TMS320DM6467_09 Datasheet, PDF (219/357 Pages) Texas Instruments – Digital Media System-on-Chip

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TMS320DM6467
Digital Media System-on-Chip
SPRS403F – DECEMBER 2007 – REVISED OCTOBER 2009
7.10.2.10 VREF Routing
VREF is used as a reference by the input buffers of the DDR2 memories as well as the DM6467’s. VREF
is intended to be 1/2 the DDR2 power supply voltage and should be created using a resistive divider as
shown in Figure 7-28. Other methods of creating VREF are not recommended. Figure 7-31 shows the
layout guidelines for VREF.
VREF Bypass Capacitor
DDR2 Device
A1
VREF Nominal Minimum
Trace Width is 20 Mils
DM646x
Device
A1
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.
Figure 7-31. VREF Routing and Topology
7.10.2.11 DDR2 CK and ADDR_CTRL Routing
Figure 7-32 shows the topology of the routing for the CK and ADDR_CTRL net classes. The route is a
balanced T as it is intended that the length of segments B and C be equal. In addition, the length of A
should be maximized.
A1
A
A1
T
DM646x
Figure 7-32. CK and ADDR_CTRL Routing and Topology
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Peripheral Information and Electrical Specifications 219