We use the AD9858 Direct Digital Synthesizer on our RF Controller board, which I inherited from a previous design engineer who has left the company. I have a couple questions pertaining to its function that I was hoping you could provide some guidance. See attached schematic page for circuit.
- We are performing a modification to the internal divide-by-2 circuit where we are applying ground to DVDD pins and power to a DGND pin. I can’t find information explaining what exactly this is doing, but I believe the engineer received this configuration from ADI directly. Is this a valid configuration and could you explain how/why this works?
- The SYNCLK output is not a 3.3V signal when I measure it on my board. What I see is a clock signal that is centered on 1.7V and is 300mV peak-to-peak. Is the SYNCLK pin a CMOS output pin? Should it be 0V to 3.3V?