I'm working on the bring up of a new custom PCB including the AD9747.
In one of the very first trials, I could get it to run a simple ramp on its output, but with no other design in my FPGA it will provide any output.
I've already tried writing all registers, writing only several, writing no registers - only toggling the reset pin after power up.
I've no idea why it won't output any data - sample rate is already reduced to 122Msps - s/h times for data and clock are well inside the limits.
The clock input is AC-coupled LVDS with 400mV VCM. The differential voltage swing on the input is ~600mV.
Sample clock is applied once configuration on SPI is finished. The differential output is connected to a simple resistor network and a differential probe.
I've checked already:
- supply pins
- FSADJ - 1.2V - 100pF in parallel tested as noted in another thread here
- REFIO - 1.2V
- DCO - 122MHz - ok
- data/clock timing
- SPI interface timing / data content
Attached some screenshots I've made during the tests.
If anybody has an idea of what could be wrong, please let me know.
Thanks, best regards