on Friday i ran into a problem with the AD9833 on my prototype-PCB of my final project.
After changing a part (not the AD9833) i discovered a direct connection between AGND and DGND. I started measuring my Schottky-diodes, which connect AGND and DGND, result: the work just fine. I measured all the Voltages, also all are fine. Then I changed the AD9833. I found out, that the connection between AGND and DGND came from the AD9833 and was through the IC. I never had this problem in any measurement before, every time I checked the connection between AGND and DGND i only was able to measure the Voltage over my diodes (as it should be).
After changing the AD9833 the Problem occurred again. So I started measuring the device in operation.
The Master-Clock is just fine, not a perfect square, but hits 5V and 0V. (I know that it should be this way)
I also checked the Data I get from my microcontroller over SPI. It is correct and all states and the timing fits the specs.
The problem now is the output-signal. I programmed the AD9833 to 50kHz and triangle-output, but my Output is only this:
I've checked my setup multiple times and made sure everything is correct. It worked in the previous Prototype. I also tried to connect the grounds together, but the signal stayed the same.
You can find the circuit diagram here:
Any help is very appreciated.
Thanks for the Help,
kind Regards, Hendrik