AM652X datasheet(152/277 Pages) TI1

152 / 277 page

CL=

C C

(C +C )

SPRS932_CLOCK_03

152

AM6548, AM6528, AM6546

AM6526, AM6527

SPRSP08I – NOVEMBER 2017 – REVISED DECEMBER 2019

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Specifications

NOTE

The load capacitors, Cf1 and Cf2 in Figure 5-16, should be chosen such that the below

equation is satisfied. CL in the equation is the load specified by the crystal manufacturer. All

discrete components used to implement the oscillator circuit should be placed as close as

possible to the associated oscillator OSC1_XI, OSC1_XO, and VSS pins.

Figure 5-16. Load Capacitance Equation

The crystal must be in the fundamental mode of operation and parallel resonant. Table 5-24 summarizes

the required electrical constraints.

Table 5-24. OSC1 Crystal Electrical Characteristics

NAME

DESCRIPTION

MIN

TYP

MAX

UNIT

Parallel resonance crystal frequency

19.2, 20, 24, 25, 26, 27

MHz

Cf1

Cf1 load capacitance for crystal parallel resonance with Cf1 = Cf2

Cf2

Cf2 load capacitance for crystal parallel resonance with Cf1 = Cf2

ESR(Cf1,Cf2)

Crystal ESR

100

Crystal shunt capacitance

ESR = 30 Ω

ESR = 40 Ω

19.2 MHz, 20 MHz, 24

MHz, 25 MHz, 26 MHz, 27

MHz

ESR = 50 Ω

19.2 MHz, 20 MHz

24 MHz, 25 MHz, 26 MHz,

27 MHz

ESR = 60 Ω

19.2 MHz, 20 MHz

24 MHz, 25 MHz, 26 MHz,

27 MHz

Not Supported

ESR = 80 Ω

19.2 MHz, 20 MHz

24 MHz, 25 MHz, 26 MHz,

27 MHz

Not Supported

ESR = 100 Ω

19.2 MHz, 20 MHz

24 MHz, 25 MHz, 26 MHz,

27 MHz

Not Supported

Crystal motional inductance for fp = 20 MHz

10.16

Crystal motional capacitance

3.42

fj(OSC1_XI)

Frequency accuracy, OSC1_XI

Ethernet RGMII and RMII

not used

±100

ppm

Ethernet RGMII and RMII

using derived clock

±50

When selecting a crystal, the system design must consider the temperature and aging characteristics of a

based on the worst case environment and expected life expectancy of the system.

Table 5-25 details the switching characteristics of the oscillator and the requirements of the input clock.

Table 5-25. OSC1 Switching Characteristics – Crystal Mode

NAME

DESCRIPTION

MIN

TYP

MAX

UNIT

Oscillation frequency

19.2, 20, 24, 25, 26, 27

MHz

tsX

Start-up time

2(1)

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