AM3359 datasheet(138/195 Pages) TI

138 / 195 page

AM3359, AM3358, AM3357

AM3356, AM3354, AM3352

SPRS717B

– OCTOBER 2011 – REVISED JANUARY 2012

www.ti.com

5.4.2.1.2.7 High-Speed Bypass Capacitors

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

important to minimize the parasitic series inductance of the HS bypass capacitors, AM335x/LPDDR

power, and AM335x/LPDDR ground connections. Table 5-30 contains the specification for the HS bypass

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

Table 5-30. 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/VSS terminal

Vias

Trace length from AM335x VDDS_DDR/VSS terminal to connection via

mils

Number of connection vias for each LPDDR device power/ground terminal

Vias

Trace length from LPDDR device power/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

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

Devices

LPDDR device HS bypass capacitor total capacitance(4)

0.4

μF

(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) Per LPDDR device.

5.4.2.1.2.8 Net Classes

Table 5-31 lists the clock net classes for the LPDDR interface. Table 5-32 lists the signal net classes, and

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

termination and routing rules that follow.

Table 5-31. Clock Net Class Definitions

CLOCK NET CLASS

AM335x PIN NAMES

DDR_CK/DDR_CKn

DQS0

DDR_DQS0

DQS1

DDR_DQS1

Table 5-32. Signal Net Class Definitions

ASSOCIATED CLOCK

SIGNAL NET CLASS

AM335x PIN NAMES

NET CLASS

ADDR_CTRL

DDR_BA[1:0], DDR_A[15:0], DDR_CSn0, DDR_CASn, DDR_RASn,

DDR_WEn, DDR_CKE

DQ0

DQS0

DDR_D[7:0], DDR_DQM0

DQ1

DQS1

DDR_D[15:8], DDR_DQM1

138

Peripheral Information and Timings

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