DDR3 SDRAM memory interface termination and layout guidelines

DDR3 SDRAM offers features designed to improve signal integrity of increased bus speed. While some of the features are already available in DDR2 SDRAM, these features are further enhanced in DDR3 SDRAM.

For example, the ODT feature is available in both DDR2 and DDR3 SDRAM, but in DDR3 SDRAM, the values of the ODT are based on the value of an external resistor—the RZQ resistor. In addition to using this ZQ resistor for setting the ODT value, it is also used for calibrating the ODT value so that it maintains its resistance value to within a 10 percent tolerance. This application note describes the following updated and new features in DDR3 SDRAM.

View the PDF document for more information.