AD9786-EB Analog Devices Inc, AD9786-EB Datasheet - Page 45

• Manufacturer Part Number: AD9786-EB
• Description: BOARD EVALUATION FOR AD9786
• Manufacturer: Analog Devices Inc
• Series: TxDAC+®r

Specifications of AD9786-EB

• Number Of Dac's: 1
• Number Of Bits: 16
• Outputs And Type: 1, Differential
• Sampling Rate (per Second): 500M
• Data Interface: Parallel
• Dac Type: Current
• Voltage Supply Source: Single
• Operating Temperature: -40°C ~ 85°C
• Utilized Ic / Part: AD9786
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DATA INPUTS
Digital data inputs to the AD9786 are accessed on the evaluation
board through Connector J1 and Connector J2. These are 40-pin,
right-angle connectors that are intended to be used with standard
ribbon cable connectors. The input level should be 3.3 V. The
data format is selectable through Register 0x02, Bit 7 (DATAFMT).
With this bit set to a default 0, the AD9786 assumes that the input
data is in twos complement format. With this bit set to 1, data
should be input in offset binary format.
When the evaluation board is first powered up and the clock
and data are running, it is recommended that the proper operating
current be verified. Press Reset Switch SW1 to ensure that the
AD9786 is in default mode. The default mode for the AD9786 is
for the interpolation set to 1×. The modulator is turned off in
default mode. The nominal operating currents for the evaluation
board in the power-up default mode are shown in Table 39.
Table 39. Nominal Operating Currents in Power-Up Default
Mode
Evaluation Board
Power Supply
DVDD
CLKVDD
ACVDD/ADVDD
AVDD1
AVDD2
Table 40. SPI Registers
Register
0x01
SERIAL PORT
SW1 is a hard reset switch that sets the AD9786 to its default
state. It should be used every time the AD9786 power supply is
cycled, the clock is interrupted, or new data is to be written via
the SPI port. Set the SPI software to read back data from the
AD9786, and then verify that the expected values are read back
when the software is run.
Bit 7
INTERP[1]
50
MSPS
26
78
1
30
27
Bit 6
INTERP[0]
Nominal Current @ Speed (mA)
100
MSPS
49
83
4
30
27
Bit 5
Bit 4
150
MSPS
74
87
6
30
27
Bit 3
200
MSPS
99
92
8
30
27
Bit 0
Rev. B | Page 45 of 56
ANALOG OUTPUT
The analog output of the AD9786 is accessed via Connector S3.
Once all settings are selected and the current levels and SPI port
functionality are verified, the analog signal at S3 can be viewed.
For most of the AD9786 applications, a spectrum analyzer is the
preferred instrument to verify proper performance. A typical
spectral plot is shown in Figure 86, with the AD9786 synthesizing
a two-tone signal in the default mode with a 200 MSPS sample
rate. A single-tone CW signal should provide output power of
approximately +0.5 dBm to the spectrum analyzer.
If the spectrum does not look correct at this point, the data
input might be violating setup and hold times with respect to
the input clock. To correct this, the user should vary the input
data timing. If this is not possible, SPI Register 0x02, Bit 4
(DCLKPOL), can be inverted. This bit controls the clock edge
upon which the data is latched. If neither of these methods corrects
the spectrum, it is unlikely that the issue is timing related. In this
case, verify that all instructions have been followed correctly and
that the SPI port readback indicates the correct values.
–100
–110
–120
–10
–20
–30
–40
–50
–60
–70
–80
–90
0
REF LVL
START 100MHz
1AVG
0dBm
MARKER 1 [T1]
Figure 86. Typical Spectral Plot
193.00170300MHz
–84.96dBm
19.9MHz/
RBW
VBW
SWT
560ms
30kHz
30kHz
STOP 200MHz
UNIT
RF ATT
AD9786
20dB
dBm
1MA
A