CS2000P-CZZR 参数 Datasheet PDF下载

CS2000-OTP

Delta-Sigma Fractional-N Frequency Synthesizer

Timing Reference

Clock

Phase

Comparator

Internal

Loop Filter

Voltage Controlled

Oscillator

PLL Output

Fractional-N

Divider

Delta-Sigma

Modulator

Digital PLL and Fractional-N Logic

N

Digital Filter

Frequency Reference

Clock

Frequency

Comparator for

Frac-N Generation

Output to Input Ratio for Hybrid mode

Figure 3. Hybrid Analog-Digital PLL

4.2.1

Fractional-N Source Selection for the Frequency Synthesizer

The fractional-N value for the frequency synthesizer can be sourced from either a static ratio or a dynamic

ratio generated from the digital PLL (see

This allows for the selection between operating in the

static ratio based Frequency Synthesizer Mode as a simple frequency synthesizer (for frequency gener-

ation from the Timing Reference Clock) and in the dynamic ratio based Hybrid PLL Mode (for jitter reduc-

tion and clock multiplication). Selection between these two modes can either be made automatically

based on the presence of the Frequency Reference Clock or manually through the mode select pins.

Timing Reference Clock

Fractional-N

Frequency Synthesizer

PLL Output

N

Output to Input Ratio for Synthesizer Mode

Frequency Reference Clock

Digital PLL & Fractional-N Logic

Output to Input ratio for Hybrid Mode

Figure 4. Fractional-N Source Selection Overview

DS758PP1

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