I recently received my first prototype boards which have the i.MX6UL and 512MB of DDR3L memory.
I'm run the DDR calibration using DDR Test Tool 2.6 with no issues. What I am seeing is variation in the calibration board to board. Here are the values for all 16 boards:
My questions are as follows:
1. Why is there such variation between the boards?
2. How should I go about selecting the proper value for production settings with these variations?
3. There is obvious concerns over temperature that these settings are not proper, how should I account for temperature?
Hello Michael Perreca,
There may be small variations from board to board depending on factors such as the manufacturing process which leads to small variations. I would recommend taking a value in the middle of the range for each register and having an eye diagram on a sample of boards in order to see if the performance is the expected.
As for the variations on temperature these are accounted for in the ZQ calibration, which runs automatically at a periodic rate. You may find more information on this calibration on Application Note 4467 (link below) in section 7.2.
I hope this information helps!