ADN2811 datasheet(11/20 Pages) AD

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ADN2811

Rev. B | Page 11 of 20

JITTER PEAKING

IN ORDINARY PLL

ADN2811

Z(s)

X(s)

f (kHz)

JITTER

GAIN

(dB)

n psh

d psh

The gain of the loop integrator is small for high jitter

frequencies, so larger phase differences are needed to make the

loop control voltage big enough to tune the range of the phase

shifter. Large phase errors at high jitter frequencies cannot be

tolerated. In this region, the gain of the integrator determines

the jitter accommodation. Since the gain of the loop integrator

declines linearly with frequency, jitter accommodation is lower

with higher jitter frequency. At the highest frequencies, the loop

gain is very small and little tuning of the phase shifter can be

expected. In this case, jitter accommodation is determined by

the eye opening of the input data, the static phase error, and the

residual loop jitter generation. Jitter accommodation is roughly

0.5 UI in this region. The corner frequency between the

declining slope and the flat region is the closed-loop bandwidth

of the delay-locked loop, which is roughly 5 MHz.

Figure 13. Jitter Response vs. Conventional PLL

ADN2811 Datasheet(PDF) 11 Page - Analog Devices