ZL30415

Data Sheet

5

Zarlink Semiconductor Inc.

2.2

Frequency/Phase Detector

The Frequency/Phase Detector compares the frequency/phase of the input reference signal with the feedback

signal from the Frequency Divider circuit and provides an error signal equal to the frequency/phase

difference between the two. This error signal is passed to the Loop Filter circuit.

2.3

Lock Indicator

The ZL30415 has a built-in LOCK detector that measures frequency difference between input reference clock C19i

and the VCO frequency. When the VCO frequency is less than ±300 ppm apart from the input reference frequency

then the LOCK output is set high. The LOCK output is pulled low if the frequency difference exceeds ±1000 ppm.

2.4

Loop Filter

The Loop Filter is a low-pass filter. This low-pass filter eliminates high frequency spectral components from a phase

error signal produced by the Phase Detector. This ensures low output jitter that meets network jitter requirements.

The corner frequency of the Loop Filter is configurable with an external capacitor and resistor connected to the LPF

ball and ground as shown in Figure 3.

Figure 3 - Loop Filter Elements

2.5

VCO

The voltage-controlled oscillator (VCO) receives the filtered error signal from the Loop Filter, and based on the

voltage of the error signal generates a primary frequency. The VCO output is connected to the "Frequency Dividers

and Clock Drivers" block that divides VCO frequency and buffer generated clocks.

ZL30415

LPF

Filter

Loop

Frequency

and Phase

Detector

VCO