Texas Instruments AM1808 - Page 118

A1
A1
DDR2/mDDRDevice
VREFNominalMinimum
TraceWidthis20Mils
VREFBypassCapacitor
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.
DDR2/mDDR
AM1808
SPRS653E –FEBRUARY 2010–REVISED MARCH 2014 www.ti.com
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 6-16. Other methods of creating VREF are not recommended.
Figure 6-20 shows the layout guidelines for VREF.
Figure 6-20. VREF Routing and Topology
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