ZL30409 Datasheet, PDF (11/32 Pages) Zarlink Semiconductor Inc – T1/E1 System Synchronizer with Stratum 3 Holdover

ZL30409
Data Sheet
ZL30409 Measures of Performance
The following are some synchronizer performance indicators and their corresponding definitions.
Intrinsic Jitter
Intrinsic jitter is the jitter produced by the synchronizing circuit and is measured at its output. It is measured by
applying a reference signal with no jitter to the input of the device, and measuring its output jitter. Intrinsic jitter may
also be measured when the device is in a non-synchronizing mode, such as free running or holdover, by measuring
the output jitter of the device. Intrinsic jitter is usually measured with various bandlimiting filters depending on the
applicable standards. In the ZL30409, the intrinsic Jitter is limited to less than 0.02UI on the 2.048MHz and
1.544MHz clocks.
Jitter Tolerance
Jitter tolerance is a measure of the ability of a PLL to operate properly (i.e., remain in lock and or regain lock in the
presence of large jitter magnitudes at various jitter frequencies) when jitter is applied to its reference. The applied
jitter magnitude and jitter frequency depends on the applicable standards.
Jitter Transfer
Jitter transfer or jitter attenuation refers to the magnitude of jitter at the output of a device for a given amount of jitter
at the input of the device. Input jitter is applied at various amplitudes and frequencies, and output jitter is measured
with various filters depending on the applicable standards. The ZL30409 jitter transfer is determined by the Loop
Filter corner frequency (1.9Hz).
The ZL30409 has twelve outputs with three possible input frequencies (except for 19.44MHz, which is internally
divided to 8KHz) for a total of 36 possible jitter transfer functions. Since all outputs are derived from the same
signal, the jitter transfer values for the four cases, 8kHz to 8kHz, 1.544MHz to 1.544MHz and 2.048MHz to
2.048MHz can be applied to all outputs.
It should be noted that 1UI at 1.544MHz is 644ns, which is not equal to 1UI at 2.048MHz, which is 488ns.
Consequently, a transfer value using different input and output frequencies must be calculated in common units
(e.g., seconds) as shown in the following example.
What is the T1 and E1 output jitter when the T1 input jitter is 20UI (T1 UI Units) and the T1 to T1 jitter attenuation is
18dB?


–-2---A0-- _
OutputT1 = InputT1×10


–--2--1-0--8-_
OutputT1 = 20×10
= 2.5UI(T1)
OutputE1
=
Out
putT1
×
(_{---1---U-----I--T----1----})
(1UIE1)
OutputE1 = OutputT1 × ⁽⁽---64---48---48---nn----ss--⁾⁾-= 3.3UI(T1)
Using the above method, the jitter attenuation can be calculated for all combinations of inputs and outputs based on
the three jitter transfer functions provided.
Note that the resulting jitter transfer functions for all combinations of inputs (8kHz, 1.544MHz, 2.048MHz and
19.44MHz) and outputs (8kHz, 1.544MHz, 2.048MHz, 4.096MHz, 8.192MHz, 16.384MHz, 19.44MHz) for a given
input signal (jitter frequency and jitter amplitude) are the same.
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Zarlink Semiconductor Inc.