Datasheet

/125
Phase
Frequency
Detector
Charge
Pump
M divider
/128
N divider
/48
Feedback
Divider (FB)
Loop Filter
VCO
/4
Output
Divider (P)
20MHz
983.04MHz
245.76MHz
U0 (LVCMOS)
U1 (LVPECL)
3mA
160kHz
CDCE72010
¦
OUT
=
¦
VCO
P
¦ ¦
IN VCO
M
(FBxN)
£
100MHz
£
¦
OUT
1.5GHz
£
¦
IN
500MHz
£
¦
VCO
1.5GHz
=
(
(
160kHz
2.2.2.3 Clock Option 3
2.2.3 Analog Inputs
www.ti.com Circuit Description
Y0 pin of CDCE72010 is 245.76 MHz. This clock is filtered using the crystal filter with center frequency of
245.76 MHz. By default, the VCXO and the crystal filter are not populated on the EVM, so that the user
can populate the components depending on the end application and sampling rate. This configuration is
recommended for applications requiring an onboard clock generation scheme. The test result using this
option is shown in Figure 8 .
Figure 4. CDCE72010 EEPROM Configuration Block Diagram
Option 3 is used for a differential LVPECL clock. This configuration eliminates the need for a crystal filter.
It uses the same EEPROM configuration as Option 2, but in this case, the ADC clock pins are connected
to Y1N and Y1P. The jumper setting uses the clock output Y1P and Y1N from CDCE72010, to clock ADC.
This configuration is not recommended for SNR critical applications. Notice that the clock frequency does
not change. The frequency remains the same as in Clock Option 2. The test result using this option is
shown in Figure 9 .
The EVM can be configured to use either a transformer-coupled input or a TH4509 amplifier input, both
from a single-ended source. The SMA connector J6 provides the single-ended analog input to the
transformer-coupled input circuit to the ADC. The SMA connector J8 is not installed by default, but can be
used to bring a differential input clock to the transformer-coupled input or to bring a single-ended input to
the THS4509 input circuit. To set the transformer up for one of these options, the EVM must be configured
as per the options listed in Table 7 . See the schematic located at the end of this document prior to making
any jumper changes .
SLWU061A – December 2008 – Revised June 2009 ADS61x9/55xxEVM 13
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