AD9854 Analog Devices, AD9854 Datasheet - Page 37

• Manufacturer Part Number: AD9854
• Description: CMOS 300 MHz Quadrature Complete-DDS
• Manufacturer: Analog Devices

The control software for the AD9854/PCB evaluation board is
provided on a CD. This brief set of instructions should be used
in conjunction with the AD9854/PCB evaluation board schematic.
Several numerical entries, such as frequency and phase infor-
mation, require that the ENTER key by pressed to register
that information.
1. Select the proper printer port. Click the “Parallel Port” selec-
2. Normal operation of the AD9854/PCB evaluation board be-
3. The next programming block should be the “Reference Clock
REV. 0
tion in the menu bar. Select the port that matches your PC.
If unknown, experiment by performing the following on the
selected port. With the part powered up, properly clocked and
connected to the PC, select a port and go to the “Mode and
Frequency” menu and click the “Reset DUT and Initialize
Registers” button. Then go to the “Clock and Amplitude”
menu. Once there, click the box next to “Bypass Inverse Sinc
Filter” . . . a check mark will appear in the box . . . next click
the button “Send Control Info to DUT.” If the proper port
has been selected, the supply current going to the AD9854/
PCB evaluation board should drop by approximately 1/3 when
the inverse sinc filters are bypassed. Conversely, the supply
current will increase approximately 1/3 when the inverse sinc
filters are engaged.
gins with a master reset. Many of the default register values
after reset are depicted in the software “control panel.” The
reset command sets the DDS output amplitude to minimum
and 0 Hz, 0 phase-offset as well as other states listed in the
AD9854 Register Layout table in the preliminary data sheet.
and Multiplier” since this information is used to determine
the proper 48-bit frequency tuning words that will be entered
and calculated later.
–37–
4. The output amplitude defaults to the 12-bit straight binary
5. Refer to this data sheet and evaluation board schematic to
Applications assistance is available for the AD9854, the
AD9854/PCB evaluation board, and all other Analog Devices
products. Please call 1/800-ANALOGD.
multiplier values of the I and Q multiplier registers of 000hex
and no output should be seen from the DACs. User should
now set both multiplier amplitudes in the Output Amplitude
window to a substantial value, such as FFFhex. You may
bypass the digital multiplier by clicking the box “Output
Amplitude is always Full-Scale” but experience has shown
that doing so does not result in best SFDR. It is interesting
to note that best SFDR, as much as 11 dB better, is obtained
by routing the signal through the digital multiplier and “backing
off” on the multiplier amplitude. For instance, FC0 hex
produces less spurious signal amplitude than FFF hex. Its a
repeatable phenomenon that should be investigated exploited
for maximum SFDR (spurious-free dynamic range).
understand all the functions of the AD9854 available to the
user and to gain an understanding of what the software is
doing in response to programming commands.
AD9854