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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.
A1
LPDDR
Device
A1
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.
1
PARAMETER
AM335x VDDS_DDR bulk bypass capacitor count
MIN
1
MAX
UNIT
Devices
μF
2
AM335x VDDS_DDR bulk bypass total capacitance
LPDDR#1 bulk bypass capacitor count
10
1
3
Devices
μF
4
LPDDR#1 bulk bypass total capacitance
LPDDR#2 bulk bypass capacitor count(2)
LPDDR#2 bulk bypass total capacitance(2)
10
1
5
Devices
μF
6
10
(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.
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