FeaTures
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LTC6947
Ultralow Noise 0.35GHz to
6GHz Fractional-N Synthesizer
DescripTion
The
LTC
®
6947
is a high performance, low noise, 6GHz
phase-locked loop (PLL), including a reference divider,
phase-frequency detector (PFD), ultralow noise charge
pump, fractional feedback divider, and VCO output divider.
The fractional divider uses an advanced, 4th order Δ∑
modulator which provides exceptionally low spurious
levels. This allows wide loop bandwidths, producing
extremely low integrated phase noise values.
The programmable VCO output divider, with a range of 1
through 6, extends the output frequency range. The dif-
ferential, low-noise output buffer has user-programmable
output power ranging from –4.3dBm to +4.5dBm, and may
be muted through either a digital input pin or software.
The ultralow noise charge pump contains selectable high
and low voltage clamps useful for VCO monitoring, and
also may be set to provide a V
+
/2 bias.
All device settings are controlled through a SPI-compatible
serial port.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
FracNWizard is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
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Low Noise Fractional-N PLL
No ∆Σ Modulator Spurs
18-Bit Fractional Denominator
350MHz to 6GHz VCO Input Range
–226dBc/Hz Normalized In-Band Phase Noise Floor
–274dBc/Hz Normalized In-Band 1/f Noise
–157dBc/Hz Wideband Output Phase Noise Floor
Excellent Integer Boundary Spurious Performance
Output Divider (1 to 6, 50% Duty Cycle)
Output Buffer Muting
Charge Pump Supply from 3.15V to 5.25V
Charge Pump Current from 1mA to 11.2mA
Reference Input Frequency Up to 425MHz
Fast Frequency Switching
FracNWizard™ Software Design Tool Support
applicaTions
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Wireless Basestations (LTE, WiMAX, W-CDMA, PCS)
Broadband Wireless Access
Microwave Data Links
Military and Secure Radio
Test and Measurement
Typical applicaTion
11GHz Source for Satellite Communications
10nF
0.1µF
1µF
1µF
GND
REF
–
V
CP+
V
REF+
GND
V
VCO+
REF
+
STAT
CS
SCLK
SDI
SDO
LDO
V
D+
CP
GND
GND
GND
GND
GND
GND
VCO
+
VCO
–
1µF
3.3V
5V
0.01µF
3.3V
0.01µF
3.3nF
0.1µF 5V
60.4
220nF
60.4
5V
4.99k
4.99k
13V
+
0.1µF
47µF
+
–
LT1678IS8
OUT
10nF
0.1µF
System Phase Noise,
f
RF
= 11.260GHz
–80
–90
–100
PHASE NOISE (dBc/Hz)
–110
–120
–130
–140
RMS NOISE = 0.549°
–150 RMS JITTER = 135fs
–160 f
PFD
= 50MHz
LOOP BW = 34kHz
–170 INTN = 0
CPLE = 1
–180
100
1k
10k 100k
1M
10M
OFFSET FREQUENCY (Hz)
100MHz
51.1
SPI BUS
0.1µF
LTC6947IUFD
100pF
f
LO
/2
VTUNE
MA-COM
MAOC-009266
47nF
75
1nF
MUTE
V
RF+
GND
RF
–
RF
+
3.3V
3.3V
0.1µF
3.3V
BB
100pF
100M
68nH
3.3V
0.01µF
f
LO
= 10.2GHz TO 11.3GHz IN 381.4Hz STEPS
R = 2, f
PFD
= 50MHz
N = 102 TO 113
LBW = 33.6kHz
6947 TA01a
6946 TA01b
0.01µF
68nH 100pF
100pF
AUXILIARY OUTPUTS
f
LO
/2, /4, /6, /8, /10 OR /12
6947f
For more information
www.linear.com/LTC6947
1
LTC6947
absoluTe MaxiMuM raTings
(Note 1)
pin conFiguraTion
TOP VIEW
V
VCO+
22 GND
21 GND
20 GND
29
GND
19 GND
18 GND
17 GND
16 VCO
+
15 VCO
–
9 10 11 12 13 14
MUTE
V
RF+
GND
RF
–
RF
BB
+
Supply Voltages
V
+
(V
REF+
, V
RF+
, V
VCO+
, V
D+
) to GND ...................3.6V
V
CP+
to GND.........................................................5.5V
Voltage on CP Pin .................GND – 0.3V to V
CP+
+ 0.3V
Voltage on all other Pins ...........GND – 0.3V to V
+
+ 0.3V
Operating Junction Temperature Range, T
J
LTC6947I (Note 2) ............................. –40°C to 105°C
Junction Temperature, T
JMAX
................................ 125°C
Storage Temperature Range .................. –65°C to 150°C
V
REF+
REF
–
V
CP+
28 27 26 25 24 23
REF
+
1
STAT 2
CS
3
SCLK 4
SDI 5
SDO 6
LDO 7
V
D+
8
UFD PACKAGE
28-LEAD (4mm
×
5mm) PLASTIC QFN
T
JMAX
= 125°C,
θ
JCbottom
= 7°C/W
EXPOSED PAD (PIN 29) IS GND, MUST BE SOLDERED TO PCB
orDer inForMaTion
LEAD FREE FINISH
LTC6947IUFD#PBF
TAPE AND REEL
LTC6947IUFD#TRPBF
PART MARKING
6947
PACKAGE DESCRIPTION
JUNCTION TEMPERATURE RANGE
28-Lead (4mm
×
5mm) Plastic QFN –40°C to 105°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
REF+
= V
D+
= V
RF+
= V
VCO+
= 3.3V, V
CP+
= 5V unless otherwise
specified (Note 2). All voltages are with respect to GND.
SYMBOL
f
REF
V
REF
PARAMETER
Input Frequency
Input Signal Level
Input Slew Rate
Input Duty Cycle
Self-Bias Voltage
Input Resistance
Input Capacitance
Differential
Differential
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elecTrical characTerisTics
CONDITIONS
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MIN
10
0.5
20
GND
CP
TYP
MAX
425
UNITS
MHz
V
P-P
V/µs
%
Reference Inputs (REF
+
, REF
–
)
Single-Ended, 1µF AC-Coupling Capacitors
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2
50
2.7
1.65
5.8
1.85
8.4
14
2.25
11.6
V
kΩ
pF
6947f
2
For more information
www.linear.com/LTC6947
LTC6947
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
REF+
= V
D+
= V
RF+
= V
VCO+
= 3.3V, V
CP+
= 5V unless otherwise
specified (Note 2). All voltages are with respect to GND.
SYMBOL
f
VCO
P
VCOI
PARAMETER
Input Frequency
Input Power Level
Input Resistance
RF Output (RF
+
, RF
–
)
f
RF
O
Output Frequency
Output Divider Range
Output Duty Cycle
Output Resistance
P
RF-SE
Output Power, Single-Ended, f
RF
= 900MHz
Single-Ended, Each Output to V
RF+
RFO[1:0] = 0, R
Z
= 50Ω, LC Match
RFO[1:0] = 1, R
Z
= 50Ω, LC Match
RFO[1:0] = 2, R
Z
= 50Ω, LC Match
RFO[1:0] = 3, R
Z
= 50Ω, LC Match
R
Z
= 50Ω, Single-Ended, O = 2 to 6
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elecTrical characTerisTics
CONDITIONS
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MIN
350
–8
94
350
1
TYP
MAX
6000
UNITS
MHz
dBm
Ω
MHz
%
VCO Input (VCO
+
, VCO
–
)
R
Z
= 50Ω, Single-Ended
Single-Ended, Each Input
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0
132
6
161
6000
6
All Integers Included
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50
100
–9
–6.1
–2.9
0.1
136
–7.3
–4.5
–1.4
1.5
175
–5.5
–2.8
0.2
3.0
–80
110
170
100
76.1
66.3
56.1
45.9
34.3
1
11.2
±6
±3.5
±2
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Ω
dBm
dBm
dBm
dBm
dBm
ns
ns
MHz
MHz
MHz
MHz
MHz
MHz
mA
%
%
%
%/V
ppm/°C
nA
V
V
V/V
Output Power, Muted, f
RF
= 900MHz
Mute Enable Time
Mute Disable Time
Phase/Frequency Detector
f
PFD
Input Frequency
Integer mode
Fractional mode
LDOEN = 0
LDOV = 3, LDOEN = 1
LDOV = 2, LDOEN = 1
LDOV = 1, LDOEN = 1
LDOV = 0, LDOEN = 1
8 Settings (See Table 6)
All Settings, V(CP) = V
CP+
/2
I
CP
= 1.0mA to 2.8mA, V(CP) = V
CP+
/2
I
CP
= 4.0mA to 11.2mA, V(CP) = V
CP+
/2
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Charge Pump
I
CP
Output Current Range
Output Current Source/Sink Accuracy
Output Current Source/Sink Matching
Output Current vs Output Voltage Sensitivity (Note 3)
Output Current vs Temperature
Output Hi-Z Leakage Current
V
CLMP-LO
V
CLMP-HI
V
MID
R
N
Low Clamp Voltage
High Clamp Voltage
Mid-Supply Output Bias Ratio
Divide Range
Divide Range
V(CP) = V
CP+
/2
I
CP
= 11.2mA, CPCLO = CPCHI = 0 (Note 3)
CPCLO = 1
CPCHI = 1, Referred to V
CP+
Referred to (V
CP+
– GND)
All Integers Included
All Integers Included, Integer Mode
All Integers Included, Fractional Mode
All Integers Included
0.2
170
0.03
0.84
–0.96
0.48
1.0
Reference (R) Divider
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1
32
35
1
31
1023
1019
262143
Counts
Counts
Counts
Counts
VCO (N) Divider
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Fractional ∆∑ Modulator
Numerator Range
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6947f
For more information
www.linear.com/LTC6947
3
LTC6947
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
REF+
= V
D+
= V
RF+
= V
VCO+
= 3.3V, V
CP+
= 5V unless otherwise
specified (Note 2). All voltages are with respect to GND.
SYMBOL
Modulator LDO
Output Voltage
External Pin Capacitance
Digital Pin Specifications
V
IH
V
IL
V
IHYS
I
OH
I
OL
High Level Input Voltage
Low Level Input Voltage
Input Voltage Hysteresis
Input Current
High Level Output Current
Low Level Output Current
SDO Hi-Z Current
Digital Timing Specifications (See Figure 7 and Figure 8)
t
CKH
t
CKL
t
CSS
t
CSH
t
CS
t
CH
t
DO
SCLK High Time
SCLK Low Time
CS
Setup Time
CS
High Time
SDI to SCLK Setup Time
SDI to SCLK Hold Time
SCLK to SDO Time
V
REF+
Supply Range
V
D+
Supply Range
V
RF+
Supply Range
V
VCO+
Supply Range
V
CP+
Supply Range
Power Supply Currents
I
DD
I
CC(5V)
I
CC(3.3V)
V
D+
Supply Current
Sum V
CP+
Supply Currents
Sum V
REF+
, V
RF+
, V
VCO+
Supply Currents
Digital Inputs at Supply Levels, PDFN = 1
Digital Inputs at Supply Levels, Fractional
Mode, f
PFD
= 66.3MHz MHz, LDOV[1:0] = 3
I
CP
= 11.2mA
I
CP
= 1.0mA
PDALL = 1
RF Muted, OD[2:0] = 1
RF Enabled, RFO[1:0] = 0, OD[2:0] = 1
RF Enabled, RFO[1:0] = 3, OD[2:0] = 1
RF Enabled, RFO[1:0] = 3, OD[2:0] = 2
RF Enabled, RFO[1:0] = 3, OD[2:0] = 3
RF Enabled, RFO[1:0] = 3, OD[2:0] = 4 to 6
PDALL = 1
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elecTrical characTerisTics
PARAMETER
CONDITIONS
LDO Enabled, Four Values
LDO Disabled
Required for LDO Stability
MUTE, CS,
SDI, SCLK
MUTE, CS,
SDI, SCLK
MUTE, CS,
SDI, SCLK
MUTE, CS,
SDI, SCLK
SDO and STAT, V
OH
= V
D+
– 400mV
SDO and STAT, V
OL
= 400mV
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MIN
TYP
1.7 to 2.6
V
D+
MAX
UNITS
V
V
0.047
1.55
0.1
1
µF
V
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0.8
250
±1
–3.3
2.0
3.4
±1
25
25
10
10
6
6
16
3.15
3.15
3.15
3.15
3.15
3.3
3.3
3.3
3.3
3.45
3.45
3.45
3.45
5.25
1500
22
40
14
650
80
95
105
125
135
140
250
–1.9
V
mV
µA
mA
mA
µA
ns
ns
ns
ns
ns
ns
ns
V
V
V
V
V
µA
mA
mA
mA
µA
mA
mA
mA
mA
mA
mA
µA
To V
IH
/V
IL
/Hi-Z with 30pF Load
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Power Supply Voltages
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18.2
34
12
230
70.4
81.1
91.3
109.2
114.8
119.6
53
6947f
4
For more information
www.linear.com/LTC6947
LTC6947
The
l
denotes the specifications which apply over the full operating
junction temperature range, otherwise specifications are at T
A
= 25°C. V
REF+
= V
D+
= V
RF+
= V
VCO+
= 3.3V, V
CP+
= 5V unless otherwise
specified (Note 2). All voltages are with respect to GND.
SYMBOL
L
MIN
PARAMETER
Output Phase Noise Floor (Note 5)
CONDITIONS
RFO[1:0] = 3, OD[2:0] = 1, f
RF
= 6GHz
RFO[1:0] = 3, OD[2:0] = 2, f
RF
= 3GHz
RFO[1:0] = 3, OD[2:0] = 3, f
RF
= 2GHz
RFO[1:0] = 3, OD[2:0] = 4, f
RF
= 1.5GHz
RFO[1:0] = 3, OD[2:0] = 5, f
RF
= 1.2GHz
RFO[1:0] = 3, OD[2:0] = 6, f
RF
= 1.0GHz
L
NORM(INT)
L
NORM(FRAC)
L
1/f
Integer Normalized In-Band Phase Noise
Floor
Fractional Normalized In-Band Phase Noise
Floor
Normalized In-Band 1/f Phase Noise
In-Band Phase Noise Floor
Integrated Phase Noise from 100Hz to
40MHz
Spurious
INTN = 1, I
CP
= 5.6mA (Notes 6, 7, 9)
INTN = 0, CPLE = 1, I
CP
= 5.6mA
(Notes 6, 7, 9)
I
CP
= 11.2mA (Notes 6, 10)
Fractional Mode, CPLE = 1
(Notes 4, 6, 7, 10, 11)
Fractional Mode, CPLE = 1 (Notes 4, 7, 11)
Fractional Mode, f
OFFSET
= f
PFD
, PLL Locked
(Notes 4, 7, 11, 12)
MIN
TYP
–155
–155
–156
–156
–157
–158
–226
–225
–274
–109
0.076
–97
MAX
UNITS
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
dBc/Hz
°RMS
dBc
Phase Noise and Spurious
elecTrical characTerisTics
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC6947I is guaranteed to meet specified performance limits
over the full operating junction temperature range of –40°C to 105°C.
Note 3:
For 0.9V < V(CP) < (V
CP+
– 0.9V).
Note 4:
VCO is Crystek CVCO55C-2328-2536.
Note 5:
f
VCO
= 6GHz, f
OFFSET
= 40MHz.
Note 6:
Measured inside the loop bandwidth with the loop locked.
Note 7:
Reference frequency supplied by Wenzel 501-04516, f
REF
=
100MHz, P
REF
= 10dBm.
Note 8:
Reference frequency supplied by Wenzel 500-23571, f
REF
=
61.44MHz, P
REF
= 10dBm.
Note 9:
Output phase noise floor is calculated from normalized phase
noise floor by L
OUT
= L
NORM
+ 10log
10
(f
PFD
) + 20log
10
(f
RF
/f
PFD
).
Note 10:
Output 1/f noise is calculated from normalized 1/f phase noise by
L
OUT(1/f)
= L
1/f
+ 20log
10
(f
RF
) – 10log
10
(f
OFFSET
).
Note 11:
I
CP
= 5.6mA, f
PFD
= 50MHz, FILT[1:0] = 0, Loop BW = 31kHz;
f
RF
= 2415MHz, f
VCO
= 2415MHz.
Note 12:
Measured using DC1846.
Note 13:
VCO is RFMD UMX-918-D16-G.
6947f
For more information
www.linear.com/LTC6947
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