We have a system where one 7044 on each PCB provides the clock and SYSREF signals for the 4 ADCs. The system consists of 20 of these PCBs with 320 receive channels. At room temperature, the system simultaneously acquires signals under the action of SYNC and performs phase correction, so that the phase of the signal received by the 320 channels is consistent with that of the reference channel. When the ambient temperature rises to 50 degrees Celsius, the phase consistency of the 320 channels is verified by using the phase correction factor calculated at room temperature, and it is found that a small number of channels have a phase difference of about 20 degrees from the reference channel.
According to the description of VCO calibration in the D version of the 7044's datasheet:
1.We read the value of 0x008C register and look at the capacitor bank calculated by the autotune algorithm. We found that when the temperature increased, the register value read from part of the 7044 increased by 1 compared to room temperature, and the PCBs with a phase difference of 20 degrees were the register value changed.
2.Keeping the ambient temperature unchanged (50 degrees Celsius), re-energizing after power-off, and testing again found that the 7044 with the previous register value changed returned to the value at room temperature, while some did not recover, and the new 7044 register value also changed.
Therefore, our experimental results show that at different temperatures, the auto-tuning algorithm will calculate different capacitance banks, which leads to a change in the clock phase of the 7044 output with the change of register value, so that the phase difference between the phase of the signal collected by the ADC and the reference signal after correction occurs.
I wonder if our conclusions are correct and if so, how to avoid this, as our products need to work properly at different temperatures and cannot tolerate such large phase differences.
Thank you so much for helping。
By the way, there is a similar question in the forum with the topic:
