AD9850 Analog Devices, AD9850 Datasheet - Page 14

• Manufacturer Part Number: AD9850
• Description: CMOS/ 125 MHz Complete DDS Synthesizer
• Manufacturer: Analog Devices

AD9850
AD9850 Evaluation Board Instructions
Required hardware/software:
IBM compatible computer operating in a Windows environment
Printer port, 3.5" floppy drive and Centronics compatible
XTAL clock or signal generator—if using a signal generator, dc
AD9850 evaluation board software disk and AD9850/FSPCB or
+5 V voltage supply
Setup:
Copy the contents of the AD9850 disk onto your hard drive
Connect the printer cable from computer to the AD9850
Apply power to AD9850 evaluation board. The AD9850 is
The AD9850 may be powered with 3.3 V to +5 V.
Connect external 50 ohm clock or remove R2 and apply a high
Locate the file called 9850REV2.EXE and execute that program.
Monitor should display a “control panel” to allow operation of
Operation:
On the control panel, locate the box called “COMPUTER I/O.”
Point to and click the selection marked LPT1 and then point to
the “TEST” box and click. A message will appear telling you if
your choice of output ports is correct. Choose other ports as
necessary to achieve a correct setting. If you have trouble getting
your computer to recognize any printer port, try the following:
connect three 2K pull-up resistors from Pins 9, 8 and 7 of U3 to
+5 V. This will assist “weak” printer port outputs in driving the
heavy capacitance load of the printer cable. If troubles persist,
try a different printer cable.
Locate the “MASTER RESET” button with the mouse and
click it. This will reset the AD9850 to 0 Hz, 0 degrees phase.
The output should be a dc voltage equal to the full-scale output
of the AD9850.
printer cable.
offset the signal to one-half the supply voltage and apply at
least 3 V p-p signal across the 50 Ω (R2) input resistor.
Remove R2 for high Z clock input.
AD9850/CGPCB evaluation board.
(there are three files).
evaluation board.
powered separately from the connector marked “DUT +V.”
Z input clock such as a crystal “can” oscillator.
the AD9850 evaluation board.
–14–
Locate the “CLOCK” box and place the cursor in the frequency
box. Type in the clock frequency (in MHz) that you will be
applying to the AD9850. Click the LOAD button or press enter
on the keyboard.
Move the cursor to the OUTPUT FREQUENCY box and type in
the desired output frequency (in MHz). Click the “LOAD” button
or press the enter key. The BUS MONITOR section of the
control panel will show the 32-bit word that was loaded into the
AD9850. Upon completion of this step, the AD9850 output
should be active and outputting your frequency information.
Changing the output phase is accomplished by clicking on the
“down arrow” in the OUTPUT PHASE DELAY box to make
a selection and then clicking the LOAD button.
Other operational modes (Frequency Sweeping, Sleep, Serial
Input) are available to the user via keyboard/mouse control.
The AD9850/FSPCB provides access into and out of the on-chip
comparator via test point pairs (each pair has an active input and a
ground connection). The two active inputs are labeled TP1 and
TP2. The unmarked hole next to each labeled test point is a
ground connection. The two active outputs are labeled TP5 and
TP6. Unmarked ground connections are adjacent to each of these
test points.
The AD9850/CGPCB provides BNC inputs and outputs associ-
ated with the on-chip comparator and the onboard, 5th order,
200 ohm input/output Z, elliptic 45 MHz low-pass filter. Jumper-
ing (soldering a wire) E1 to E2, E3 to E4, and E5 to E6 connects
the onboard filter and the midpoint switching voltage to the
comparator. Users may elect to insert their own filter and com-
parator threshold voltage by removing the jumpers and inserting
a filter between J7 and J6 and then providing a threshold voltage
at E1.
If you choose to use the XTAL socket to supply the clock to the
AD9850, you must remove R2 (a 50 ohm chip resistor). The
crystal oscillator must be either TTL or CMOS (preferably)
compatible.
REV. E