Ddr Driver Compensation; Ddr Driver Compensation Circuitry - Intel 80331 Design Manual

3.3

DDR Driver Compensation

External reference resistors are used to control slew rate and driver impedance. The
DDRIMPCRES (or DDRDRVCRES) resistor directly controls the on-die termination (ODT). The
recommendations are as follows:
•
DDRIMPCRES: controls on-die termination, DDR - 385 ohms, DDRII - 285 ohms. Note that
the closest standard 1% resistors are acceptable
•
DDRSLWRCRES: controls slew rate and driver impedance, DDR 845 ohms, DDRII
825 ohms.
With these values the ODT is 150/75 ohms for DDRII and 200/100 ohms for DDR.
Figure 9.

DDR Driver Compensation Circuitry

Intel® 80331 I/O Processor Design Guide
.
DDRIMPCRES
DDRCRES0
DDRSLWCRES
Terminations
385 ohms DDR
285 ohms DDRII
845 ohms DDR
825 ohms DDRII
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