LTC6945_15 Datasheet, PDF (1/28 Pages) Linear Technology – Ultralow Noise and Spurious 0.35GHz to 6GHz Integer-N Synthesizer

LTC6945
Ultralow Noise and Spurious
0.35GHz to 6GHz Integer-N
Synthesizer
Features
Description
nn _{Low Noise Integer-N PLL}
nn _{350MHz to 6GHz VCO Input Range}
nn _{–226dBc/Hz Normalized In-Band Phase Noise Floor}
nn _{–274dBc/Hz Normalized In-Band 1/f Noise}
nn _{–157dBc/Hz Wideband Output Phase Noise Floor}
nn _{Excellent Spurious Performance}
nn _{Output Divider (1 to 6, 50% Duty Cycle)}
nn _{Low Noise Reference Buffer}
nn _{Output Buffer Muting}
nn _{Charge Pump Supply from 3.15V to 5.25V}
nn _{Charge Pump Current from 250µA to 11.2mA}
nn _{Configurable Status Output}
nn _{SPI Compatible Serial Port Control}
nn _{PLLWizard™ Software Design Tool Support}
Applications
The LTC^®6945 is a high performance, low noise, 6GHz phase-
locked loop (PLL), including a reference divider, phase-
frequency detector (PFD) with phase-lock indicator, charge
pump, integer feedback divider and VCO output divider.
The part features a buffered, programmable VCO output
divider with a range of 1 through 6. The differential, low
noise output buffer has user-programmable output power
ranging from –6dBm to 3dBm, and may be muted through
either a digital input pin or software.
The low noise reference buffer outputs a typical 0dBm
square wave directly into a 50Ω impedance from 10MHz
to 250MHz, or may be disabled through 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.
nn _{Wireless Base Stations (LTE, WiMAX, W-CDMA, PCS)}
nn _{Broadband Wireless Access}
nn _{Microwave Data Links}
nn _{Military and Secure Radio}
nn _{Test and Measurement}
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
PLLWizard is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
Typical Application
LTC6945 Data Converter Sample Clock
3.3V LOOP
0.1µF
BANDWIDTH
~2.3kHz
V_TUNE
5V _CRYSTEK
CVCSO-914-1000
100MHz ^51.1Ω
5V
0.1µF ^432Ω
47nF
REF
1µF
570nF
1µF
3.3V
0.1µF
SPI BUS
3.3V
0.1µF
REF^– REF⁺ V_REF+ CP V_CP+ GND
V_REFO+
V_VCO+
REFO
GND
LTC6945
STAT
GND
CS
GND
SCLK
GND
GND
SDI
GND
SDO
f_PFD = 25MHz ^VCO+
V_D+
V_CO–
MUTE GND RF^– RF⁺ V_RF+ BB
3.3V 0.01µF
16.5Ω
100pF
1.0µF
100pF
16.5Ω
16.5Ω
100pF
68nH
3.3V
100pF
50Ω
3.3V 0.01µF
68nH
3.3V
100pF
ALT SAMPLE CLOCK
500MHz OR 1GHz
SAMPLE CLOCK
1GHz, 7dBm
6945 TA01b
1GHz Sample Clock Phase Noise
–100
–110
–120
–130
–140
–150
–160
–170
–180
100
DSB INTEGRATION
(100Hz TO 1GHz)
RMS NOISE = 0.014°
RMS JITTER = 39fs
f_PFD = 25MHz
BW = 2.3kHz
1k 10k 100k 1M
OFFSET FREQUENCY (Hz)
10M 40M
6945 TA01b
For more information www.linear.com/LTC6945
6945fa
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