EVALUATION KIT AVAILABLE
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer/VCO
General Description
Benefits and Features
The MAX2871 is an ultra-wideband phase-locked loop (PLL)
with integrated voltage control oscillators (VCOs) capable
of operating in both integer-N and fractional-N modes.
When combined with an external reference oscillator and
loop filter, the MAX2871 is a high-performance frequency
synthesizer capable of synthesizing frequencies from
23.5MHz to 6.0GHz while maintaining superior phase
noise and spurious performance.
The ultra-wide frequency range is achieved with the
help of multiple integrated VCOs covering 3000MHz to
6000MHz, and output dividers ranging from 1 to 128. The
device also provides dual differential output drivers, which
can be independently programmed to deliver -1dBm to
+8dBm differential output power. Both outputs can be
muted by either software or hardware control.
The MAX2871 is controlled by a 4-wire serial interface and
is compatible with 1.8V control logic. The device is available
in a lead-free, RoHS-compliant, 5mm x 5mm, 32-pin TQFN
package, and operates over an extended -40°C to +85°C
temperature range.
The MAX2871 has an improved feature set and better overall
phase noise and is fully pin and software-compatible with the
MAX2870.
Applications
● Wireless Infrastructure
● Test and Measurement
● Output Binary Buffers/Dividers Enable Extended
Frequency Range
• Divider Ratios of 1/2/4/8/16/32/64/128
• 23.5MHz to 6000MHz
● High-Performance Phase Frequency Detector (PFD)
and Reference Frequency Reduces Spectral Noise
• PFD Up to 140MHz
• Reference Frequency Up to 210MHz
● Low Normalized Inband Phase Noise of -230dBc/Hz
Reduces System Noise Floor Contribution
● Manual/Automatic VCO Selection Permits Fast
Switching
● Output Phase Reset and Adjustment Allow
Synchronization of Multiple Synthesizers
● On-Chip Temperature Sensor with 7-Bit ADC Ensures
Optimum VCO Selection
● Cycle Slip Reduction and Fast Lock Features
Improve Accuracy and Acquisition Time
● VCO Lock Maintained Over Entire Temperature
Range Provides Glitch-Free Operation
● Dual Differential Programmable Outputs Maximize
Flexibility of Use
● Clock Generation
● Microwave Radios
Ordering Information and “Typical Application Circuit”
appears at end of data sheet.
Functional Diagram
MUX
MUX
MAX2871
LD
LOCK DETECT
REF_IN
X2
MUX
R COUNTER
MUX
DIVIDE-BY-2
CHARGE
PUMP
CP_OUT
GND_CP
CLK
TUNE
SPI AND
REGISTERS
DATA
LE
VCO
INTEGER
FRAC
MODULUS
DIV-BY1/2/4/8/16
RFOUTA_P
DIV-BY1/2/4/8
RFOUTA_N
RFOUT_EN
MAIN
MODULATOR
RFOUTB_P
MUX
N COUNTER
MUX
19-7106; Rev 4; 6/20
RFOUTB_N
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Absolute Maximum Ratings
VCC_ to GND_.......................................................-0.3V to +3.9V
All Other Pins to GND_..............................-0.3V to VCC_ + 0.3V
Continuous Power Dissipation (TA = +70°C)
TQFN-EP Multilayer Board
(derate 34.5mW/°C above +70°C)..........................2758.6mW
Junction Temperature.......................................................+150°C
Operating Temperature Range............................ -40°C to +85°C
Storage Temperature Range............................. -65°C to +150°C
Lead Temperature (soldering, 10s)................................. +300°C
Soldering Temperature (reflow)........................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Package Thermal Characteristics (Note 1)
TQFN
Junction-to-Ambient Thermal Resistance (θJA)...........29°C/W
Junction-to-Case Thermal Resistance (θJC)...............1.7°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
DC Electrical Characteristics
(Measured using MAX2871 EV Kit. VCC_ = 3V to 3.6V, VGND_ = 0V, fREF_IN = 50MHz, fPFD = 50MHz, TA = -40°C to +85°C. Typical
values measured at VCC_ = 3.3V; TA = +25°C; register settings (Reg 0:5) 00780000, 20000141, 01005E42, 00000013, 610F423C,
01400005;. unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
Supply Voltage
RFOUT_ Current Consumption
Supply Current
MIN
TYP
MAX
UNITS
3
3.3
3.6
V
IRFOUT_, minimum output power, single channel
9
IRFOUT_, maximum output power, single channel
25
Total, including RFOUT, both
channel (Note 3)
165
Both channels
enabled,
maximum output
power
Each output divide-by-2
mA
200
8
ICCVCO + ICCRF (Note 3)
mA
122
Low-power sleep mode
1
AC Electrical Characteristics
(Measured using MAX2871 EV Kit. VCC_ = 3V to 3.6V, VGND_ = 0V, fREF_IN = 50MHz, fPFD = 25MHz, fRFOUT_ = 6000MHz,
TA = -40°C to +85°C. Typical values measured at VCC_ = 3.3V, TA = +25°C, register settings (Reg 0:5) 00780000, 20000141,
01005E42, 00000013, 610F423C, 01400005; unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
REFERENCE OSCILLATOR INPUT (REF_IN)
REF_IN Input Frequency Range
10
210
MHz
REF_IN Input Sensitivity
0.7
VCC_
VP-P
REF_IN Input Capacitance
2
REF_IN Input Current
-60
pF
+60
µA
PHASE DETECTOR
Phase Detector Frequency
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Integer-N mode
140
Fractional-N mode
125
MHz
Maxim Integrated │ 2
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
AC Electrical Characteristics (continued)
(Measured using MAX2871 EV Kit. VCC_ = 3V to 3.6V, VGND_ = 0V, fREF_IN = 50MHz, fPFD = 25MHz, fRFOUT_ = 6000MHz,
TA = -40°C to +85°C. Typical values measured at VCC_ = 3.3V, TA = +25°C, register settings (Reg 0:5) 00780000, 20000141,
01005E42, 00000013, 610F423C, 01400005; unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE PUMP
Sink/Source Current
CP[3:0] = 1111, RSET = 5.1kΩ
5.12
CP[3:0] = 0000, RSET = 5.1kΩ
0.32
RSET Range
mA
2.7
10
kΩ
3000
6000
MHz
RF OUTPUTS
Fundamental Frequency Range
Divided Frequency Range
With output dividers (1/2/4/8/16/32/64/128)
VCO Sensitivity
23.4375
6000
MHz
100
MHz/V
Frequency Pushing
Open loop
0.8
MHz/V
Frequency Pulling
Open loop into 2:1 VSWR
70
kHz
2nd Harmonic
Fundamental VCO output
-40
dBc
3rd Harmonic
Fundamental VCO output
-34
dBc
2nd Harmonic
VCO output divided-by-2
-25
dBc
3rd Harmonic
VCO output divided-by-2
-20
dBc
Maximum Output Power
fRFOUT_ = 3000MHz (Note 4)
5
dBm
Minimum Output Power
fRFOUT_ = 3000MHz (Note 4)
-4
dBm
-40°C ≤ TA ≤ +85°C
1
Output Power Variation (Note 4)
Muted Output Power
3V ≤ VCC_ ≤ 3.6V
0.2
(Note 4)
-40
dB
dBm
VCO AND FREQUENCY SYNTHESIZER NOISE
VCO at 3000MHz
VCO Phase Noise (Note 5)
VCO at 4500MHz
VCO at 6000MHz
10kHz offset
-83
100kHz offset
-111
1MHz offset
-136
5MHz offset
-149
10kHz offset
-77
100kHz offset
-106
1MHz offset
-132
5MHz offset
-147
10kHz offset
-71
100kHz offset
-101
1MHz offset
-128
5MHz offset
-144
dBc/Hz
In-Band Noise Floor
Normalized (Note 6)
-230
dBc/Hz
1/f Noise
Normalized (Note 7)
-122
dBc/Hz
In-Band Phase Noise
(Note 8)
-102
dBc/Hz
Integrated RMS Jitter
(Note 9)
0.2
ps
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Maxim Integrated │ 3
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
AC Electrical Characteristics (continued)
(Measured using MAX2871 EV Kit. VCC_ = 3V to 3.6V, VGND_ = 0V, fREF_IN = 50MHz, fPFD = 25MHz, fRFOUT_ = 6000MHz,
TA = -40°C to +85°C. Typical values measured at VCC_ = 3.3V, TA = +25°C, register settings (Reg 0:5) 00780000, 20000141,
01005E42, 00000013, 610F423C, 01400005; unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
Spurious Signals Due to PFD Frequency
MIN
MAX
-88
50kHz loop bandwidth
VCO Tune Voltage
TYP
dBc
VCC_
- 0.5
0.5
UNITS
V
TEMPERATURE SENSOR AND ADC
ADC Resolution
7
Bits
Temperature Sensor Accuracy
3
°C
DIGITAL I/O CHARACTERISTICS
(VCC_ = +3V to +3.6V, VGND_ = 0V, TA = -40°C to +85°C. Typical values at VCC_ = 3.3V, TA = +25°C.) (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SERIAL INTERFACE INPUTS (CLK, DATA, LE, CE, RFOUT_EN)
Input Logic-Level Low
VIL
0.4
V
Input Logic-Level High
VIH
1.5
V
Input Current
IIH/IIL
-1
Input Capacitance
+1
1
µA
pF
SERIAL INTERFACE OUTPUTS (MUX, LD)
Output Logic-Level Low
Output Logic-Level High
Output Current Level High
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0.3mA sink current
0.3mA source current
0.4
VCC 0.4
V
V
0.5
mA
Maxim Integrated │ 4
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
SPI TIMING CHARACTERISTICS
(VCC_ = +3V to +3.6V, VGND_ = 0V, TA = -40°C to +85°C. Typical values at VCC_= 3.3V, TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
CLK Clock Period
tCP
CLK Pulse-Width Low
CONDITIONS
Guaranteed by CLK pulse-width
low and high
MIN
TYP
MAX
UNITS
50
ns
tCL
25
ns
CLK Pulse-Width High
tCH
25
ns
LE Setup Time
tLES
20
ns
LE Hold Time
tLEH
10
ns
LE Minimum Pulse-Width High
tLEW
20
ns
DATA Setup Time
tDS
25
ns
DATA Hold Time
tDH
25
ns
MUX Valid
tDOT
MUX transition valid after CLK rise
10
ns
Note 2: Production tested at TA = +25°C. Cold and hot are guaranteed by design and characterization.
Note 3: fREF_IN = 100MHz, phase detector frequency = 25MHz, RF output = 6000MHz.
Register setting: 00780000, 00400061, 34011242, F8010003, 638FF1FC, 80400005.
Note 4: Measured single ended with 27nH to VCC_RF into 50Ω load. Power measured with single output enabled. Unused output
has 27nH to VCC_RF with 50Ω termination.
Note 5: VCO phase noise is measured open loop.
Note 6: Measured at 200kHz using a 50MHz Bliley NV108C19554 OCVCXO with 2MHz loop bandwidth. Register setting
801E0000, 8000FFF9, 80005FC2, 6C10000B, 638E80FC, 400005. EV kit loop filter: C2 = 1500pF, C1 = 33pF, R2A = 0Ω,
R2B = 1100Ω, R3 = 0Ω, C3 = open.
Note 7: 1/f noise contribution to the in-band phase noise is computed by using 1/f noise + 10log(10kHz/fOFFSET) +
20log(fRF/1GHz). Register setting: 803A0000, 8000FFF9, 81005F42, F4000013, 6384803C, 001500005.
Note 8: fREF_IN = 50MHz; fPFD = 25MHz; offset frequency = 10kHz; VCO frequency = 4227MHz, output divide-by-2 enabled.
RFOUT = 2113.5MHz; N = 169; loop BW = 40kHz, CP[3:0] = 1111; integer mode.
Note 9: fREF_IN = 50MHz; fPFD = 50MHz; VCO frequency = 4400MHz, fRFOUT_ = 4400MHz; loop BW = 65kHz. Register setting:
002C0000, 200303E9, 80005642, 00000133, 638E82FC, 01400005. EV kit loop filter: C2 = 0.1µF, C1 = 0.012µF,
R2A = 0Ω, R2B = 120Ω, R3 = 250Ω, C3 = 820pF.
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Maxim Integrated │ 5
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Operating Characteristics
(Measured with MAX2871 EV Kit. VCC_ = 3.3V, VGND_ = 0V, fREF_IN = 50MHz, TA = +25°C, see the Typical Operating Characteristics
Testing Conditions Table Table.)
3.0GHz VCO OPEN-LOOP PHASE NOISE
vs. FREQUENCY
toc01
-40
-50
-60
-60
-60
-70
-70
-70
-100
-110
-120
-130
-140
-150
-160
-80
-90
-100
-110
-120
-130
10k
100k
1M
10M
100M
1k
10k
-90
DIV4
-80
DIV2
DIV16
-110
DIV32
DIV64
-120
DIV128
-130
-140
10M
-130
-160
100M
DIV2
DIV4
DIV8
-100
DIV16
-110
DIV32
DIV64
-120
DIV128
-130
-140
DIV4
10M
-40
-60
-80
toc08
-80
-120
-140
-140
-160
-160
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10M
100M
10M
100M
toc09
-70
-90
-60
-120
1M
-80
-100
-100
100k
2113.5MHz FRACTIONAL-N PHASE NOISE
vs. FREQUENCY (LOW-NOISE MODE)
PHASE NOISE (dBc/Hz)
-40
PHASE NOISE (dBc/Hz)
SPURS (dBc)
-20
100k
1M
FREQUENCY (Hz)
10k
FREQUENCY (Hz)
0
-20
10k
1k
2687.5MHz INTEGER-N MODE PHASE NOISE
AND SPUR PERFORMANCE vs. FREQUENCY
toc07
0
1k
-170
100M
DIV64
DIV128
FREQUENCY (Hz)
904MHz INTEGER-N MODE PHASE NOISE
AND SPUR PERFORMANCE vs. FREQUENCY
PHASE NOISE (dBc/Hz)
SPURS (dBc)
1M
DIV32
-140
-160
100k
DIV16
-130
-170
10k
DIV8
-120
-170
1k
DIV2
-110
-150
100M
100M
6.0GHZ CLOSED-LOOP PHASE NOISE
vs. FREQUENCY
toc06
-100
-160
10M
10M
-90
-160
100k
1M
FREQUENCY (Hz)
100k
1M
FREQUENCY (Hz)
DIV1
-150
10k
10k
-80
-150
1k
1k
-70
DIV1
-90
DIV8
-100
100k
1M
FREQUENCY (Hz)
4.5GHZ CLOSED-LOOP PHASE NOISE
vs. FREQUENCY
toc05
-70
PHASE NOISE (dBc/Hz)
PHASE NOISE (dBc/Hz)
DIV1
-120
-150
3.0GHZ CLOSED-LOOP PHASE NOISE
vs. FREQUENCY
toc04
-80
-110
-140
FREQUENCY (Hz)
-70
-90
-100
-150
-160
1k
-80
-140
PHASE NOISE (dBc/Hz)
-90
PHASE NOISE (dBc/Hz)
-50
-80
6.0GHz VCO OPEN-LOOP PHASE NOISE
vs. FREQUENCY
toc03
-40
-50
PHASE NOISE (dBc/Hz)
PHASE NOISE (dBc/Hz)
-40
4.5GHz VCO OPEN-LOOP PHASE NOISE
vs. FREQUENCY
toc02
-100
-110
-120
-130
-140
-150
-160
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
-170
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
Maxim Integrated │ 6
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Operating Characteristics (continued)
(Measured with MAX2871 EV Kit. VCC_ = 3.3V, VGND_ = 0V, fREF_IN = 50MHz, TA = +25°C, see the Typical Operating Characteristics
Testing Conditions Table Table.)
2113.5MHz FRACTIONAL-N PHASE NOISE
vs. FREQUENCY (LOW-SPUR MODE)
2679.4MHz FRACTIONAL-N PHASE NOISE
vs. FREQUENCY (LOW-NOISE MODE)
toc10
toc11
-70
-80
-90
-90
-90
-100
-100
-100
-120
-130
-140
-80
PHASE NOISE (dBc/Hz)
-110
-110
-120
-130
-140
-110
-120
-130
-140
-150
-150
-150
-160
-160
-160
-170
-170
10k
100k
1M
10M
100M
1k
toc13
10M
150
230
140
210
130
190
120
110
100
90
80
TA = +25˚C
70
TA = -40˚C
10
150
130
110
260
TA = -40˚C
10
100
1k
FREQUENCY (MHz)
TA = +25˚C
TA = +85˚C
80
00
01
10
11
PWR SETTING
toc17
3.85
FASTLOCK OFF
3.84
FASTLOCK ON
3.83
220
200
180
160
3.82
3.81
3.8
3.79
3.78
140
3.77
120
3.76
FREQUENCY (MHz)
120
PLL LOCK vs. TIME
240
1K
140
10k
TA = +85˚C
100
160
TA = -40˚C
FREQUENCY (GHz)
SUPPLY CURRENT (mA)
280
TA = +25˚C
100M
toc15
100
toc16
300
10M
180
TA = -40˚C
70
11
1M
200
170
50
100k
SUPPLY CURRENT vs. OUTPUT POWER
SETTING (TWO CHANNELS ACTIVE, 3GHz)
TA = +85˚C
SUPPLY CURRENT vs. FREQUENCY
(TWO CHANNELS ACTIVE,
MAXIMUM OUTPUT POWER)
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10k
TA = +25˚C
PWR SETTING
10
1k
FREQUENCY (Hz)
90
TA = +85˚C
100
-170
100M
toc14
250
SUPPLY CURRENT (mA)
SUPPLY CURRENT (mA)
160
01
1M
SUPPLY CURRENT vs. FREQUENCY
(ONE CHANNEL ACTIVE,
MAXIMUM OUTPUT POWER)
SUPPLY CURRENT vs. OUTPUT POWER
SETTING (ONE CHANNEL ACTIVE, 3GHz)
00
100k
FREQUENCY (Hz)
FREQUENCY (Hz)
60
10k
SUPPLY CURRENT (mA)
1k
toc12
-70
-80
PHASE NOISE (dBc/Hz)
PHASE NOISE (dBc/Hz)
-70
2679.4MHz FRACTIONAL-N PHASE NOISE
vs. FREQUENCY (LOW-SPUR MODE)
10K
3.75
0
50
100
TIME (µs)
150
200
Maxim Integrated │ 7
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Operating Characteristics Testing Conditions Table
TOC TITLE
fREF
(MHz)
3.0GHz VCO
OPEN-LOOP
PHASE NOISE
vs. FREQUENCY
4.5GHz VCO
OPEN-LOOP
PHASE NOISE
vs. FREQUENCY
6.0GHz VCO
OPEN-LOOP
PHASE NOISE
vs. FREQUENCY
3.0GHz
CLOSED-LOOP
PHASE NOISE
vs. FREQUENCY
4.5GHz
CLOSED-LOOP
PHASE NOISE
vs. FREQUENCY
6.0GHz
CLOSED-LOOP
PHASE NOISE
vs. FREQUENCY
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N/A
N/A
N/A
50
50
50
fPFD
(MHz)
REGISTER
SETTINGS
(hex)
LOOP
FILTER
BW (Hz)
MAX2871 EV KIT COMPONENT VALUES
C2
(F)
R2A +
R2B (I)
C1
(F)
N/A
80B40000,
80000141,
0000405A,
XX00013,
648020FC,
00000005
N/A
80B40000,
80000141,
0000405A,
XX00013
648020FC,
00000005
N/A
80B40000,
80000141
0000405A
XX00013,
648020FC
00000005
N/A
N/A
N/A
N/A
25
803C0000
80000141
00009E42,
E8000013,
618160FC,
00400005
40k
0.1F
120
25
805A0000,
80000141,
00009E42,
E8000013,
618160FC,
00400005
40k
0.1F
25
80780000,
80000141,
00009E42,
EA000013,
608C80FC,
00400005
40k
0.1F
N/A
N/A
N/A
N/A
R3
(I)
C3
(F)
COMMENTS
N/A
VCO bits set
for 3GHz
output,
VAS_SHDN = 1
N/A
VCO bits set
for 4.5GHz
output,
VAS_SHDN = 1
N/A
N/A
VCO bits set
for 6.0GHz
output,
VAS_SHDN = 1
0.012F
250
820p
120
0.012F
250
820p
120
0.012F
250
820p
N/A
N/A
N/A
N/A
N/A
N/A
Maxim Integrated │ 8
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Operating Characteristics Testing Conditions Table (continued)
TOC TITLE
fREF
(MHz)
904MHz INTEGER-N
MODE PHASE
NOISE AND SPUR
PERFOMANCE
vs. FREQUENCY
2687.5MHz
INTEGER-N PHASE
NOISE
AND SPUR
PERFORMANCE vs.
FREQUENCY
2113.5MHz
FRACTIONAL-N
PHASE NOISE
(LOW-NOISE MODE)
vs. FREQUENCY
2113.5MHz
FRACTIONAL-N
PHASE NOISE vs.
FREQUENCY
(LOW-SPUR MODE)
2679.4MHz
FRACTIONAL-N
PHASE NOISE vs.
FREQUENCY
(LOW-NOISE MODE)
2679.4MHz
FRACTIONAL-N
PHASE NOISE vs.
FREQUENCY
(LOW-SPUR MODE)
SUPPLY CURRENT
vs. OUTPUT POWER
SETTING
(ONE CHANNEL
ACTIVE, 3GHz)
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40
40
50
50
50
50
50
fPFD
(MHz)
REGISTER
SETTINGS
(hex)
LOOP
FILTER
BW (Hz)
MAX2871 EV KIT COMPONENT VALUES S
C2
(F)
R2A +
R2B (I)
C1
(F)
R3
(I)
C3
(F)
0.8
82350000,
800007D1
E1065FC2,
2C000013
6020803C
00400005
16k
0.1F
806
3300p
1201
470p
0.5
94FF0000,
803207D1,
010A1E42,
B00000A3,
6090803C,
00400005
5k
0.1F
1000
6800p
300
0.01F
25
00548050,
400003E9,
81005FC2,
E8000013,
609C80FC,
00400005
40k
0.1F
120
0.012F
250
820p
25
00548050,
400003E9,
E1005FC2,
E8000013,
609C80FC,
00400005
40k
0.1F
120
0.012F
250
820p
25
00358160,
203207D1,
01005E42,
B20000A3,
6010003C,
00400005
40k
0.1F
120
0.012F
250
820p
25
00358160,
203207D1,
41005E42,
B20000A3,
6010003C,
00400005
40k
0.1F
120
0.012F
250
820p
25
003C0000,
20000321,
01005E42,
00000013,
610F423C,
01400005,
COMMENTS
APWR swept
from 00 to 11
Maxim Integrated │ 9
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Operating Characteristics Testing Conditions Table (continued)
TOC TITLE
fREF
(MHz)
SUPPLY CURRENT
vs. FREQUENCY
(ONE CHANNEL
ACTIVE, MAXIMUM
OUTPUT POWER)
SUPPLY CURRENT
vs. OUTPUT POWER
SETTING (TWO
CHANNELS ACTIVE)
SUPPLY CURRENT
vs. FREQUENCY
(TWO CHANNELS
ACTIVE MAXIMUM
OUTPUT POWER)
PLL LOCK vs. TIME
www.maximintegrated.com
50
50
50
40
fPFD
(MHz)
REGISTER
SETTINGS
(hex)
LOOP
FILTER
BW (Hz)
MAX2871 EV KIT COMPONENT VALUES
C2
(F)
R2A +
R2B (I)
C1
(F)
R3
(I)
C3
(F)
COMMENTS
25
003C0000,
20000321,
01005E42,
00000013,
610F423C,
01400005
N and F values
changed for
each frequency
25
003C0000,
20000321,
01005E42,
00000013,
610F43FC,
01400005
APWR and
BPWR swept
from 00 to 11
25
003C0000,
20000321,
01005E42,
00000013,
610F43FC,
01400005
N and F values
swept for each
frequency
40
00250120,
20320141,
00004042,
000000A3,
0184023C,
01400005
40k
0.1F
120
0.012F
250
820p
CDM changed
from 00 to 01
Maxim Integrated │ 10
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
BIAS_FILT
RSET
GND_TUNE
TUNE
NOISE_FILT
GND_VCO
VCC_VCO
TOP VIEW
REG
Pin Configuration
24
23
22
21
20
19
18
17
LD 25
16
VCC_RF
RFOUT_EN 26
15
RFOUTB_N
GND_DIG 27
14
RFOUTB_P
13
RFOUTA_N
12
RFOUTA_P
11
GND_RF
VCC_DIG 28
MAX2871
REF_IN 29
MUX 30
+
1
2
3
4
5
6
7
CLK
DATA
LE
CE
SW
VCC_CP
CP_OUT
VDD_SD 32
10
VCC_PLL
9
GND_PLL
8
GND_CP
GND_SD 31
EP
TQFN
Pin Description
PIN
NAME
FUNCTION
1
CLK
Serial Clock Input. The data is latched into the 32-bit shift register on the rising edge of the
CLK line.
2
DATA
Serial Data Input. The serial data is loaded MSB first. The 3 LSBs identify the register address.
3
LE
Load Enable Input. When LE goes high the data stored in the shift register is loaded into the
appropriate latches.
4
CE
Chip Enable. A logic-low powers the part down and the charge pump becomes high impedance.
5
SW
Fast-Lock Switch. Connect to the loop filter when using the fast-lock mode. No connect in
Normal mode
6
VCC_CP
Power Supply for Charge Pump. Place decoupling capacitors as close as possible to the pin.
7
CP_OUT
Charge-Pump Output. Connect to external loop filter input.
8
GND_CP
Ground for Charge-Pump. Connect to board ground, not to the paddle.
9
GND_PLL
Ground for PLL. Connect to board ground, not to the paddle.
10
VCC_PLL
Power Supply for PLL. Place decoupling capacitors as close as possible to the pin.
11
GND_RF
Ground for RF Outputs. Connect to board ground plane, not to the paddle.
12
RFOUTA_P
Open Collector Positive RF Output A. See RFOUTA± and RFOUTB± section in Detailed
Description.
13
RFOUTA_N
Open Collector Negative RF Output A. See RFOUTA± and RFOUTB± section in Detailed
Description.
www.maximintegrated.com
Maxim Integrated │ 11
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Pin Description (continued)
PIN
NAME
14
RFOUTB_P
Open Collector Positive RF Output B. See RFOUTA± and RFOUTB± section in Detailed
Description.
15
RFOUTB_N
Open Collector Negative RF Output B. See RFOUTA± and RFOUTB± section in Detailed
Description.
16
VCC_RF
17
VCC_VCO
18
GND_VCO
19
NOISE_FILT
VCO Noise Decoupling. Place a 1µF capacitor to ground.
20
TUNE
Control Input to the VCO. Connect to external loop filter.
21
GND_TUNE
22
RSET
23
BIAS_FILT
24
REG
25
LD
26
RFOUT_EN
27
GND_DIG
Ground for Digital Circuitry. Connect to main board ground plane, not directly to the paddle.
28
VCC_DIG
Power Supply for Digital Circuitry. Place decoupling capacitors as close as possible to pin.
29
REF_IN
Reference Frequency Input. This is a high-impedance input with a nominal bias voltage of VCC_
DIG/2. AC-couple to reference signal.
30
MUX
31
GND_SD
Ground for Sigma-Delta Modulator. Connect to main board ground plane, not directly to
the paddle.
32
VCC_SD
Power Supply for Sigma-Delta Modulator. Place decoupling capacitors as close as possible
to the pin.
—
EP
www.maximintegrated.com
FUNCTION
Power Supply for RF Output and Dividers. Place decoupling capacitors as close as possible to
the pin.
VCO Power Supply. Place decoupling capacitors to the analog ground plane.
Ground for VCO. Connect to main board ground plane, not directly to the paddle.
Ground for Control Input to the VCO. Connect to main board ground plane, not directly to the
paddle.
Charge-Pump Current Range Input. Connect an external resistor to ground to set the minimum
CP current. ICP = 1.63/RSET x (1 + CP[3:0])
VCO Noise Decoupling. Place a 1µF capacitor to ground.
Reference Voltage Compensation. Place a 1µF capacitor to ground.
Lock Detect Output. Logic-high when locked, and logic-low when unlocked. See register
description for more details (Table 9).
RF Output Enable. A logic-low disables the RF outputs.
Multiplexed I/Os. See Table 5.
Exposed Pad. Connect to board ground.
Maxim Integrated │ 12
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Detailed Description
● Register 4, set bit 5 and 8 to 0 to keep RFOUT disable.
● Register 3, Address 0X03
4-Wire Serial Interface
The MAX2871 can be controlled by 3-wire SPI for write
operation using CLK, DATA, LE pins, refer Figure 1. For
read operation, in addition to the above 3 pins, MUX pin
can be used to access Reg, 0x06, refer Figure 2. The
MAX2871 serial interface contains six write-only and
one read-only 32-bit registers. The 29 most-significant
bits (MSBs) are data, and the three least-significant bits
(LSBs) are the register address. Register data is loaded
MSB first through the 4-wire serial interface (SPI). When
LE is logic-low, the logic level at DATA is shifted at the rising edge of CLK. At the rising edge of LE, the 29 data bits
are latched into the register selected by the address bits.
The user must program all register values after power-up.
● Register 2, Address 0X02
● Register 1, Address 0X01
● Register 0, Address 0X00
To enable RFOUT, Register 4, Address 0X04, set bit 5
and 8 to 1.
Register programming order should be address 0x05,
0x04, 0x03, 0x02, 0x01, and 0x00. Several bits are
double buffered to update the settings at the same time.
See the register descriptions for double buffered settings.
Read Sequence
● Register 4, set bit 5 and 8 to 0 to keep RFOUT disable.
Register 0x06 can be read back through the MUX pin.
The user must set MUX (register 5, bit 18 and register
2, bits 28:26) = 1100. To begin the read sequence, set
LE to logic-low, send 32 periods of CLK, and set LE to
logic-high. While the CLK is running, the DATA pin can
be held at logic-high or logic-low for 29 clocks, but the
last 3 bits must be 110 to indicate register 6, then set LE
back to logic-high after the 32nd clock. Finally, send 1
period of the clock. The MSB of register 0x06 appears
after the rising edge of the next clock and continues to
shift out for the next 29 clock cycles (Figure 2). After the
LSB of register 0x06 has been read, the user can reset
MUX register = 0000.
● Register 3, Address 0X03
Power Modes
Upon power-up, the registers should be programmed
twice with at least a 20ms pause between cycle of
write. The first write ensures that the device is enabled,
and the second write starts the VCO selection process. Recommended to turn-off the outputs during this
sequence and then turn-on the outputs using RFA_EN,
RFB_EN.
For a clean clock at start up, after power on, follow this
sequence of programming:
● Register 5, Address 0X05. Wait 20ms
● Register 2, Address 0X02
The MAX2871 can be put into low-power mode by setting
SHDN = 1 (register 2, bit 5) or by setting the CE pin to logic-low. In low-power mode, all blocks except SPI are off.
● Register 1, Address 0X01
● Register 0, Address 0X00
● Register 5, Address 0X05
t LES
t LEH
t CP
LE
t LEW
t CL
CLK
t CH
tDS
DATA
BIT31
t DH
BIT30
BIT1
BIT0
Figure 1. SPI Timing Diagram
www.maximintegrated.com
Maxim Integrated │ 13
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
DATA
DON’T CARE
1
0
1
LE
CLK
1
29
30
31
32
33
34
35
36
MSB of R 6
MU X
tDOT
Figure 2. Initiating Readback
REF_IN
X2
MUX
R COUNTER
DIVIDE-BY-2
MUX
To PFD
Figure 3. Reference Input
After exiting low-power mode, allow at least 20ms for
external capacitors to charge to their final values before
programming the final VCO frequency.
140MHz for int-N mode. The R-divider can be held in reset
when RST (register 2, bit 3) = 1.
Reference Input
The VCO frequency (fVCO), N, F, and M can be determined based on desired RF output frequency (fRFOUTA)
as follows:
The reference input stage is configured as a CMOS
inverter with shunt resistance from input to output. In shutdown mode this input is set to high impedance to prevent
loading of the reference source.
The reference input signal path also includes optional x2
and ÷2 blocks. When the reference doubler is enabled
(DBR = 1), the maximum reference input frequency is limited to 105MHz. When the doubler is disabled, the reference input frequency is limited to 210MHz. The minimum
reference frequency is 10MHz. The minimum R counter
divide ratio is 1, and the maximum divide ratio is 1023.
PFD Frequency
The phase-detector frequency is determined as follows:
fPFD = fREF x [(1 + DBR)/(R x (1 + RDIV2))]
fREF represents the external reference input frequency.
DBR (register 2, bit 25) sets the fREF input frequency doubler mode (0 or 1). RDIV2 (register 2, bit 24) sets the fREF
divide-by-2 mode (0 or 1). R (register 2, bits 23:14) is the
value of the 10-bit programmable reference counter (1 to
1023). The maximum fPFD is 125MHz for frac-N mode and
www.maximintegrated.com
Int, Frac, Mod, and R Counter Relationship
Set DIVA value property based on fRFOUTA and Table 4
(register 4, bits 22:20)
fVCO = fRFOUTA x DIVA
If bit FB = 1, (DIVA is not in PLL feedback loop):
N + (F/M) = fVCO/fPFD
If bit FB = 0, (DIVA is in PLL feedback loop) and DIVA ≤
16:
N + (F/M) = (fVCO/fPFD)/DIVA
If bit FB = 0, (DIVA is in PLL feedback loop) and DIVA > 16:
N + (F/M) = (fVCO/fPFD)/16
N is the value of the 16-bit N counter (16 to 65535), programmable through bits 30:15 of register 0. M is the fractional modulus value (2 to 4095), programmable through
bits 14:3 of register 1. F is the fractional division value (0
to MOD - 1), programmable through bits 14:3 of register 0.
In frac-N mode, the minimum N value is 19 and maximum
Maxim Integrated │ 14
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
N value is 4091. The N counter is held in reset when RST
= 1 (register 2, bit 3). DIVA is the RF output divider setting
(0 to 7), programmable through bits 22:20 of register 4.
The division ratio is set by 2DIVA.
The RF B output frequency is determined as follows:
The charge-pump output can be put into high-impedance
mode when TRI = 1 (register 2, bit 4). The output is in
normal mode when TRI = 0.
The phase detector polarity can be changed if an active
inverting loop filter topology is used. For noninverting loop
filters, set PDP = 1 (register 2, bit 6). For inverting loop
filters, set PDP = 0.
If BDIV = 0 (register 4, bit 9), fRFOUTB = fRFOUTA.
If BDIV = 1, fRFOUTB = fVCO.
MUX
Int-N/Frac-N Modes
MUX is a multipurpose input/output for observing and
controlling various internal functions of the MAX2871.
MUX can also be configured as serial data output. Bits
MUX (register 5, bit 18 and register 2, bit 28:26) are used
to select the desired MUX function (see Table 5).
Integer-N mode is selected by setting bit INT = 1 (register
0, bit 31). When operating in integer-N mode, it is also
necessary to set bit LDF (register 2, bit 8) to set the lock
detect to integer-N mode.
The device’s frac-N mode is selected by setting bit INT = 0
(register 0, bit 31). Additionally, set bit LDF = 0 (register 2,
bit 8) for frac-N lock-detect mode.
Lock Detect
Lock detect can be monitored through the LD output by
setting the LD bits (register 5, bits 23:22). For digital lock
detect, set LD = 01. The digital lock detect is dependent
on the mode of the synthesizer. In frac-N mode set LDF =
0, and in int-N mode set LDF = 1. To set the accuracy of
the digital lock detect, see Table 1 and Table 2.
If the device is in frac-N mode, it will remain in frac-N
mode when fractional division value F = 0, which can
result in unwanted spurs. To avoid this condition, the
device can automatically switch to integer-N mode when
F = 0 if the bit F01 = 1 (register 5, bit 24).
Analog lock detect can be set with LD = 10. In this mode,
LD is an open-drain output and requires an external
pullup resistor of 10kΩ typical value.
Phase Detector and Charge Pump
The device’s charge-pump current is determined by the
value of the resistor from pin RSET to ground and the
value of bits CP (register 2, bits 12:9) as follows:
The lock detect output validity is dependent on many
factors. The lock detect output is not valid during VCO
auto selection process. After the VCO auto selection
process has completed, the lock detect output is not
valid until the TUNE voltage has settled. TUNE voltage
settling time is dependent on loop filter bandwidth, and
can be calculated using EE-Sim Simulation tool found at
www.maximintegrated.com.
ICP = 1.63/RSET x (1+ CP)
To reduce spurious in frac-N mode, set charge-pump
linearity bits CPL = 00/01/10/11 (register 1, bits 30:29).
The user can determine which mode works best for their
application. For int-N mode, set CPL = 00.
Table 1. Frac-N Digital Lock-Detect Settings
PFD FREQUENCY
LDS
LDP
LOCKED UP/DOWN
TIME SKEW (ns)
NUMBER OF LOCKED
CYCLES TO SET LD
UP/DOWN TIME SKEW
TO UNSET LD (ns)
≤ 32MHz
0
0
10
40
15
≤ 32MHz
0
1
6
40
15
> 32MHz
1
X
4
40
4
Table 2. Int-N Digital Lock-Detect Settings
PFD FREQUENCY
LDS
LDP
LOCKED UP/DOWN
TIME SKEW (ns)
NUMBER OF LOCKED
CYCLES TO SET LD
UP/DOWN TIME SKEW
TO UNSET LD (ns)
≤ 32MHz
0
0
10
5
15
≤ 32MHz
0
1
6
5
15
> 32MHz
1
X
4
5
4
www.maximintegrated.com
Maxim Integrated │ 15
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Cycle Slip Reduction
Cycle slip reduction is one of the two methods available to
improve lock time. It is enabled by setting CSM bit (register
3, bit 18) to 1. In this mode, the charge pump must be set
to its minimum value.
R3
C3
Fast-Lock
Another method to decrease lock time is to use a fast-lock
mode. This mode requires that CP = 0000 (register 2,
bits 12:9) and that the shunt resistive portion of the loop
filter be segmented into two parts, where one resistor
(R2A) is 1/4 of the total resistance, and the other resistor
(R2B) is 3/4 of the total resistance. The larger resistor
(R2B) should be connected from SW to Ground, and the
smaller resistor (R2A) from SW to the loop filter capacitor
(see Figure 4). When CDM = 01 (register 3, bits 16:15),
fast-lock is active after the VAS has completed. During
fast-lock, the charge pump is increased to CP = 1111 and
the shunt loop filter resistance is set to 1/4 of the total
resistance by changing pin SW from high impedance to
ground. Fast-lock deactivates after a timeout set by the
user. This timeout is loop filter dependent, and is set by:
tFAST-LOCK = M x CDIV/fPFD
where M is the modulus setting and CDIV is the clock
divider setting. The user must determine the CDIV setting
based on their loop filter time constant. The SW pin can
be left open/ no connect when fast lock mode is not used.
RFOUTA± and RFOUTB±
The device has dual differential open-collector RF outputs that require an external RF choke or a 50Ω resistor
to supply for each output. Each differential output can
be independently enabled or disabled by setting bits
RFA_EN (register 4, bit 5) and RFB_EN (register 4, bit 8).
Both outputs are also controlled by applying a logic-high
(enabled) or logic-low (disabled) to pin RFOUT_EN.
The output power of each output can be individually controlled with APWR (register 4, bits 4:3) for RFOUTA and
BPWR (register 4, bits 7:6) for RFOUTB. The available differential output power settings are from -4dBm to +5dBm,
in 3dB steps with 50Ω pullup to supply. The available
single-ended output power ranges from -4dBm to +5dBm
in 3dB steps with a RF choke to supply. Across the entire
frequency range different pullup elements (L or R) are
required for optimal output power. If single-ended output
is used, the unused output should be supplied and terminated in the same manner as the corresponding load. If a
differential output is unused then those RFOUT pins should
be directly connected to VCC_RF (pin 16).
www.maximintegrated.com
CP_OUT
7
C2
C1
MAX2871
R2A
5
SW
20
TUNE
R2B
Figure 4. Fast Lock Filter Topology
To prevent undesired frequencies from being output while
acquiring lock, the output power can be disabled when
the PLL is unlocked by using MTLD (register 4, bit 10). A
logic 1 will disable the outputs when the digital lock detect
is logic low. When acquiring lock the output can overshoot and pass through the desired frequency. In some
circumstances, the digital lock detect will flicker high during these periods. To prevent this from happening, a timer
can be used to delay the output from enabling after losing
lock. Enable MUTEDEL (register 3, bit 17) with MTLD
enabled to use this function. The delay for enabling the
output is set by:
Delay = CDIV x M/fPFD
where CDIV (register 3, bits 14:3) is the clock divider,
M (register 1, bits 14:3) is the variable modulus for the
fractional N modulator, and fPFD is the phase detector
frequency.
Voltage-Controlled Oscillator
The fundamental VCO frequency of the device guarantees
gap-free coverage from 3.0GHz to 6.0GHz using four
individual VCO core blocks with 16 sub-bands within each
block. Connect the output of the loop filter to the TUNE
input. The TUNE input is used to control the VCO.
Maxim Integrated │ 16
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Tune ADC
If VAS_SHDN = 1, then the VCO can be manually
selected by bits VCO (register 3, bits 31:26). Refer to
Applications Information for detailed implementation of
VCO manual selection.
1) Set bits CDIV (register 3, bits 14:3) = fPFD/100kHz to
set the clock speed for the ADC.
Phase Adjustment
A 7-bit ADC is used to read back the VCO tuning voltage.
The ADC value can be read back through register 6, bits
22:16. To digitize the tuning voltage, do the following:
2) Set bits ADCM (register 5, bits 5:3) = 100 to enable
the ADC to read the TUNE pin voltage.
3) Set bit ADCS (register 5, bit 6) = 1 to start the ADC
conversion process.
4) Wait 100µs for the conversion process to finalize.
5) Read back register 6. The ADC value is located in bits
22:16.
6) Reset bits ADCM = 0 and ADCS = 0.
The voltage on the TUNE pin can be calculated as:
V = 0.315 + ADC x 0.0165
VCO Autoselect (VAS) State Machine
An internal VCO autoselect state machine is initiated
when register 0 is programmed to automatically select
the correct VCO if bit VAS_SHDN = 0 (register 3, bit 25).
The state machine clock, fBS, must be set to 50kHz. This
is set by the BS bits (register 4, bits 25:24, 19:12). The
formula for setting BS is:
BS = fPFD/50kHz
where fPFD is the phase-detector frequency. The BS value
should be rounded to the nearest integer. If the calculated BS is higher than 1023, then set BS = 1023. If fPFD
is lower than 50kHz, then set BS = 1. The time needed to
select the correct VCO is 10/fBS.
The VAS_TEMP bit (register 3, bit 24) can be used to
select the best VCO for the given ambient temperature
to ensure that the VCO will not drift out of lock if the temperature changes within -40°C to +85°C. Bits RFA_EN
(register 4, bit 5) and RFB_EN (register 4, bit 8) must be
0, and bits 30:29 of register 5 must be set to 11 during
VCO acquisition. Setting VAS_TEMP = 1 will increase the
time needed to achieve lock from 10/fBS to approximately
100ms.
www.maximintegrated.com
After achieving lock, the phase of the single MAX2871
device’s RF output can be changed in increments of P
(register 1, bits 26:15) /M (register 1, bits 14:3) x 360°.
Also, multiple MAX2871 devices’ RF Outputs can be
phase synchronized with a single reference input. See
Applications Information for detailed implementation.
Low-Spur Mode
The device offers three modes for the sigma-delta modulator. Low-noise mode offers lower in-band noise at the
expense of spurs. The spurs can be reduced by setting
SDN = 10 (register 2, bits 30:29) or SDN = 11 for different
modes of dithering. The user can determine which mode
works best for their application.
Temperature Sensor
The device is equipped with an on-chip temperature sensor and 7-bit ADC.
To read the digitized output of the temperature sensor:
1) Set bits CDIV (register 3, bits 14:3) = fPFD/100kHz to
set the clock speed for the ADC.
2) Set bits ADCM (register 5, bits 5:3) = 001 to enable the
ADC to read the temperature.
3) Set bit ADCS (register 5, bit 6) = 1 to start the ADC
conversion process.
4) Wait 100µs for the conversion process to finalize.
5) Read back register 6. The ADC value is located in bits
22:16.
6) Reset bits ADCM=0 and ADCS=0.
The approximate ambient temperature can be converted
as:
t = 95 – 1.14 x ADC
This formula is most accurate when the VCO is enabled
and RFOUTA is enabled at full output power. The temperature can vary based on output power and if one or
both outputs are enabled.
Maxim Integrated │ 17
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Register and Bit Descriptions
The operating mode of the device is controlled by six onchip registers.
Defaults are not guaranteed upon power-up and are
provided for reference only. All reserved bits should only
be written with default values. In low-power mode, the
register values are retained. Upon power-up, the registers
should be programmed twice with at least a 20ms pause
between writes. The first write ensures that the device is
enabled, and the second write starts the VCO selection
process.
Table 3. Register 0 (Address: 000, Default: 007D0000HEX)
BIT LOCATION
BIT ID
DEFINITION
INT
Int-N or Frac-N
Mode Control
0 = Enables the fractional-N mode
1 = Enables the integer-N mode
The LDF bit must also be set to the appropriate mode.
N[15:0]
Integer Division
Value
Sets integer part (N-divider) of the feedback divider factor. All integer
values from 16 to 65,535 are allowed for integer mode. Integer values
from 0 to 15 are not allowed. Integer values from 19 to 4091 are allowed
for fractional mode.
31
30:15
NAME
14:3
FRAC[11:0]
Fractional
Division Value
2:0
ADDR[2:0]
Address Bits
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Sets fractional value:
000000000000 = 0 (see F0I bit description)
000000000001 = 1
---111111111110 = 4094
111111111111 = 4095
Control Register address bits, 000
Maxim Integrated │ 18
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 4. Register 1 (Address: 001, Default: 2000FFF9HEX)
BIT LOCATION
BIT ID
NAME
31
Reserved
Reserved
30:29
28:27
26:15
CPL[1:0]
CP Linearity
CPT[1:0]
Charge Pump
Test
P[11:0]
Phase Value
14:3
M[11:0]
Modulus Value
(M)
2:0
ADDR[2:0]
Address Bits
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DEFINITION
Reserved. Program to 0.
Sets CP linearity mode.
00 = Disables the CP linearity mode (integer-N mode)
01 = CP linearity 10% mode (frac-N mode)
10 = CP linearity 20% mode (frac-N mode)
11 = CP linearity 30% mode (frac-N mode)
Sets charge-pump test modes.
00 = Normal mode
01 = Long Reset mode
10 = Force CP into source mode
11 = Force CP into sink mode
Sets phase value. See the Phase Adjustment section.
000000000000 = 0
000000000001 = 1 (recommended)
----111111111111 = 4095
Fractional modulus value used to program fVCO. See the Int, Frac, Mod
and R Counter Relationship section. Double buffered by register 0.
000000000000 = Not Valid
000000000001 = Not Valid
000000000010 = 2
----111111111111 = 4095
Control Register address bits, 001
Maxim Integrated │ 19
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 5. Register 2 (Address: 010, Default: 00004042HEX)
BIT LOCATION
BIT ID
NAME
31
LDS
Lock-Detect
Speed
SDN[1:0]
Frac-N Sigma
Delta Noise
Mode
Sets noise mode (see the Low-Spur Mode section.)
00 = Low-noise mode
01 = Reserved
10 = Low-spur mode 1
11 = Low-spur mode 2
30:29
DEFINITION
Lock-detect speed adjustment.
0 = fPFD ≤ 32MHz
1 = fPFD > 32MHz
28:26
MUX[2:0]
MUX
Configuration
Sets MUX pin configuration (MSB bit located register 05).
0000 = Three-state output
0001 = D_VDD
0010 = D_GND
0011 = R-divider output
0100 = N-divider output/2
0101 = Analog lock detect
0110 = Digital lock detect
0111 = Sync Input
1000 : 1011 = Reserved
1100 = Read SPI registers 06
1101 : 1111= Reserved
25
DBR
Reference
Doubler Mode
Sets reference doubler mode.
0 = Disable reference doubler
1 = Enable reference doubler
24
RDIV2
Reference Div2
Mode
R[9:0]
Reference
Divider Mode
23:14
www.maximintegrated.com
Sets reference divide-by-2 mode.
0 = Disable reference divide-by-2
1 = Enable reference divide-by-2
Sets reference divide value (R). Double buffered by register 0.
0000000000 = 0 (unused)
0000000001 = 1
----1111111111 = 1023
Maxim Integrated │ 20
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 5. Register 2 (Address: 010, Default: 00004042HEX) (continued)
BIT LOCATION
BIT ID
NAME
13
REG4DB
Double Buffer
Sets double buffer mode.
0 = Disabled
1 = Enabled
12:9
CP[3:0]
Charge-Pump
Current
Sets charge-pump current in mA (RSET = 5.1kΩ). Double buffered by
register 0.
ICP = 1.63/RSET × (1+CP[3:0])
8
LDF
Lock-Detect
Function
Sets lock-detect function.
0 = Frac-N lock detect
1 = Int-N lock detect
7
LDP
Lock-Detect
Precision
Sets lock-detect precision.
0 = 10ns
1 = 6ns
6
PDP
Phase Detector
Polarity
5
SHDN
Shutdown
Mode
4
TRI
Charge Pump
Output HighImpedance
Mode
Sets charge-pump output high-impedance mode.
0 = Disabled
1 = Enabled
3
RST
Counter Reset
Sets counter reset mode.
0 = Normal operation
1 = R and N counters reset
2:0
ADDR[2:0]
Address Bits
www.maximintegrated.com
DEFINITION
Sets phase detector polarity.
0 = Negative
1 = Positive (default)
Sets power-down mode.
0 = Normal mode
1 = Device shutdown
Control Register address bits, 010
Maxim Integrated │ 21
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 6. Register 3 (Address: 011, Default: 0000000BHEX)
BIT LOCATION
BIT ID
NAME
DEFINITION
Manual selection of VCO and VCO sub-band when VAS is disabled.
000000 = VCO0
….
111111 = VCO63
31:26
VCO[5:0]
VCO
25
VAS_SHDN
VAS_SHDN
Sets VAS shutdown mode.
0 = VAS enabled
1 = VAS disabled
24
VAS_TEMP
VAS_TEMP
Sets VAS response to temperature drift.
0 = VAS temperature compensation disabled
1 = VAS temperature compensation enabled
23:19
Reserved
Reserved
Reserved.
18
CSM
Cycle Slip
Mode
Cycle Slip Mode
0 = Disable Cycle Slip Reduction
1 = Enable Cycle Slip Reduction
17
MUTEDEL
Mute Delay
Mode
16:15
CDM[1:0]
Mute Delay
0 = Do not delay LD to MTLD function to prevent flickering
1= Delay LD to MTLD function to prevent flickering
Clock Divider
Mode
Sets clock divider mode.
00 = Mute until Lock Delay
01 = Fast-lock enabled
10 = Phase Adjustment mode
11 = Reserved
14:3
CDIV[11:0]
Clock Divider
Value
Sets 12-bit clock divider value.
000000000000 = Unused
000000000001 = 1
000000000010 = 2
----111111111111 = 4095
2:0
ADDR[2:0]
Address Bits
Control Register address bits, 011
www.maximintegrated.com
Maxim Integrated │ 22
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 7. Register 4 (Address: 100, Default: 6180B23CHEX)
BIT LOCATION
BIT ID
NAME
31:29
Reserved
Reserved
28
SDLDO
Shutdown VCO
LDO
Sets Shutdown VCO LDO mode.
0 = Enables LDO
1 = Disables LDO
27
SDDIV
Shutdown VCO
Divider
Sets Shutdown VCO Divider mode.
0 = Enables VCO Divider
1 = Disables VCO Divider
26
SDREF
Shutdown
Reference Input
Sets Shutdown Reference input mode.
0 = Enables Reference Input
1 = Disables Reference Input
25:24
BS[9:8]
23
FB
22:20
DIVA[2:0]
DEFINITION
Reserved. Program to 011.
Band-Select MSBs Sets Band-Select clock divider MSBs. See bits[19:12].
VCO Feedback
Mode
Sets VCO to N counter feedback mode.
0 = Divided
1 = Fundamental
RFOUT_ Output
Divider Mode
Sets RFOUT_ output divider mode. Double buffered by register 0 when
REG4DB = 1.
000 = Divide by 1, if 3000MHz ≤ fRFOUTA ≤ 6000MHz
001 = Divide by 2, if 1500MHz ≤ fRFOUTA < 3000MHz
010 = Divide by 4, if 750MHz ≤ fRFOUTA < 1500MHz
011 = Divide by 8, if 375MHz ≤ fRFOUTA < 750MHz
100 = Divide by 16, if 187.5MHz ≤ fRFOUTA < 375MHz
101 = Divide by 32, if 93.75MHz ≤ fRFOUTA < 187.5MHz
110 = Divide by 64, if 46.875MHz ≤ fRFOUTA < 93.75MHz
111 = Divide by 128, if 23.5MHz ≤ fRFOUTA< 46.875MHz
Sets band select clock divider value. MSB are located in bits [25:24].
0000000000 = Reserved
0000000001 =1
0000000010 = 2
---1111111111 = 1023
19:12
BS[7:0]
Band Select
11
SDVCO
VCO Shutdown
10
MTLD
RFOUT Mute until
Lock Detect
9
BDIV
RFOUTB Output
Path Select
Sets RFOUTB output path select.
0 = VCO divided output
1 = VCO fundamental frequency
8
RFB_EN
RFOUTB Output
Mode
Sets RFOUTB output mode.
0 = Disabled
1 = Enabled
RFOUTB Output
Power
Sets RFOUTB single-ended output power. See the RFOUTA± and
RFOUTB± section.
00 = -4dBm
01 = -1dBm
10 = +2dBm
11 = +5dBm
7:6
BPWR[1:0]
www.maximintegrated.com
Sets VCO Shutdown mode.
0 = Enables VCO
1 = Disables VCO
Sets RFOUT Mute until Lock Detect Mode
0 = Disables RFOUT Mute until Lock Detect Mode
1 = Enables RFOUT Mute until Lock Detect Mode
Maxim Integrated │ 23
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 7. Register 4 (Address: 100, Default: 6180B23CHEX) (continued)
BIT LOCATION
BIT ID
NAME
5
RFA_EN
RFOUTA Output
Mode
4:3
APWR[1:0]
RFOUTA Output
Power
2:0
C[2:0]
Register Address
DEFINITION
Sets RFOUTA output mode.
0 = Disabled
1 = Enabled
Sets RFOUTA single-ended output power. See the RFOUTA± and
RFOUTB± section.
00 = -4dBm
01 = -1dBm
10 = +2dBm
11 = +5dBm
Control Register address bits, 100
Table 8. Register 5 (Address: 101, Default: 00400005HEX)
BIT LOCATION
BIT ID
NAME
31
Reserved
Reserved
Reserved. Program to 0.
30:29
VAS_DLY
VAS_DLY
VCO Autoselect Delay.
Program to 11 when VAS_TEMP=1
Program to 00 when VAS_TEMP=0
28:26
Reserved
Reserved
Reserved. Program to 000.
25
SDPLL
Shutdown PLL
Sets Shutdown PLL mode.
0 = Enables PLL
1 = Disables PLL
24
F01
F01
23:22
LD[1:0]
Lock-Detect Pin
Function
21:19
Reserved
Reserved
Reserved. Program to 000.
18
17:7
MUX[3]
Reserved
MUX MSB
Reserved
Sets mode at MUX pin (see register 2 [28:26])
Reserved. Program to 00000000000.
6
ADCS
ADC Start
Sets ADC Start mode.
0 = ADC normal operation
1 = Start ADC conversion process
Sets ADC mode.
000 = Disabled
001 = Temperature sensor
010 = Reserved
011 = Reserved
100 = Tune pin
101 = Reserved
110 = Reserved
111 = Reserved
5:3
ADCM[2:0]
ADC Mode
2:0
ADDR[2:0]
Register Address
www.maximintegrated.com
DEFINITION
Sets integer mode for F = 0.
0 = If F[11:0] = 0, then fractional-N mode is set
1 = If F[11:0] = 0, then integer-N mode is auto set
Sets lock-detect pin function.
00 = Low
01 = Digital lock detect
10 = Analog lock detect
11 = High
Control Register address bits, 101
Maxim Integrated │ 24
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Table 9. Register 6 (Address: 110, Read-Only Register)
BIT LOCATION
BIT ID
NAME
31:28
DIE[3:0]
Die ID
27:24
Reserved
Reserved
DEFINITION
Die ID.
0110 = MAX2870
0111 = MAX2871
Reserved.
Power-On-Reset
0 = Power has not been cycled since last read
1 = Power has not been cycled since last read. All registers have been
reset to default values.
23
POR
Power On Reset
22:16
ADC[6:0]
ADC Code
ADC Code.
15
ADCV
ADC Valid
Determines ADC code validity.
0 = Invalid ADC code
1 = Valid ADC code
14:10
Reserved
Reserved
Reserved.
9
VASA
VAS Active
Determines if VAS is Active.
0 = VCO Autoselect complete
1 = VCO Autoselect searching for correct VCO
8:3
V[5:0]
Current VCO
2:0
ADDR[2:0]
Register Address
www.maximintegrated.com
Current VCO.
Control Register address bits, 110
Maxim Integrated │ 25
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Typical Application Circuit
24
LD
TO GPIO
FROM GPIO
RFOUT_EN
GND_DIG
VCC_DIG
VCC_DIG
REF_IN
MUX
GND_SD
23
22
21
20
19
VCC_VCO
GND_VCO
NOISE_FILT
TUNE
GND_TUNE
RSET
REG
BIAS_FILT
VCC_RF
18
VCC_RF
17
25
16
26
15
27
14
28
13
MAX2871
29
12
30
11
EP
31
10
VCC_RF
RFOUTB_N
RFOUTB
RFOUTB_P
RFOUTA_N
RFOUTA
RFOUTA_P
GND_RF
VCC_PLL
VCC_PLL
VCC_DIG
VDD_SD
9
32
GND_PLL
VCC_RF
8
GND_CP
7
CP_OUT
6
VCC_CP
5
SW
4
CE
3
LE
2
DATA
CLK
1
VCC_PLL
R3
FROM
GPIO
SPI
INTERFACE
FOR BEST PERFORMANCE GENERATE
THREE SUPPLIES USING SEPARATE LDOS
VCC_RF
VCC_DIG
VCC_PLL
C1
C2
C3
R2A
R2B
www.maximintegrated.com
Maxim Integrated │ 26
MAX2871
Applications Information
VCO Manual Selection Operation
VCO manual selection operation (VAS_SHDN = 1) allows
shorter lock time, typically 200µS saving. It is also required
that multiple MAX2871 devices phase synchronization.
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
REFERENCE
REF_IN1
SYNC PULSE
MUX 1
MAX2871
The following steps need to be implemented:
1. Building VCO lookup table (Required ONLY once after
each power cycle)
● Set VAS_SHDN = 0, follow “VCO Autoselect (VAS)
State Machine” section to set BS bits properly
REF_IN2
MUX 2
● Write proper N and Frac value to Reg 0, triggering
MAX2871 to first desired frequency point, i.e freq1.
Wait for PLL to lock
MAX2871
● Read back register 6[8:3] from MUX pin and save
the value to memory as vco1, see detail at 4-Wire
Serial Interface section about register readback
REF_IN3
● Repeat above steps for all desired frequency points
MUX 3
2. VCO manual selection normal operation
● Set VAS_SHDN = 1
MAX2871
● Based on the VCO lookup table obtained from
step 1, write desired frequency’s corresponding
VCO value to reg3[31:26]
● Write proper N and Frac value to reg0, triggering
MAX2871 to desired frequency
Figure 5. Phase Synchronization Application Setup
Phase synchronization of multiple
MAX2871 devices
REF 1
Multiple MAX2871 devices can be phase synchronized.
This feature works in the frequency range of 187.5MHz to
6000 MHz and in Fractional-N mode ONLY.
REF 2
Proper hardware/register guidelines MUST be followed:
Hardware Design Guidelines
1. Connect all MAX2871 to same reference source.
Refer, Figure 5
REF 3
2. Connect MUX pins of all MAX2871 to 4 wire interface’s
readback
3. Connect MUX pins of all MAX2871 to same sync pulse
source
4. The relative delay of reference signal at each
MAX2871s reference pin can NOT be random. Refer
Figure 6.
www.maximintegrated.com
DELAY 12 AND DELAY 13 CAN
NOT BE RANDOM
DELAY 12
DELAY 13
Figure 6. Reference Signal Relative Delay
Maxim Integrated │ 27
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
5. At each MAX2871 REF_IN pin and MUX pin, the sync
rising edge can NOT occur inside the setup hold time
window around reference signal rising edge. Refer to
Figure 7.
tSETUP = (4/N) x tPFD + 2.6nS
tHOLD = (4/N) x tPFD
where: N is MAX2871’s N counter ratio, reg0[30:15]
tPFD = 1/(PFD frequency)
REF CLOCK AT REF_IN PIN
SYNC PULSE AT MUX PIN
Register Design Guidelines
1. The reference doubler and reference divide-by-2 must
be disabled.
DBR (reg2[25]) = 0
RDIV2 (reg2[24]) = 0
SYNC RISING EDGE NOT
INSIDE SETUP/HOLD TIME
WINDOW
2. R divider ratio must be set to 1
R (register 2, bits 23:14) = 1.
3. Set MAX2871 in Fractional mode
INT (reg0[31]) = 0
F01 (reg5[24]) = 0
HOLD TIME
4. Output divider has to be inside the PLL loop
FBMUX (reg4[23]) =0.
5. If OUTPUT B is used, it has to be set to “VCO divided
output” mode
BDIV (reg4[ 9]) = 0
6. Sigma delta modulator has to be in low noise mode
SDN (reg2[30:29]) = 00.
7. N counter ratio has to be in allowable range
19 < N (reg0[30:15]) < 4091
8. DIVA (register 4, bits 22:20) ≤ 100_binary (less than or
equal to divide-by-16, which limits the minimum output
frequency to 187.5MHz)
9. Set VAS_SHDN = 1, for normal operation
Steps to Execute Phase Sync
1. Follow “VCO Manual Selection Operation” section to
build VCO lookup table for each MAX2871 devices in
the system, only required once after each power cycle
2. Force the voltage on the MUX pin to VIL
3. Set MUX (reg5[18] & reg2[28:26]) = 0111 which allows
MUX to take external ‘SYNC INPUT’
4. Program the MAX2871s for the desired frequency and
allow them to lock. Ensure to use “VCO Manual selection Operation”
www.maximintegrated.com
SETUP TIME
Figure 7. Setup Time/ Hold Time Window
5. Force the voltage on the MUX pins to VIH. This resets
the MAX2871s so they are synchronous. The MUX
sync pulse rising edge cannot occur inside setup/hold
time window around the reference signal rising edge.
6. (Optional) If the user plans to use MUX pin’s other
function (i.e., register readback, follow steps below):
a. Force the voltage on the MUX pins back to VIL
b. Set MUX (reg5[18] and reg2[28:26]) = 0000
(HiZ mode)
c. Remove the forced voltage from the MUX pin
d. Now the MUX pin is ready for other functions
7. Set ONLY P(reg1[26:15]) for the desired amount of
phase shift for each part.
8. Set CDM (reg3[16:15]) = 10
9. Reset CDM (reg3[16:15]) = 00. All MAX2871s are
frequency synchronized with phase difference defined
in step 7. The initial phase sync is completed
10. Repeat step 2-10 for new frequency points
Maxim Integrated │ 28
MAX2871
Layout Issues
The MAX2871 EV kit can be used as a starting point for
layout. For best performance, take into consideration
grounding and routing of RF, baseband, and power supply PCB proper line. Make connections from vias to the
ground plane as short as possible. On the high impedance ports, keep traces short to minimize shunt capacitance. EV kit Gerber files can be requested/ downloaded
at www.maximintegrated.com.
Power-Supply Layout
To minimize coupling between different sections of the
IC, a star power-supply routing configuration with a large
decoupling capacitor at a central VCC_ node is recommended. The VCC_ traces branch out from this node,
each going to a separate VCC_ node in the circuit. Place
a bypass capacitor as close as possible to each supply
pin This arrangement provides local decoupling at each
VCC_ pin. Use at least one via per bypass capacitor for
a low-inductance ground connection. Do not share the
capacitor ground vias with any other branch.
www.maximintegrated.com
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX2871ETJ+
-40°C to +85°C
32 TQFN-EP*
+Denotes lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
32 TQFN-EP
T3255+5
21-0140
90-0013
Maxim Integrated │ 29
MAX2871
23.5MHz to 6000MHz Fractional/
Integer-N Synthesizer /VCO
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
9/14
Initial release
1
4/15
Updated Phase Adjustment section and other minor updates to data sheet
2
5/16
Updated Phase Adjustment section, Register 6 readout timing, other
general updates
3, 5, 11–13, 15, 18,
19, 21, 22, 24,
3
4/17
Added VCO Manual Selection and Phase Sync sections, as well as other
general updates/corrections
1–4, 11, 13–19, 21,
22, 24, 25, 27
4
6/20
Updated Detailed Description section
DESCRIPTION
—
1, 13, 17, 19, 24
13
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
© 2020 Maxim Integrated Products, Inc. │ 30
Mouser Electronics
Authorized Distributor
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