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Número de pieza

componentes Descripción

Fabricante

74HC7046A

Phase-locked-loop with lock detector

Philips Electronics 

Philips Semiconductors

Phase-locked-loop with lock detector

Product specification

74HC/HCT7046A

SUBJECT

PHASE

COMPARATOR

VCO frequency

with extra

offset

PC1, PC2

DESIGN CONSIDERATIONS

VCO frequency characteristic

With R1 and R2 within the ranges 3 kΩ < R1 < 300 kΩ, 3 kΩ < R2 < 300 kΩ,

the characteristics of the VCO operation will be as shown in Fig. 24.

PC1, PC2

Fig. 24 Frequency characteristic of VCO operating with offset:

fo = centre frequency; 2fL = frequency lock range.

Selection of R1, R2 and C1

Given f0 and fL, determine the value of product R1C1 by using Fig.29.

Calculate foff from the equation foff = fo − 1.6fL.

Obtain the values of C1 and R2 by using Fig.28.

Calculate the value of R1 from the value of C1 and the product R1C1.

December 1990

28

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