Advantech EVA-X4300, User Manual

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EVA-X4300 System Design Guide 18
i. EVA-X4300:
ii. DDR2 SDRAM:
16. VREF is not a high current supply, but it is important to keep it as quiet as possi-
ble with minimum inductance. For VREF, the minimum trace width is
20 mil , and
keeps overall trace length as short as possible.
17. The VREF divider resistors can be placed close to the DDR2 devices.
18. The decoupling capacitors for VREF are intended to reduce AC noise. Place
one each at the divider and every VREF input of the DDR2(s).
19. Recommended Terminations for DDR2 interface:
Signal Impedance ( Ω ) Value ( Ω ) Note
Clock±
Differential, 90
33
Near EVA-X4300
DQS± Near DDR2
A[0..13], BA[0..2], Controls
60
Near EVA-X4300
DQM
DQ[0..15] Near DDR2
MD[0..15] Near EVA-X4300
Note! Termination value may have to be adjusted according to manufacturing
condition.