AM1808AZCED3 datasheet(118/264 Pages) TI

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AM1808

SPRS653A – FEBRUARY 2010 – REVISED APRIL 2010

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Figure 6-22 shows the topology and routing for the DQS and DQ net class; the routes are point to point.

Skew matching across bytes is not needed nor recommended.

Figure 6-22. DQS and DQ Routing and Topology

Table 6-35. DQS and DQ Routing Specification

No.

Parameter

Min

Typ

Max

Unit

Notes

DQS E Skew Length Mismatch

Mils

Center to center DQS to other DDR2/mDDR trace

4w (1)

See Note (2)

spacing

DQS/D nominal trace length

DQLM-50

DQLM

DQLM+50

Mils

See Notes (3), (4)

D to DQS Skew Length Mismatch

100

Mils

See Note (4)

D to D Skew Length Mismatch

100

Mils

See Note (4)

Center to center D to other DDR2/mDDR trace

4w (1)

See Notes (2), (5)

spacing

Center to Center D to other D trace spacing

3w (1)

See Notes (6), (2)

DQ/DQS E Skew Length Mismatch

100

Mils

See Note (4)

(1)

w = PCB trace width as defined in Table 6-27 .

(2)

Center to center spacing is allowed to fall to minimum (w) for up to 500 mils of routed length to accommodate BGA escape and routing

congestion.

(3)

Series terminator, if used, should be located closest to DDR.

(4)

There is no need and it is not recommended to skew match across data bytes, i.e., from DQS0 and data byte 0 to DQS1 and data byte

(5)

D's from other DQS domains are considered other DDR2/mDDR trace.

(6)

DQLM is the longest Manhattan distance of each of the DQS and D net class.

118

Peripheral Information and Electrical Specifications

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