For my senior design project at Miss. State University, we have to program the AD5930 to do a frequency sweep. We have it programmed to start at 100khz, and increase in frequency by 100khz every time the control pin is toggled. We are using a pic 24 to interface with the ad5930 and a 50MHZ oscillator to frame the data transfers and the sweep. We're pretty sure that we did everything correctly (hardware and software) because we were able to produce a frequency sweep several times! It will work good for a week or maybe two, and then we will try to test it again, and it will not sweep at all. We haven't changed any hardware or code, so we figure if it works one time, it should function the same way every time . We even placed a new ad5930 on the breadboard, and this solved the problem for about a week or two. After that, the ad5930 was back to it's old tricks (not sweeping when we would command it to, and outputting an ugly pointy sine wave). We also designed a PCB using the same setup we used on Breadboard. This even worked for a few test runs. But now the PCB is behaving the same way as the breadboard. We know that the chip is sufficiently powered. AVDD and DVDD are both getting sufficient voltages within the limits. We are concerned with pin2 (ref). It is only getting around 600 mv when it's supposed to get 1.18V.
Can someone please give me any tips/suggestions/ideas. It wrecks my brain how this thing works one week, and the next it will not respond to our commands. Also please see the attached word document . I have a list of additional questions and things we have tried.