Miscellaneous Signals; Ddrcomp Resistive Compensation; Ddrcvol And Ddrcvoh Resistive Compensation - Intel Xeon Design Manual

6.8

Miscellaneous Signals

The MCH uses a compensation signal to adjust buffer characteristics and output voltage swing over
temperature, process, and voltage skew. Calibration is done periodically by sampling the
DDRCOMP, DDRCVOH, and DDRCVOL pins on the MCH. Connect DDRCOMP to the DDR
termination voltage (1.25 V) through a 6.81 Ω ± 1% resistor as illustrated in
the resistor within 1 in. of the MCH. Likewise, keep the voltage divider networks within 1 in. of the
MCH (see
Figure 6-14. DDRCOMP Resistive Compensation
Figure 6-15. DDRCVOL and DDRCVOH Resistive Compensation
MCH
Design Guide
Figure 6-15).
MCH
DDR VDD
(2.5V)
13 kΩ ± 1%
< 1"
DDRCVOH
0.01 µF
7 kΩ ±
1%
DDR VTERM
(1.25V)
Memory Interface Routing Guidelines
DDR VTERM
(1.25 V)
6.81 Ω ± 1%
<1"
DDRCOMP
MCH
DDRCVOL
0.01 µF
Figure 6-14, and place
DDR VTERM
(1.25V)
7 kΩ ± 1%
< 1"
0.01 µF 0.01 µF
13 kΩ ±
1%
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