Uboot SDRAM output drive strength for IMX6D

[tomsaluzzo]

Using the IMX6D. Why does Uboot 2009.08 set the output drive strength for DDR3 SDRAM interface signals to 40 ohms? The Micron MT4J128M16HA-15E DDR3 SDRAM datasheet (page 134) states that 34 ohms is the primary output driver impedance setting for DDR3 SDRAM devices.

[igorpadykov]

Hi Tom

34 ohms (more powerful output) provides more noise to board

than 40 ohms, also this [40 ohms] will allow to decrease overall power consumption.

With 40 ohms DDR tests are passed successfully.

Datasheet gives recommended values which may vary in each particular use case.

Best regards

chip

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[tomsaluzzo]

You stated “With 34 ohms DDR tests are passed successfully”, but Uboot sets to 40 ohms. Did you mean to say - With 40 ohms DDR tests are passed successfully?

Are you saying either 34 ohms or 40 ohms is appropriate?

Tom Saluzzo

Field Application Engineer

Arrow Electronics

1000 Pittsford Victor Rd. 2nd Floor

Pittsford, NY 14534

585.820.2781

tsaluzzo@arrow.com

www.arrow.com <http://www.arrow.com/>

[igorpadykov]

Yes, with 40 ohms DDR tests are passed successfully.

Best regards

chip