LTC6945 查看數據表（PDF） - Linear Technology

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LTC6945

Ultralow Noise and Spurious 0.35GHz to 6GHz Integer-N Synthesizer

Linear Technology 

LTC6945

FEATURES

Ultralow Noise and Spurious

0.35GHz to 6GHz Integer-N

Synthesizer

DESCRIPTION

n Low Noise Integer-N PLL

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 Spurious Performance

n Output Divider (1 to 6, 50% Duty Cycle)

n Low Noise Reference Buffer

n Output Buffer Muting

n Charge Pump Supply from 3.15V to 5.25V

n Charge Pump Current from 250μA to 11.2mA

n Configurable Status Output

n SPI Compatible Serial Port Control

n PLLWizard™ Software Design Tool Support

APPLICATIONS

n Wireless Base Stations (LTE, WiMAX, W-CDMA, PCS)

n Broadband Wireless Access

n Microwave Data Links

n Military and Secure Radio

n Test and Measurement

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.

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

VTUNE

5V CRYSTEK

CVCSO-914-1000

100MHz 51.1Ω

REF

470pF

470pF

5V

432Ω

47nF

0.1μF

570nF

3.3V

0.1μF

SPI BUS

3.3V

0.1μF

REF– REF+

VREFO+

VREF+

CP

VCP+VGVNCOD+

REFO

GND

LTC6945

STAT

GND

CS

GND

GND

SCLK

GND

SDI

GND

SDO

fPFD = 25MHz VCO+

VD+

VCO–

MUTE GND RF– RF+ VRF+ 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

fPFD = 25MHz

BW = 2.3kHz

1k 10k 100k 1M

OFFSET FREQUENCY (Hz)

10M 40M

6945 TA01b

6945f

1

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