LTC6947
Ultralow Noise 0.35GHz to
6GHz Fractional-N Synthesizer
FeaTures
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,fractionalfeedbackdivider,andVCOoutputdivider.
n
Low Noise Fractional-N PLL
n
No ∆Σ Modulator Spurs
n
18-Bit Fractional Denominator
n 350MHz to 6GHz VCO Input Range
n
–226dBc/Hz Normalized In-Band Phase Noise Floor
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.
n
–274dBc/Hz Normalized In-Band 1/f Noise
n
–157dBc/Hz Wideband Output Phase Noise Floor
n
Excellent Integer Boundary Spurious Performance
n
Output Divider (1 to 6, 50% Duty Cycle)
Output Buffer Muting
n
n
n
n
n
n
The programmable VCO output divider, with a range of 1
through 6, extends the output frequency range. The dif-
ferential, low-noise outputbuffer has user-programmable
outputpowerrangingfrom–4.3dBmto+4.5dBm,andmay
be muted through either a digital input pin or software.
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
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.
+
applicaTions
n
AlldevicesettingsarecontrolledthroughaSPI-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.
Wireless Basestations (LTE, WiMAX, W-CDMA, PCS)
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Broadband Wireless Access
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Microwave Data Links
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Military and Secure Radio
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Test and Measurement
Typical applicaTion
11GHz Source for Satellite Communications
13V
4.99k
System Phase Noise,
fRF = 11.260GHz
10nF
5V
60.4Ω
47µF
+
4.99k
0.1µF
+
–
LT1678IS8
OUT
3.3V
5V
0.1µF
0.1µF
–80
–90
0.01µF
1µF
3.3V
–100
–110
–120
–130
–140
–150
–160
10nF
0.01µF
1µF
100MHz
51.1Ω
+
3.3nF
REF
GND
GND
GND
220nF
STAT
CS
SCLK
SDI
SDO
LDO
+
60.4Ω
5V
0.1µF
GND
GND
GND
RMS NOISE = 0.549°
RMS JITTER = 135fs
PFD
LOOP BW = 34kHz
SPI BUS
LTC6947IUFD
100pF
75Ω
1nF
f
= 50MHz
47nF
f
/2
VTUNE
MA-COM
LO
+
0.1µF
VCO
–170 INTN = 0
3.3V
–
V
D
VCO
CPLE = 1
3.3V
–180
MAOC-009266
100pF
100
1k
10k 100k
1M
10M 100M
0.1µF
OFFSET FREQUENCY (Hz)
3.3V
1µF
3.3V
6946 TA01b
68nH
f
= 10.2GHz TO 11.3GHz IN 381.4Hz STEPS
LO
0.01µF
R = 2, f
N = 102 TO 113
LBW = 33.6kHz
= 50MHz
68nH
PFD
0.01µF
100pF
100pF
AUXILIARY OUTPUTS
f
LO
/2, /4, /6, /8, /10 OR /12
6947 TA01a
6947f
1
For more information www.linear.com/LTC6947