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AM1808
SPRS653E – FEBRUARY 2010 – REVISED MARCH 2014
6.11.3.10 VREF Routing
VREF is used as a reference by the input buffers of the DDR2/mDDR memories as well as the device.
VREF is intended to be half the DDR2/mDDR power supply voltage and should be created using a
resistive divider as shown in
Figure 6-20
shows the layout guidelines for VREF.
DDR2/mDDR Device
VREF Nominal Minimum
Trace Width is 20 Mils
118
Peripheral Information and Electrical Specifications
Figure
6-16. Other methods of creating VREF are not recommended.
VREF Bypass Capacitor
A1
A1
Figure 6-20. VREF Routing and Topology
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DDR2/mDDR
Neck down to minimum in BGA escape
regions is acceptable. Narrowing to
accomodate via congestion for short
distances is also acceptable. Best
performance is obtained if the width
of VREF is maximized.
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