Question
We are currently using AD9129 in one of our mixed signals designs and we are confused bout the refrence plane for the analog section.1/Should it be VSSC cince it's the analog return for the analog supply or VSSA as in the relative eval board.2/ the reason behind using VDDA as shield for the diff. RF out??
Answer
1/ VSSA is a -1.5V supply to the DAC core on the chip and VDDA is a +1.8V supply. Current runs through the DAC core current steering transistors fromVDDA to VSSA.2. 1/ VSSA is a -1.5V supply to the DAC core on the chip and VDDA is a +1.8V supply. Current runs through the DAC core current steering transistorsfrom VDDA to VSSA.
The shield isolates the EVB RF output from noise sources on the board.