LTC6947_15 Datasheet, PDF (1/32 Pages) Linear Technology – Ultralow Noise 0.35GHz to 6GHz Fractional-N Synthesizer

LTC6947
Ultralow Noise 0.35GHz to
6GHz Fractional-N Synthesizer
Features
Description
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}
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)}
n _{Output Buffer Muting}
n _{Charge Pump Supply from 3.15V to 5.25V}
n _{Charge Pump Current from 1mA to 11.2mA}
n _{Reference Input Frequency Up to 425MHz}
n _{Fast Frequency Switching}
n _{FracNWizard™ Software Design Tool Support}
Applications
n _{Wireless Basestations (LTE, WiMAX, W-CDMA, PCS)}
n _{Broadband Wireless Access}
n _{Microwave Data Links}
n _{Military and Secure Radio}
n _{Test and Measurement}
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.
Typical Application
11GHz Source for Satellite Communications
0.1µF
10nF
3.3V
1µF
60.4Ω ^5V
5V
0.01µF
3.3V
1µF
100MHz
51.1Ω
SPI BUS
0.1µF
3.3V
3.3V
REF⁺
STAT
CS
SCLK
SDI
SDO
LDO
V_D+
LTC6947IUFD
GND
GND
GND
GND
GND
GND
VCO⁺
VCO^–
4.99k
4.99k _0.1µF
0.01µF
+ 47µF
13V
+
LT1678IS8
OUT
–
10nF
0.1µF ^5V
3.3nF
60.4Ω
220nF
100pF
f_LO/2
100pF
47nF
VTUNE
MA-COM
MAOC-009266
0.1µF
75Ω
1nF
0.1µF
3.3V _68nH
3.3V
1µF
f_LO = 10.2GHz TO 11.3GHz IN 381.4Hz STEPS
0.01µF
68nH _100pF
0.01µF
100pF
R = 2, f_PFD = 50MHz
N = 102 TO 113
LBW = 33.6kHz
AUXILIARY OUTPUTS
f_LO/2, /4, /6, /8, /10 OR /12
6947 TA01a
For more information www.linear.com/LTC6947
System Phase Noise,
f_RF = 11.260GHz
–80
–90
–100
–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 100M
OFFSET FREQUENCY (Hz)
6946 TA01b
6947f
1