AD9850

–14–

REV. H

AD9850 Evaluation Board Instructions

Required Hardware/Software

• IBM compatible computer operating in a Windows environment.

• Printer port, 3.5 inch floppy drive, and Centronics compatible

printer cable.

• XTAL clock or signal generator—if using a signal generator,

dc 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 evaluation board software disk and AD9850/FSPCB

or AD9850/CGPCB evaluation board.

• 5 V voltage supply.

Setup

1. Copy the contents of the AD9850 disk onto your hard drive

(there are three files).

2. Connect the printer cable from your computer to the AD9850

evaluation board.

3. Apply power to AD9850 evaluation board. The AD9850 is

powered separately from the connector marked DUT +V.

The AD9850 may be powered with 3.3 V to 5 V.

4. Connect external 50

Ω clock or remove R2 and apply a high

Z input clock such as a crystal can oscillator.

5. Locate the file called 9850REV2.EXE and execute that program.

6. Monitor should display a control panel to allow operation of

the AD9850 evaluation board.

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 users if

their choice of output ports is correct. Choose other ports as

necessary to achieve a correct setting. If they have trouble get-

ting their computer to recognize any printer port, they should

try the following: connect three 2 k

Ω pull-up resistors from Pins

9, 8, and 7 of U3 to 5 V. This will assist weak printer port out-

puts 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

° phase. The output

should be a dc voltage equal to the full-scale output of the

AD9850.

Locate the CLOCK box and place the cursor in the frequency

box. Type in the clock frequency (in MHz) that the user 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 the user's 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 on-board, fifth-order,

200

Ω input/output Z, elliptic, 45 MHz, low-pass filter. Jumpering

(soldering a wire) E1 to E2, E3 to E4, and E5 to E6 connects the

on-board filter and the midpoint switching voltage to the com-

parator. Users may elect to insert their own filter and compara-

tor threshold voltage by removing the jumpers and inserting a

filter between J7 and J6 and then providing a threshold voltage

at E1.

If users choose to use the XTAL socket to supply the clock to

the AD9850, they must remove R2 (a 50

Ω chip resistor).

The crystal oscillator must be either TTL or CMOS (prefer-

ably) compatible.