OMAP-L138_16 Datasheet, PDF (134/286 Pages) Texas Instruments – OMAP-L138 C6000 DSP ARM Processor

OMAP-L138
SPRS586I – JUNE 2009 – REVISED SEPTEMBER 2014
www.ti.com
6.11.3.6 Bulk Bypass Capacitors
Bulk bypass capacitors are required for moderate speed bypassing of the DDR2/mDDR and other
circuitry. Table 6-31 contains the minimum numbers and capacitance required for the bulk bypass
capacitors. Note that this table only covers the bypass needs of the Soc and DDR2/mDDR interfaces.
Additional bulk bypass capacitance may be needed for other circuitry.
Table 6-31. Bulk Bypass Capacitors
NO. PARAMETER
1 DDR_DVDD18 Supply Bulk Bypass Capacitor Count⁽¹⁾
MIN
MAX
UNIT
3
Devices
2 DDR_DVDD18 Supply Bulk Bypass Total Capacitance
3 DDR#1 Bulk Bypass Capacitor Count⁽¹⁾
30
μF
1
Devices
4 DDR#1 Bulk Bypass Total Capacitance
5 DDR#2 Bulk Bypass Capacitor Count⁽¹⁾⁽²⁾
6 DDR#2 Bulk Bypass Total Capacitance⁽²⁾
22
μF
1
Devices
22
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 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, Soc/DDR2/mDDR
power, and Soc/DDR2/mDDR ground connections. Table 6-32 contains the specification for the HS
bypass capacitors as well as for the power connections on the PCB.
Table 6-32. High-Speed Bypass Capacitors
NO. PARAMETER
1 HS Bypass Capacitor Package Size⁽¹⁾
MIN
MAX
0402
2 Distance from HS bypass capacitor to device being bypassed
3 Number of connection vias for each HS bypass capacitor
250
2 ⁽²⁾
4 Trace length from bypass capacitor contact to connection via
1
30
5 Number of connection vias for each DDR2/mDDR device power or ground balls
1
6 Trace length from DDR2/mDDR device power ball to connection via
7 DDR_DVDD18 Supply HS Bypass Capacitor Count⁽³⁾
35
10
8 DDR_DVDD18 Supply HS Bypass Capacitor Total Capacitance
0.6
9 DDR#1 HS Bypass Capacitor Count⁽³⁾
8
10 DDR#1 HS Bypass Capacitor Total Capacitance
0.4
11 DDR#2 HS Bypass Capacitor Count⁽³⁾⁽⁴⁾
8
12 DDR#2 HS Bypass Capacitor Total Capacitance⁽⁴⁾
0.4
(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.
UNIT
10 Mils
Mils
Vias
Mils
Vias
Mils
Devices
μF
Devices
μF
Devices
μF
134 Peripheral Information and Electrical Specifications
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