ADN2811 datasheet(9/20 Pages) AD

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ADN2811

Rev. B | Page 9 of 20

Jitter Tolerance

LOS RESPONSE TIME

Jitter tolerance is defined as the peak-to-peak amplitude of the

sinusoidal jitter applied on the input signal that causes a 1 dB

power penalty. This is a stress test that is intended to ensure no

additional penalty is incurred under the operating conditions

(see Figure 10). Figure 11 shows the typical OC-48 jitter

tolerance performance of the ADN2811.

The LOS response time is the delay between the removal of the

input signal and the indication of loss of signal (LOS) at

SDOUT. The LOS response time of the ADN2811 is 300 ns typ

when the inputs are dc-coupled. In practice, the time constant

of the ac-coupling at the quantizer input determines the LOS

response time.

SLOPE = –20dB/DECADE

JITTER FREQUENCY (Hz)

1.5

0.15

JITTER SPECIFICATIONS

The ADN2811 CDR is designed to achieve the best bit-error-

rate (BER) performance, and has exceeded the jitter generation,

transfer, and tolerance specifications proposed for SONET/SDH

equipment defined in the Telcordia Technologies specification.

Jitter is the dynamic displacement of digital signal edges from

their long-term average positions measured in UI (unit

intervals), where 1 UI = 1 bit period. Jitter on the input data

can cause dynamic phase errors on the recovered clock

sampling edge. Jitter on the recovered clock causes jitter on the

retimed data.

Figure 10. SONET Jitter Tolerance Mask

The following sections briefly summarize the specifications of

jitter generation, transfer, and tolerance in accordance with the

Telcordia document (GR-253-CORE, Issue 3, September 2000)

for the optical interface at the equipment level and the

ADN2811 performance with respect to those specifications.

MODULATION FREQUENCY (Hz)

100k

10M

100

0.1

100

10k

ADN2811

OC-48 SONET MASK

Jitter Generation

Jitter generation specification limits the amount of jitter that

can be generated by the device with no jitter and wander

applied at the input. For OC-48 devices, the band-pass filter has

a 12 kHz high-pass cutoff frequency with a roll-off of

20 dB/decade and a low-pass cutoff frequency of at least

20 MHz. The jitter generated should be less than 0.01 UI rms

and 0.1 UI p-p.

Jitter Transfer

Jitter transfer function is the ratio of the jitter on the output

signal to the jitter applied on the input signal versus the

frequency. This parameter measures the limited amount of jitter

on an input signal that can be transferred to the output signal

(see Figure 9).

SLOPE = –20dB/DECADE

JITTER FREQUENCY (kHz)

0.1

ACCEPTABLE

RANGE

Figure 11. OC-48 Jitter Tolerance Curve

Figure 9. Jitter Transfer Curve

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