AM3359 datasheet(165/236 Pages) TI

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AM3359, AM3358, AM3357

AM3356, AM3354, AM3352

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SPRS717F – OCTOBER 2011 – REVISED APRIL 2013

5.6.2.2.2.7 High-Speed Bypass Capacitors

High-speed (HS) bypass capacitors are critical for proper DDR2 interface operation. It is particularly

important to minimize the parasitic series inductance of the HS bypass capacitors, AM335x device DDR2

power, and AM335x device DDR2 ground connections. Table 5-49 contains the specification for the HS

bypass capacitors as well as for the power connections on the PCB.

Table 5-49. High-Speed Bypass Capacitors

NO.

PARAMETER

MIN

MAX

UNIT

HS bypass capacitor package size(1)

0402

10 mils

Distance from HS bypass capacitor to device being bypassed

250

mils

Number of connection vias for each HS bypass capacitor(2)

Vias

Trace length from bypass capacitor contact to connection via

mils

Number of connection vias for each AM335x VDDS_DDR and VSS terminal

Vias

Trace length from AM335x VDDS_DDR and VSS terminal to connection via

mils

Number of connection vias for each DDR2 device power and ground terminal

Vias

Trace length from DDR2 device power and ground terminal to connection via

mils

AM335x VDDS_DDR HS bypass capacitor count(3)

Devices

AM335x VDDS_DDR HS bypass capacitor total capacitance

0.6

μF

DDR2 device HS bypass capacitor count(3)(4)

Devices

DDR2 device HS bypass capacitor total capacitance(4)

0.4

μF

(1) LxW, 10-mil units; for example, 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) Per DDR2 device.

5.6.2.2.2.8 Net Classes

Table 5-50 lists the clock net classes for the DDR2 interface. Table 5-51 lists the signal net classes, and

associated clock net classes, for the signals in the DDR2 interface. These net classes are used for the

termination and routing rules that follow.

Table 5-50. Clock Net Class Definitions

CLOCK NET CLASS

AM335x PIN NAMES

DDR_CK and DDR_CKn

DQS0

DDR_DQS0 and DDR_DQSn0

DQS1

DDR_DQS1 and DDR_DQSn1

Table 5-51. Signal Net Class Definitions

ASSOCIATED CLOCK

SIGNAL NET CLASS

AM335x PIN NAMES

NET CLASS

ADDR_CTRL

DDR_BA[2:0], DDR_A[15:0], DDR_CSn0, DDR_CASn, DDR_RASn,

DDR_WEn, DDR_CKE, DDR_ODT

DQ0

DQS0

DDR_D[7:0], DDR_DQM0

DQ1

DQS1

DDR_D[15:8], DDR_DQM1

Peripheral Information and Timings

165

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