Datasheet

January 1995 9
Philips Semiconductors Product specification
Phase-locked loop
HEF4046B
MSI
DESIGN INFORMATION
VCO component selection
Recommended range for R1 and R2: 10 kΩ to 1 MΩ; for C1: 50 pF to any practical value.
1. VCO without frequency offset (R2 = ∞).
a) Given f
o
: use f
o
with Fig.7 to determine R1 and C1.
b) Given f
max
: calculate f
o
from f
o
=
1
⁄
2
f
max
; use f
o
with Fig.7 to determine R1 and C1.
2. VCO with frequency offset.
a) Given f
o
and f
L
: calculate f
min
from the equation f
min
=f
o
−f
L
; use f
min
with Fig.8 to determine R2 and C1; calculate
b) Given f
min
and f
max
: use f
min
with Fig.8 to determine R2 and C1; calculate
with Fig.9 to determine R2/R1 to obtain R1.
CHARACTERISTIC USING PHASE COMPARATOR 1 USING PHASE COMPARATOR 2
No signal on SIGN
IN
VCO in PLL system adjusts
to centre frequency (f
o
)
VCO in PLL system adjusts to min.
frequency (f
min
)
Phase angle between
SIGN
IN
and COMP
IN
90° at centre frequency (f
o
),
approaching 0° and 180° at
ends of lock range (2 f
L
)
always 0° in lock
(positive-going edges)
Locks on harmonics of
centre frequency
yes no
Signal input noise
rejection
high low
Lock frequency
range (2 f
L
)
the frequency range of the input signal on which the loop will stay locked if it was
initially in lock; 2 f
L
= full VCO frequency range = f
max
− f
min
Capture frequency
range (2 f
C
)
the frequency range of the input signal on which the loop will lock if it was initially
out of lock
depends on low-pass
filter characteristics; f
C
< f
L
f
C
= f
L
Centre frequency (f
o
) the frequency of the VCO when VCO
IN
at
1
⁄
2
V
DD
f
max
f
min
-----------
from the equation
f
max
f
min
-----------
f
o
f
L
+
f
o
f
L
–
---------------
; use
f
max
f
min
-----------
with Fig. 9 to determine the ratio R2/R1 to obtain R1.=
f
max
f
min
-----------
; use
f
max
f
min
-----------