SI5326C-C-GM Datasheet, PDF (18/72 Pages) Silicon Laboratories – ANY FREQUENCY PRECISION CLOCK MULTIPLIER/JITTER ATTENUATOR

Si5326
4. Functional Description
Xtal or Refclock
CKIN1
CKIN2
÷ N31
÷ N32
Xtal/Refclock
Hitless Switching
Mux
DSPLL^®
÷ N2
÷ N1_HS
÷ N1_LS
÷ N2_LS
CKOUT1
CKOUT2
Loss of Signal/
Frequency Offset
Loss of Lock
Signal Detect
Control
VDD (1.8, 2.5, or 3.3 V)
GND
I²C/SPI Port
Device Interrupt
Rate Select
Clock Select
Skew Control
Figure 6. Functional Block Diagram
The Si5326 is a jitter-attenuating precision clock
multiplier for applications requiring sub 1 ps jitter
performance. The Si5326 accepts two input clocks
ranging from 2 kHz to 710 MHz and generates two
output clocks ranging from 2 kHz to 945 MHz and select
frequencies to 1.4 GHz. The Si5326 can also use its
crystal oscillator as a clock source for frequency
synthesis. The device provides virtually any frequency
translation combination across this operating range.
Independent dividers are available for each input clock
and output clock, so the Si5326 can accept input clocks
at different frequencies and it can generate output
clocks at different frequencies. The Si5326 input clock
frequency and clock multiplication ratio are
programmable through an I²C or SPI interface. Silicon
Laboratories offers a PC-based software utility,
DSPLLsim, that can be used to determine the optimum
PLL divider settings for a given input frequency/clock
multiplication ratio combination that minimizes phase
noise and power consumption. This utility can be
downloaded from http://www.silabs.com/timing.
The Si5326 is based on Silicon Laboratories' 3rd-
generation DSPLL^® technology, which provides any
frequency synthesis and jitter attenuation in a highly
integrated PLL solution that eliminates the need for
external VCXO and loop filter components. The Si5326
PLL loop bandwidth is digitally programmable and
supports a range from 60 Hz to 8.4 kHz. The DSPLLsim
software utility can be used to calculate valid loop
bandwidth settings for a given input clock
frequency/clock multiplication ratio.
The Si5326 supports hitless switching between the two
synchronous input clocks in compliance with GR-253-
CORE that greatly minimizes the propagation of phase
transients to the clock outputs during an input clock
transition (maximum 200 ps phase change). Manual
and automatic revertive and non-revertive input clock
switching options are available. The Si5326 monitors
both input clocks for loss-of-signal (LOS) and provides a
LOS alarm (INT_C1B and C2B) when it detects missing
pulses on either input clock. The device monitors the
lock status of the PLL. The lock detect algorithm works
by continuously monitoring the phase of the input clock
in relation to the phase of the feedback clock. The
Si5326 also monitors frequency offset alarms (FOS),
which indicate if an input clock is within a specified
frequency band relative to the frequency of a reference
clock. Both Stratum 3/3E and SONET Minimum Clock
(SMC) FOS thresholds are supported.The Si5326
provides a digital hold capability that allows the device
to continue generation of a stable output clock when the
selected input reference is lost. During digital hold, the
DSPLL generates an output frequency based on a
historical average frequency that existed for a fixed
amount of time before the error event occurred,
eliminating the effects of phase and frequency
transients that may occur immediately preceding digital
hold.
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Rev. 1.0