
1 C35 Capacitor, 68 nF, 50 V, NPO, ceramic, 1206 Kemet FEC 1535582
4 C2, C21, C38, C39 Capacitor, 1 nF, 50 V, C0G, ceramic, 0603 Murata FEC 8819920
2 C44, C46 Capacitor, 100 pF, 50 V, C0G, ceramic, 0402 Murata FEC 8819572
2 C43, C56 Capacitor, 10 nF, 50 V, X7R, ceramic, 0402 Murata FEC 1414575
1 C18 Capacitor, 10 pF, 50 V, C0G, ceramic, 0402 Murata FEC 8819564
4 C30 to C33 Capacitor, 10 μF, 6.3 V, X5R, ceramic, 0603 Phycomp FEC 1458902
12 J2 to J12, J14 SMA end launch connector Johnson/Emerson 142-0701-851
2 J20, J21 Jumper, 3-pin plus shunt Harwin FEC 148533 +
FEC 150411
2 L1, L2 Inductor, 20 nH, 0402, LQW series Murata LQW15AN20N
2 L3, L4 Inductor, 10 µH, 0805, LQM series Murata LQM21FN1N100M
2 R20, R36 Resistor, 0 Ω, 1/16 W, 1%, 0402 Vishay Draloric FEC 1158241
1 R13 Resistor, 4.7 kΩ, 1/10 W, 1%, 0603 Multicomp FEC 1576293
2 R14, R39 Resistor, 1.2 kΩ, 1/10 W, 5%, 0603 Phycomp FEC 9233393
1 R1 Resistor, 220 Ω, 1/16 W, 1%, 0603 Multicomp FEC 9330801
2 R3, R4 Resistor, 200 Ω, 1/16 W, 5%, 0402 Vishay Dale FEC 1514682
2 R17, R18 Resistor, 0603, spacing (do not install)
3 R35, R44, R45 Resistor, 51 Ω, 1/16 W, 1%, 0402 Multicomp FEC 1358008
4 R48 to R51 Resistor, 330 Ω, 1/10 W, 5%, 0805 Vishay Draloric FEC 1739223
2 R60, R61 Resistor, 100 Ω, 1/10 W, 5%, 0805 Bourns Digi Key
RR12P100DTR-ND
2 R46, R47 Resistor, 10 kΩ, 1/16 W, 1%, 0402 Phycomp FEC 9239359
7 CS, LDET, MUXOUT, VTUNE, SCLK,
SDA, SDO
Test point, 1-pin, 0.035 inch diameter Not inserted
1 BAL1 Balun, 0805, 50 Ω to 100 Ω balanced (1.3 GHz to
3.1 GHz)
Anaren BD1631J50100A00
ADRF6850
Rev. 0 | Page 36 of 36
OUTLINE DIMENSIONS
COMPLIANT TO JEDEC STANDARDS MO-220-VLLD-2
081809-B
TOPVIEW
1
56
14
15
43
42
28
29
5.25
5.10 SQ
4.95
0.50
0.40
0.30
0.30
0.23
0.18
0.20 REF
12° MAX 0.8
0 MAX
0.65 TYP
1.00
0.85
0.80
6.50 REF
SEATING
PLANE
0.60 MAX
0.60
MAX
COPLANARITY
0.08
0.05 MAX
0.02 NOM
0.25 MIN
FOR PROPER CONNECTION OF
THE EXPOSED PAD, REFER TO
THE PIN CONFIGURATION AND
FUNCTION DESCRIPTIONS
SECTION OF THIS DATA SHEET.
PIN 1
INDICATOR
8.10
8.00 SQ
7.90
7.85
7.75 SQ
7.65
0.50
BSC
BOTTOMVIEW
EXPOSED
PAD
PIN 1
INDICATOR
Figure 76. 56-Lead Lead Frame Chip Scale Package [LFCSP_VQ]
8 mm × 8 mm Body, Very Thin Quad
(CP-56-5)
Dimensions shown in millimeters
ORDERING GUIDE
Model1Temperature Range Package Description Package Option
ADRF6850BCPZ −40°C to +85°C 56-Lead Lead Frame Chip Scale Package [LFCSP_VQ], Tray CP-56-5
ADRF6850BCPZ-R7 −40°C to +85°C 56-Lead Lead Frame Chip Scale Package [LFCSP_VQ], 7" Tape and Reel CP-56-5
EVAL-ADRF6850EB1Z Evaluation Board
1 Z = RoHS Compliant Part.
I2C refers to a communications protocol originally developed by Philips Semiconductors (now NXP Semiconductors).
©2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
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