SI5324C-C-GM Datasheet, PDF(19/72 Page) Silicon Laboratories – ANY-FREQUENCY PRECISION CLOCK MULTIPLIER/ JITTER ATTENUATOR

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SI5324C-C-GM Datasheet, PDF (19/72 Pages) Silicon Laboratories – ANY-FREQUENCY PRECISION CLOCK MULTIPLIER/ JITTER ATTENUATOR

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Si5324

The Si5324 has two differential clock outputs. The

signal format of each clock output is independently

programmable to support LVPECL, LVDS, CML, or

CMOS loads. When configured for CMOS, four clock

outputs are available. If not required, the second clock

output can be powered down to minimize power

consumption. In addition, the phase of one output clock

may be adjusted in relation to the phase of the other

output clock. The resolution varies from 800 ps to 2.2 ns

depending on the PLL divider settings. The DSPLLsim

software utility determines the phase offset resolution

for a given combination of input clock and multiplication

ratio. For system-level debugging, a bypass mode is

available which drives the output clock directly from the

input clock, bypassing the internal DSPLL. The device is

in-class PSNR.

3.1. External Reference

An external, high quality 38.88 MHz clock or a low-cost

114.285 MHz 3rd overtone crystal or external reference

is used as part of a fixed-frequency oscillator within the

DSPLL. This external reference is required for the

device to perform jitter attenuation. Specific

recommendations can be found in the Family Reference

Manual.

In digital hold, the DSPLL remains locked and tracks the

external reference. Note that crystals can have

temperature sensitivities.

Due to the low bandwidth capabilities of this part, any

low-frequency wander or instability on the external

reference will transfer to the output clocks. To address

this issue, a stable external reference, TXCO, OCXO, or

thermally-isolated crystal is recommended.

For example, with a 20 ppm oscillator as the reference

on the XA/XB pins, temperature changes cause the

oscillator to change frequency slightly. Although the

Si5324 is locked to its input on CLKIN, it also uses the

XA/XB as a reference.

If there is a need to use a reference oscillator instead of

a crystal, Silicon Labs does not recommend using

MEMS based oscillators. Instead, Silicon Labs

recommends the Si530EB121M109DG, which is a very

low-jitter/wander, LVPECL, 2.5 V crystal oscillator. The

very low loop BW of the Si5324 means that it can be

susceptible to XAXB reference sources that have high

wander. Experience has shown that in spite of having

low jitter, some MEMs oscillators have high wander, and

these devices should be avoided. Contact Silicon Labs

for details.

3.2. Additional Documentation

Consult the Silicon Laboratories Any-Frequency

Precision Clock Family Reference Manual (FRM) for

detailed information about the Si5324. Additional design

support is available from Silicon Laboratories through

your distributor.

Silicon Laboratories offers a PC-based software utility

called DSPLLsim to simplify device configuration,

including frequency planning and loop bandwidth

selection. The FRM and this utility can be downloaded

from http://www.silabs.com/timing.

Rev. 1.0

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