MT9044AP1 Zarlink Semiconductor, Inc., MT9044AP1 Datasheet - Page 15

• Manufacturer Part Number: MT9044AP1
• Description: Framer: Framer Circuit: T1/E1/OC3 System Synchronizer
• Manufacturer: Zarlink Semiconductor, Inc.

MT9044 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.
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.
For the MT9044, two internal elements determine the jitter attenuation. This includes the internal 1.9Hz low pass
loop filter and the phase slope limiter. The phase slope limiter limits the output phase slope to 5ns/125us.
Therefore, if the input signal exceeds this rate, such as for very large amplitude low frequency input jitter, the
maximum output phase slope will be limited (i.e. attenuated) to 5ns/125us.
The MT9044 has thirteen outputs with three possible input frequencies for a total of 39 possible jitter transfer
functions. However, the data sheet section on AC Electrical Characteristics - Jitter Transfer specifies transfer
values for only three cases, 8kHz to 8kHz, 1.544MHz to 1.544MHz and 2.048MHz to 2.048MHz. Since all outputs
are derived from the same signal, these transfer values apply 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?
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.
OutputT1
OutputT1
OutputE1
OutputE1
=
=
=
=
Zarlink Semiconductor Inc.
InputT1
20
OutputT1
OutputT1
×10
MT9044


–
-------- -
20
×10
18
15
×


×


(
--------------------- -
(
–
------
=
20
1UIE1
(
-------------------
(
1UIT1
A
644ns
488ns


2.5UI T1
)
)
)
)
=
(
3.3UI T1
)
(
)
Data Sheet