U74HCT7046

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

15 of 16

www.unisonic.com.tw

QW-R502-851.A

APPLICATION INFORMATION(Cont.)

VCO Frequency with Extra Offset

(Phase Comparator: PC1, PC2)

Frequency characteristic:

With R1 and R2 between 3 kΩ and 300 kΩ, the characteristics of the VCO operation will be as shown in Fig.12.

due to R1, C1

0.9V

due to R2, C1

Fig.12 Frequency characteristic of VCO operating with offset:

PC1, PC2

Selection of R1, R2 and C1

Obtain the values of C1 and R2

Calculate the value of R1 from the value of C1 and R1×C1.

Subject

Phase comparator

Design considerations

PLL Conditions with no

PC1

PC2