I recently purchased an ad5791 Eval board along with an smp-b board to connect it to the computer. I did the following:
connected vdd to +15V
connected vss to -15V
connected agnd to 0V
I did these things following the ug-185 datasheet, specifically page 3 and 8.
I then plugged the board into the usb connector and ran the software that came with it. It searched for usb devices, found the eval board and made it blink asking me if that was the device I wanted to connect. It was and I clicked select. Now, the output of the eval board, Vout, I connected to an oscilloscope and hit start on the Measure DAC Output of the associated software and found no response. However, when I connected Voutbuff to the oscilloscope and hit start, the signal becomes very noisy and clearly responds to the computer software in some way. I do not know what to do next, the datasheet seems to specify that the Vref=+5V is enough to generate the Vrefn and Vrefp as suggested in Table 4 on page 3.
Any suggestions as to what to do would be very helpful, I have been trying everything and have left the links in the default positions. Please help me.