ZL30111 参数 Datasheet PDF下载

ZL30111

4.0

Measures of Performance

Data Sheet

The following are some PLL performance indicators and their corresponding definitions.

4.1

Jitter

Timing jitter is defined as the high frequency variation of the clock edges from their ideal positions in time. Wander

is defined as the low-frequency variation of the clock edges from their ideal positions in time. High and low

frequency variation imply phase oscillation frequencies relative to some demarcation frequency. (Often 10 Hz or

20 Hz for DS1 or E1, higher for SONET/SDH clocks.) Jitter parameters given in this data sheet are total timing jitter

numbers, not cycle-to-cycle jitter.

4.2

Jitter Generation (Intrinsic Jitter)

Jitter generation is the measure of the jitter produced by the PLL 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. Jitter is usually

measured with various band limiting filters depending on the applicable standards.

4.3

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.

4.4

Lock Time

This is the time it takes the PLL to frequency lock to the input signal. Phase lock occurs when the input signal and

output signal are aligned in phase with respect to each other within a certain phase distance (not including jitter).

Lock time is affected by many factors which include:

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•

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initial input to output phase difference

initial input to output frequency difference

PLL loop filter bandwidth

The presence of input jitter makes it difficult to define when the PLL is locked as it may not be able to align its output

to the input within the required phase distance, dependent on the PLL bandwidth and the input jitter amplitude and

frequency.

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Zarlink Semiconductor Inc.