SI5325C-C-GM Datasheet, PDF(110/178 Page) Silicon Laboratories

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SI5325C-C-GM Datasheet, PDF (110/178 Pages) Silicon Laboratories – ANY-FREQUENCY PRECISION CLOCKS

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Si53xx-RM

RATE[1:0]

Table 51. XA/XB Reference Sources and Frequencies

NB/WB

Type

Recommended Lower limit

No crystal or external clock

Reserved

External clock

114.285 MHz

Third overtone crystal

114.285 MHz

External clock

57.1425 MHz

109 MHz

55 MHz

Reserved

External clock

Fundamental mode crystal

38.88 MHz

40 MHz

37 MHz

Upper limit

125.5 MHz

61 MHz

41 MHz

In some applications, a crystal with frequencies other than 114.285 MHz may be used. See âAN591: Crystal

Selection for the Si5315, Si5317, and other Si53xx Any-Frequency Jitter Attenuating Clocksâ for details and a

current list of crystal vendors and approved part numbers.

External reference (and crystal) frequency values should be avoided that result in an output frequency that is an

integer or near integer multiple of the reference frequency. See Appendix B on page 112 for details.

Because the crystal is used as a jitter reference, rapid changes of the crystal temperature can temporarily disturb

the output phase and frequency. For example, it is recommended that the crystal not be placed close to a fan that

is being turned off and on. If a situation such as this is unavoidable, the crystal should be thermally isolated with an

insulating cover.

Fundamental Mode Crystals

For cost sensitive applications that do not have the most demanding jitter requirements, all of the narrow band

devices can use fundamental mode crystals that are in the lowest frequency band ranging from 37 to 41 MHz

(corresponding to RATE = LL). Unlike the other narrowband members of the family, the Si5327 is only capable of

using fundamental mode crystals that are in this range. For a more detailed discussion of the trade-offs associated

with this approach and a list of approved low frequency crystals, please see the application note AN591, which can

be downloaded from www.silabs.com/timing.

110

Rev. 1.2

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