DM385, DM388
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SPRS821D –MARCH 2013–REVISED DECEMBER 2013
8.13.2.2.2 Compatible DDR2 Devices
Table 8-48 shows the parameters of the DDR2 devices that are compatible with this interface. Generally,
the DDR2 interface is compatible with x16 DDR2-800 speed grade DDR2 devices.
Table 8-48. Compatible DDR2 Devices (Per Interface)
NO.
1
PARAMETER
MIN
MAX
UNIT
DDR2 device speed grade(1)
DDR2 device bit width
DDR2 device count(2)
DDR2-800
2
x16
1
x16
2
Bits
Devices
Balls
3
4
DDR2 device ball count(3)
84
92
(1) Higher DDR2 speed grades are supported due to inherent DDR2 backwards compatibility.
(2) One DDR2 device is used for a 16-bit DDR2 memory system. Two DDR2 devices are used for a 32-bit DDR2 memory system.
(3) The 92-ball devices are retained for legacy support. New designs will migrate to 84-ball DDR2 devices. Electrically, the 92- and 84-ball
DDR2 devices are the same.
8.13.2.2.3 PCB Stackup
The minimum stackup required for routing the device is a six-layer stackup as shown in Table 8-49.
Additional layers may be added to the PCB stackup to accommodate other circuitry or to reduce the size
of the PCB footprint.
Table 8-49. Minimum PCB Stackup
LAYER
TYPE
Signal
Plane
Plane
Signal
Plane
Signal
DESCRIPTION
Top routing mostly horizontal
Ground
1
2
3
4
5
6
Power
Internal routing
Ground
Bottom routing mostly vertical
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