AM3359 datasheet(153/236 Pages) TI

153 / 236 page

LPDDR

Device

AM3359, AM3358, AM3357

AM3356, AM3354, AM3352

www.ti.com

SPRS717F – OCTOBER 2011 – REVISED APRIL 2013

5.6.2.1.2.5 LPDDR Keepout Region

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

keepout region is defined for this purpose and is shown in Figure 5-35. This region should encompass all

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

clearances required for the keepout region are shown in Table 5-35. Non-LPDDR signals should not be

routed on the same signal layer as LPDDR signals within the LPDDR keepout region. Non-LPDDR signals

may be routed in the region provided they are routed on layers separated from LPDDR 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 5-35. LPDDR Keepout Region

5.6.2.1.2.6 Bulk Bypass Capacitors

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

Table 5-36 contains the minimum numbers and capacitance required for the bulk bypass capacitors. Note

that this table only covers the bypass needs of the AM335x LPDDR interface and LPDDR devices.

Additional bulk bypass capacitance may be needed for other circuitry.

Table 5-36. 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

LPDDR#1 bulk bypass capacitor count

Devices

LPDDR#1 bulk bypass total capacitance

μF

LPDDR#2 bulk bypass capacitor count(2)

Devices

LPDDR#2 bulk bypass total capacitance(2)

μF

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

(HS) bypass capacitors.

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

Peripheral Information and Timings

153

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