Tool/software:
Hello,
We built up a design for evaluating ADS52J65 connected to a XILINX Kintex Ultrascale of GTH transceivers. We use TI204c IP for JESD204 layer.
We could get the connection up and running over 4 JESD Lanes with 2 channel par lanes.
Test patterns are read correctly for possible pattern.
We could get ADC sampling some externally generated waveforms and lately observe some errors on samples.
Our use case is the following :
Digital Gain = 0 ; Sampling rate: 100MHz ; HPF : Off ; Demod : Off
When samples are between -2000 and +1500, everything works fine
When samples reach 1500, some sampling errors appear between values 1500 and 2000
Zoom on Positive Peak
This phenomenom is also visible on the negative potion of the signal
Zoom on negative Peak
Influence of Scambling
Zoom on positive peak with Scambling disabled:
- No changes
Influence of Digital Gain
Zoom on positive peak with digital Gain = 3
- Sampling errors are amplified corresponding to gain register
Influence of HPF
- Sampling error is filtered
Repetition of the phenomenon at various range
Sampling error around 6000 :
Sample error around 10000
Same thing seems to appear at around every multiple of 4096
Test pattern:
Selection of a Ramp pattern around incriminated value
- Ramp is behaving properly
Conclusion
ADS52J65 shows error on sampling data.
These errors appear below every multiple of 4096 in a 512 wide range (at Digital gain = 0 and HPF disabled)
This phenomenon is not related to scrambling.
Digital Gain magnifies the amplitude but does not change the shape and HPF filters the error.
- The problem is already present before digital processing stage
Ramp Test pattern is behaving properly
