74HC4046A Datasheet, PDF (26/34 Pages) NXP Semiconductors – Phase-locked-loop with VCO

Philips Semiconductors
Phase-locked-loop with VCO
Product specification
74HC/HCT4046A
SUBJECT
PHASE
COMPARATOR
VCO frequency
with extra
offset
PC1, PC2 or PC3
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.26.
PC1, PC2 or PC3
PLL conditions
PC1
with no signal at
the SIG_IN input
PC2
PC3
Fig.26 Frequency characteristic of VCO operating with offset:
f_o = centre frequency; 2f_L = frequency lock range.
Selection of R1, R2 and C1
Given f_o and f_L, determine the value of product R1C1 by using Fig.31.
Calculate f_off from the equation f_off = f_o  1.6f_L.
Obtain the values of C1 and R2 by using Fig.30.
Calculate the value of R1 from the value of C1 and the product R1C1.
VCO adjusts to f_o with φ_DEMOUT = 90° and V_VCOIN = 1/2 V_CC (see Fig.6).
VCO adjusts to f_o with φ_DEMOUT = −360° and V_VCOIN = min. (see Fig.8).
VCO adjusts to f_o with φ_DEMOUT = −360° and V_VCOIN = min. (see Fig.10).
1997 Nov 25
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