AM3359 datasheet(160/195 Pages) TI

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DDR3 Keepout Region

DDR3 Interface

Encompasses Entire

DDR3 Routing Area

AM3359, AM3358, AM3357

AM3356, AM3354, AM3352

SPRS717B

– OCTOBER 2011 – REVISED JANUARY 2012

www.ti.com

5.4.2.3.3.5 DDR3 Keepout Region

The region of the PCB used for DDR3 circuitry must be isolated from other signals. The DDR3 keepout

region is defined for this purpose and is shown in Figure 5-45. This region should encompass all DDR3

circuitry and the region size varies with component placement and DDR3 routing. Additional clearances

required for the keepout region are shown in Table 5-54. Non-DDR3 signals should not be routed on the

same signal layer as DDR3 signals within the DDR3 keepout region. Non-DDR3 signals may be routed in

the region provided they are routed on layers separated from DDR3 signal layers by a ground layer. No

breaks should be allowed in the reference ground or VDDS_DDR power plane in this region. In addition,

the VDDS_DDR power plane should cover the entire keepout region.

Figure 5-45. DDR3 Keepout Region

5.4.2.3.3.6 Bulk Bypass Capacitors

Bulk bypass capacitors are required for moderate speed bypassing of the DDR3 and other circuitry.

Table 5-55 contains the minimum numbers and capacitance required for the bulk bypass capacitors. Note

that this table only covers the bypass needs of the AM335x DDR3 interface and DDR3 device(s).

Additional bulk bypass capacitance may be needed for other circuitry.

Table 5-55. Bulk Bypass Capacitors(1)

NO.

PARAMETER

MIN

MAX

UNIT

AM335x VDDS_DDR bulk bypass capacitor count

Devices

AM335x VDDS_DDR bulk bypass total capacitance

μF

DDR3#1 bulk bypass capacitor count

Devices

DDR3#1 bulk bypass total capacitance

μF

DDR3#2 bulk bypass capacitor count(2)

Devices

DDR3#2 bulk bypass total capacitance(2)

μF

(1) These devices should be placed near the devices they are bypassing, but preference should be given to the placement of the

high-speed (HS) bypass capacitors and DDR3 signal routing.

(2) Only used when two DDR3 devices are used.

160

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