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Signal Path and Control Circuitry
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Software Selectable Options
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Installing the GUI Interface and USB Driver
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Signal Path and Control Circuitry
The CDCE72010 provides support for selectable tri-inputs, and two of the inputs (PRI REF and SEC REF)
can accept a 8-kHz to 500-MHz frequency input from a differential signal source or a 8-kHz to 200-MHz
frequency input from a single-ended signal source.
The CDCE72010 provides support for up to ten differential (LVDS or LVPECL) or 20 single-ended
(LVCMOS) or any combination of outputs up to 1.5 GHz. On the CDCE72010EVM, output 1 and output 8
have a footprint option for installing crystal filters that can drive the phase noise floor down by 10 dB or 15
db. This filtered signal is intended to be used for clocking high-performance, high-speed analog-to-digital
converters (ADC).
The CDCE72010 requires an external loop filter. The loop filter selection determines the PLL loop stability
and also affects the phase noise of the output. The EVM provides four sets of filters optimized for a
30.72-MHz reference and 491.52-MHz VCXO. For any output of the CDCE72010, the frequency is
determined by the selection of the VCO/VCXO and the setting of the output divider. The output jitter
performance is determined by the PLL settings (including the PFD frequency, charge pump current, and
the loop filter). See the CDCE72010 data sheet for more details and configuration settings.
Each of the ten outputs of the CDCE72010 can be selected through the software interface as LVPECL,
LVDS, or LVCMOS. The CDCE72010EVM provides software selectable 150-
Ω
current-setting resistors.
The LVCMOS outputs work for frequencies up to 250 MHz; the LVDS outputs run up to 800 MHz; and
LVPECL outputs function up to 1.175 MHz (these are all minimum frequencies).
The provided GUI software allows users to easily send commands to the CDCE72010 through the
host-powered USB interface. The EVM includes a slave USB controller that transmits the commands to
the SPI programming interface included on the CDCE72010. The DC power for the USB controller can
either be derived from the 5-V power pin in the USB cable or by using an external 5-V DC adapter into the
slot available on the EVM. If the device is accessible for programming by the SPI programming interface
through the USB controller, the onboard LED D25 is illuminated on power up.
In addition to writing commands to the CDCE72010 RAM while the board is powered, commands also can
be stored in CDCE72010 EEPROM. This allows users to start the EVM in the desired state without
needing programming at power up.
Note that the CDCE72010 has a permanent EEPROM lock mode. After this mode is selected, the
EEPROM within the CDCE72010 cannot be changed. This is useful when setting final configurations.
The CDCE72010EVM software also provides support for the device GUI configurations to be saved into a
configuration file, which can be opened at a later time with this GUI.
To start installation, run the
CDCE72010 Control GUI v1.X.X.msi
file.
Make note of the installation folder because you may need to refer to it when the USB cable is connected
and asks for the location of a driver file.
After the setup wizard has completed, start the GUI interface from the start menu (Start
→
CDCE72010
Control GUI).
SLAU250 – May 2008
1.5-GHz Low-Phase Noise Clock Evaluation Board
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