AD9850 datasheet(14/19 Pages) AD

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AD9850

–14–

REV. E

AD9850 Evaluation Board Instructions

Required hardware/software:

IBM compatible computer operating in a Windows environment

Printer port, 3.5" 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:

Copy the contents of the AD9850 disk onto your hard drive

(there are three files).

Connect the printer cable from computer to the AD9850

evaluation board.

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.

Connect external 50 ohm clock or remove R2 and apply a high

Z input clock such as a crystal “can” oscillator.

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

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 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.

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.

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