I'm trying to get a AD9910 on a board I ordered on ebay to work. To control the chip, I'm using a STM32F103 "Blue Pill"-Board and a simple Arduino-Sketch to write the data into the chip to put out a 10 MHz-Signal.
However, all I get is a weak (-42 dBm) signal at 360 MHz when I power up the chip. Doesn't matter what I try with the control-board, the output stays the same.
If I disconnect the on board 40 MHz-Oscillator, the 360 Mhz-Signal turns into a ca. 40 Mhz wide increase in noise on the spectrum analyzer (centered around 360 MHz) - so at least something is happening inside the chip.
Following a suggestion from another question here, I checked the Sync OUT and REF-CLK OUT pins.
REF_CLK OUT is sitting at 1,8 V with a 20 mVpp signal on it (looks like some interference from the 40 MHz Input), and Sync OUT is doing nothing either.
Also the chip isn't getting warm and PLL_LOCK stays LOW all the time.
The EXT_PWR_DOWN Pin is at 0 V btw. And Master Reset is also pulled down to 0 V.
My question now: Is the chip okay with REF_CLK_OUT and SYNC-OUT missing after power up or a reset?