2.4.4.3 DDR2/mDDR
- Parallel termination is not allowed on CLKP/CLKN pins.
- If termination is used, the DDR2/mDDR drive strength should be set to full strength. Otherwise, the drive strength should be set to half strength.
- No pullups or stubs are allowed on any DDR pins.
- For DQS and D net classes:
- Routes must be point-to-point.
- Skew matching across bytes is not needed nor recommended.
- Skew between the two classes should not exceed 25 mil.
- Clock and DQS net class trace lengths need to be routed such that the skew between the two net classes meets the tDQSS timing parameter.
For additional guidance, see Understanding TI’s PCB routing rule-based DDR timing.