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dc1795af

DEMO MANUAL DC1795A

Description

LTC6950

1.4GHz Low Phase Noise, Low Jitter PLL

with Clock Distribution

Demonstration circuit 1795A features the LTC®6950, a

1.4GHz low phase noise, low jitter PLL with clock dis-

tribution.

For ease of use, the DC1795A comes installed with a

100MHz reference and a 1GHz VCSO, voltage controlled

SAW oscillator with sine wave output. All differential

inputs and outputs have 0.5" spaced SMA connectors.

The DC1795A has four AC coupled LVPECL outputs with

50Ω transmission lines making them suitable to drive

50Ω impedance instruments. The LVDS/CMOS output is

DC coupled. The LTC6950’s EZSync™ function is made

available via a turret and an SMA connector.

L

, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and EZSync

and ClockWizard are trademarks of Linear Technology Corporation. All other trademarks are the

property of their respective owners.

For the evaluation of the LTC6950 with other VCOs and

references,theDC1795Acanbemodifiedtoaccommodate

different on-board or external components. It also allows

the user the option of a passive or active loop filter.

A DC590 USB serial controller board is used for SPI com-

munication with the LTC6950, controlled by the supplied

ClockWizard™ software.

Design files for this circuit board are available at

http://www.linear.com/demo/DC1795A

Figure 1. DC1795A Connections

Ribbon

cable

connection

to DC590

LVDS/CMOS

DC-coupled

Outputs, SMA

PECL0

AC Coupled

Outputs, SMA

Frequency Reference

Input, SMA

PECL1

AC Coupled

Outputs, SMA

PECL2

AC Coupled

Outputs, SMA

PECL3

AC Coupled

Outputs, SMA

5V DC Supply,

BNC & turret

3.3V DC Supply,

BNC & turret

5V U4 (VCXO) DC

Supply, turret

U3 (VCO) DC

Supply, turret

External VCO

Input, SMA

External VCO Charge

Pump Output, SMA

and turret

Active Loop Filter

Op-amp (U2) DC

Supply, turret

SYNC Input,

SMA & turret

Stat Outputs,

turrets