Evaluation Board Operation - Analog Devices AD9776 Instruction Manual

EVALUATION BOARD OPERATION

The AD977x evaluation board is designed to optimize the DAC
performance and the speed of the digital interface while
remaining user friendly. To operate the board, the user needs a
power source, a clock source, and a digital data source. The user
also needs a spectrum analyzer or an oscilloscope to look at the
DAC output. The diagram in Figure 98 illustrates the test setup.
A sine or square wave clock works well as a clock source. The dc
offset on the clock is not a problem, since the clock is ac-
coupled on the evaluation board before the DACCLK inputs.
All necessary connections to the evaluation board are shown in
more detail in Figure 99.
CLOCK
GENERATOR
ADAPTER
CABLES
CLKIN
DIGITAL
PATTERN
GENERATOR
CLOCK IN
DATACLK OUT
Figure 98. Typical Test Setup
AUX33 DVDD18
P4 Digital Input Connector
S7 DCLKOUT
Figure 99. AD977x Evaluation Board Showing all Connections
The evaluation board comes with software that allows the user
to program the SPI port. Via the SPI port, the devices can be
programmed into any of its various operating modes. When
first operating the evaluation board, it is useful to start with a
simple configuration, that is, a configuration in which the SPI
port settings are as close as possible to the default settings. The
default software window is shown in Figure 100. The arrows
indicate which settings need to be changed for an easy first time
evaluation. Note that this implies that the PLL is not being used
and that the clock being used is at the speed of the DAC output
sample rate. For a more detailed description of how to use the
PLL, see the PLL Loop Filter Bandwidth section.
SPI PORT
SPECTRUM
ANALYZER
AD9779
EVALUATION
BOARD
1.8V POWER SUPPLY
3.3V POWER SUPPLY
DVDD33 CVDD18 AVDD33
J1 CLOCK IN MODULATOR
JP4
S5 OUTPUT 1
JP15
JP8
JP14
AD8349
AD9779
JP3
JP16
JP2
S6 OUTPUT 2
JP17
ANALOG
DEVICES
AD9779/8/6
SPI PORT
Rev. 0 | Page 45 of 56
AD9776/AD9778/AD9779
J2
5V Supply
OUTPUT
+5V
GND
LOCAL OSC
INPUT
REV D