Why are there no series resistors on all of the signals to the DDR memory on the i.MX31 LITEKIT?

The i.MX31 LITEKIT excludes the series resistors on the DDR interface for these reasons:

  • Freescale testing on the IMX31 ADS kit found that series resistors provided little to no signal integrity improvement on DDR lines.
  • Low power (mobile) DDR has drive strength control on chip.
  • i.MX31 CPU has some drive strength control on DDR lines.
  • All EMC compliance testing passed without series resistors.

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