i.MX6UL DDR3L Calibration Values

[michaelperreca]

Good Afternoon,

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:

Unit	0x021b080c	0x021b083c	0x021b0848	0x021b0850
1	0x00000000	0x014C014C	0x40404248	0x40405450
2	0x00000000	0x01480148	0x4040444A	0x4040544E
3	0x00000000	0x01480148	0x4040424A	0x4040544E
4	0x00000000	0x01440148	0x4040424A	0x40405650
5	0x00000000	0x01540150	0x4040464E	0x4040544E
6	0x00000000	0x014C0154	0x4040464A	0x40405452
7	0x00000000	0x01500150	0x4040464A	0x4040544E
8	0x00000000	0x014C014C	0x4040444E	0x4040544E
9	0x00000000	0x014C014C	0x4040444C	0x40405650
10	0x00000000	0x0150014C	0x40404648	0x4040544C
11	0x00000000	0x014C0150	0x4040464C	0x4040544E
12	0x00000000	0x014C0150	0x4040464C	0x4040564E
13	0x00000000	0x01580154	0x4040464A	0x4040564E
14	0x00000000	0x01540154	0x4040464E	0x4040564E
15	0x00000000	0x01480140	0x40404244	0x4040524E
16	0x00000000	0x01500150	0x4040464C	0x40405650

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?

Thanks!

-Mike

[gusarambula]

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.

http://www.nxp.com/assets/documents/data/en/application-notes/AN4467.pdf

I hope this information helps!

Regards,