AD9778_15 Datasheet, PDF (46/56 Pages) Analog Devices – Dual 12-/14-/16-Bit, 1 GSPS, Digital-to-Analog Converters

AD9776/AD9778/AD9779
EVALUATION BOARD OPERATION
The AD977x evaluation board is designed to optimize the DAC
performance and the speed of the digital interface, yet remains
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 100 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 REFCLK inputs. All
necessary connections to the evaluation board are shown in
more detail in Figure 101.
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 102. 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.
CLOCK
GENERATOR
ADAPTER
CABLES
CLKIN
SPI PORT
DIGITAL
PATTERN
GENERATOR
CLOCK IN
DATACLK OUT
AD9779
EVALUATION
BOARD
Figure 100. Typical Test Setup
SPECTRUM
ANALYZER
1.8V POWER SUPPLY
3.3V POWER SUPPLY
AUX33
DVDD18
DVDD33 CVDD18
AVDD33
J2
5V Supply
P4 Digital Input Connector
S7 DCLKOUT
J1 CLOCK IN
MODULATOR
JP4
OUTPUT
JP15
S5 OUTPUT 1
AD9779
JP8
JP14
JP3
JP16
AD8349
+5V
GND
JP2
JP17
S6 OUTPUT 2
LOCAL OSC
INPUT
ANALOG
DEVICES
SPI PORT
AD9779/8/6
REV D
Figure 101. AD977x Evaluation Board Showing All Connections
Rev. A | Page 46 of 56