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iMX 534 SDRAM DDR2 clock problem

Question asked by Måns Norell on Sep 26, 2016
Latest reply on Oct 6, 2016 by Måns Norell

So i've been troubleshooting a product which uses a DDR2-800 32Mx16 (MT47H32M16HR-25E IT) together with a iMX (MCIMX534AVV8C). The product is in production state and a fairly high amount (10%) are failing when the core temp of the iMx gets up to 55-60 degrees celsius.

 

I have found that the diffrential clock from iMx to DDR2, DRAM_CLK0 and #DRAM_CLK0 is acting really weird when measuring with an active diffrential probe over the termination resistor. See the attached image: the clock signal is fairly high and has parts of it going to a lower state sporadically. When the iMx gets cooled down with coolingspray the clock level is stable and fine at the lower level on the image. Also when the clock is fine after cooling spray the iMx has no problem booting even at high ambient temperature (80 deg). I am convinced that the problem has something to do with the clock.

 

I have changed the iMx and also the DDR2 memory without any change.

I have x-rayed the card to ensure proper mounting of the components.

I have probed all voltages on the card.

I have tried changing the drive strength of the clock, from 43 Ohm to 150 Ohm, but the clock is still weird.

 

Does anyone recognize this?

 

I'll attach an image of the DDR part of the schematic aswell.

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