TMS320DM647 datasheet(97/181 Pages) TI

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TMS320DM647

TMS320DM648

www.ti.com

SPRS372F – JANUARY 2010 – REVISED SEPTEMBER 2009

6.9.3.3

PCB Stackup

The minimum stackup required for routing the device is a six-layer stack as shown in Table 6-29.

Additional layers may be added to the PCB stack up to accommodate other circuity or to reduce the size

of the PCB footprint.

Table 6-29. Minimum PCB Stack Up

LAYER

TYPE

DESCRIPTION

Signal

Top routing mostly horizontal

Plane

Ground

Plane

Power

Signal

Internal routing

Plane

Ground

Signal

Bottom routing mostly vertical

Complete stack up specifications are provided in Table 6-30.

Table 6-30. PCB Stack Up Specifications

NO.

PARAMETER

MIN

TYP

MAX

UNIT

PCB Routing/Plane Layers

Signal Routing Layers

Full ground layers under DDR2 routing Region

Number of ground plane cuts allowed within DDR routing region

Number of ground reference planes required for each DDR2 routing layer

Number of layers between DDR2 routing layer and reference ground plane

PCB Routing Feature Size

Mils

PCB Trace Width w

Mils

PCB BGA escape via pad size

Mils

PCB BGA escape via hole size

Mils

DSP Device BGA pad size(1)

DDR2 Device BGA pad size(2)

Single Ended Impedance, Zo

Ω

Impedance Control(3)

Z-5

Z+5

Ω

(1)

See the Flip Chip Ball Grid Array Package Reference Guide (SPRU811) for DSP device BGA pad size.

(2)

See the DDR2 device manufacturer documenation for the DDR2 device BGA pad size.

(3)

Z is the nominal singled ended impedance selected for the PCB specified by item 12.

6.9.3.4

Placement

Figure 6-13 shows the required placement for the device as well as the DDR2 devices. The dimensions

for Figure 6-13 are defined in Table 6-31. The placement does not restrict the side of the PCB where the

devices are mounted. The purpose of the placement is to limit the maximum trace lengths and allow for

proper routing space. For 16-bit DDR memory systems, the high word DDR2 device is omitted from the

placement.

Peripheral Information and Electrical Specifications

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