74hct4046a NXP Semiconductors, 74hct4046a Datasheet - Page 27

• Manufacturer Part Number: 74hct4046a
• Description: Phase-locked-loop With Vco
• Manufacturer: NXP Semiconductors

Philips Semiconductors
1997 Nov 25
SUBJECT
PLL frequency
PLL locks on
noise rejection at
AC ripple content
capture range
signal input
when PLL is
locked
Phase-locked-loop with VCO
harmonics at
centre frequency
PHASE
COMPARATOR
PC1, PC2 or PC3
PC1 or PC3
PC2
PC1
PC2 or PC3
PC1
PC3
PC2
DESIGN CONSIDERATIONS
Loop filter component selection
A small capture range (2f
yes
no
high
low
f
f
f
r
r
r
(a) 1 = R3 x C2; (b) amplitude characteristic (c) pole-zero diagram
(a)
= 2f
= f
= f
i
i
, small ripple content at
, large ripple content at
Fig.28 Simple loop filter for PLL with offset; R3 + R4
i
, large ripple content at
Fig. 27 Simple loop filter for PLL without offset; R3 500 .
2 = R4 x C2;
3 = (R3 + R4) x C2
= R3 x C2 (b) amplitude characteristic (c) pole-zero diagram
27
c
) is obtained if
DEMOUT
DEMOUT
DEMOUT
= 180
= 0
= 90
2f
c
74HC/HCT4046A
1
-- - 2 f
Product specification
L
500 .