MT9043

Data Sheet

10

Zarlink Semiconductor Inc.

For the MT9043, 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 MT9043 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?

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

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.

Since intrinsic jitter is always present, jitter attenuation will appear to be lower for small input jitter signals than for

large ones. Consequently, accurate jitter transfer function measurements are usually made with large input jitter

signals (e.g., 75% of the specified maximum jitter tolerance).

Frequency Accuracy

Frequency accuracy is defined as the absolute tolerance of an output clock signal when it is not locked to an

external reference, but is operating in a free running mode. For the MT9043, the Freerun accuracy is equal to the

Master Clock (OSCi) accuracy.

Capture Range

Also referred to as pull-in range. This is the input frequency range over which the synchronizer must be able to pull

into synchronization. The MT9043 capture range is equal to

(OSCi). For example, a 32 ppm master clock results in a capture range of 198 ppm.

Lock Range

This is the input frequency range over which the synchronizer must be able to maintain synchronization. The lock

range is equal to the capture range for the MT9043.

OutputT1

InputT1

A

–

20

-------





×10

=

OutputT1

20

18

–

20

---------





×10

2.5UI T1

()

==

OutputE1

OutputT1

644ns

()

488ns

()

-------------------

3.3UI T1

()

=

×

=

OutputE1

OutputT1

1UIT1

()

1UIE1

()

----------------------

×

=