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AM1808
SPRS653E – FEBRUARY 2010 – REVISED MARCH 2014
6.11.3.6 Bulk Bypass Capacitors
Bulk bypass capacitors are required for moderate speed bypassing of the DDR2/mDDR and other
circuitry.
Table 6-29
capacitors. Note that this table only covers the bypass needs of the device and DDR2/mDDR interfaces.
Additional bulk bypass capacitance may be needed for other circuitry.
NO.
PARAMETER
1
DDR_DVDD18 Supply Bulk Bypass Capacitor Count
2
DDR_DVDD18 Supply Bulk Bypass Total Capacitance
3
DDR#1 Bulk Bypass Capacitor Count
4
DDR#1 Bulk Bypass Total Capacitance
5
DDR#2 Bulk Bypass Capacitor Count
6
DDR#2 Bulk Bypass Total Capacitance
(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 caps.
(2) Only used on dual-memory systems.
6.11.3.7 High-Speed Bypass Capacitors
High-speed (HS) bypass capacitors are critical for proper DDR2/mDDR interface operation. It is
particularly important to minimize the parasitic series inductance of the HS bypass cap,
device/DDR2/mDDR power, and device/DDR2/mDDR ground connections.
specification for the HS bypass capacitors as well as for the power connections on the PCB.
NO.
PARAMETER
1
HS Bypass Capacitor Package Size
2
Distance from HS bypass capacitor to device being bypassed
3
Number of connection vias for each HS bypass capacitor
4
Trace length from bypass capacitor contact to connection via
5
Number of connection vias for each DDR2/mDDR device power or ground balls
6
Trace length from DDR2/mDDR device power ball to connection via
7
DDR_DVDD18 Supply HS Bypass Capacitor Count
8
DDR_DVDD18 Supply HS Bypass Capacitor Total Capacitance
9
DDR#1 HS Bypass Capacitor Count
10
DDR#1 HS Bypass Capacitor Total Capacitance
11
DDR#2 HS Bypass Capacitor Count
12
DDR#2 HS Bypass Capacitor Total Capacitance
(1) LxW, 10 mil units, i.e., a 0402 is a 40x20 mil surface mount capacitor
(2) An additional HS bypass capacitor can share the connection vias only if it is mounted on the opposite side of the board.
(3) These devices should be placed as close as possible to the device being bypassed.
(4) Only used on dual-memory systems.
116
Peripheral Information and Electrical Specifications
contains the minimum numbers and capacitance required for the bulk bypass
Table 6-29. Bulk Bypass Capacitors
(1)
(1)
(1) (2)
(2)
Table 6-30. High-Speed Bypass Capacitors
(1)
(3)
(3)
(3) (4)
(4)
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MIN
3
30
1
22
1
22
MIN
(2)
2
1
1
10
0.6
8
0.4
8
0.4
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MAX
UNIT
Devices
μF
Devices
μF
Devices
μF
Table 6-30
contains the
MAX
UNIT
0402
10 Mils
250
Mils
Vias
30
Mils
Vias
35
Mils
Devices
μF
Devices
μF
Devices
μF
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