Technics ST-9038 User Manual

i
PART
II PLL SYNTHES]ZER
t'
1-7 Phase
comparator
and low-pass
filter
V1
Programmable
freq
uency
divider output
12.5
KHz
+
L'f
Reference
compar¡son
frequency
12.5
KHz
+VDD
Vcc
c
B
o5
a4
To
VCO
R1
IS
GND
Muting
signal
(To
lF)
(To
AF)
1-7-1
Functions of
phase
detector, charge
pump
and LPF
ln the above-mentioned
circuit, the charge
pump
by
the
phase
detector and C-MOS
is involved
in lC
¡rPD861C,
while
LPF is of discrete.
When the
reference
comparison
frequency
is fed into one of the input sides
of the
phasedetector
by
the sequential
logíc
circuit, and
the output
of the
programmable
frequency divider
is fed into
the
other,
the
phase
or frequency
difference between
the two
frequencies
is
detected,
and its
output ¡s
the logic
value of
"O"
or
"1"
in
accordance
with the
phase
"lead"
and
"lag"
or
the
frequency
differences. The
results
are
shown
in the
following.
(1)
When the
programmable
frequency
divider output
Vr
is
lagging
in
phase
compared
wlth
the
reference
comparison
frequency Rr,
"1"
is
theoutput
at
Dr,
and
"0"
at Ur.
(2)
ln the
reverse case,
"0"
is
the output
at
Dr
,
and
"1"
4t
Ur .
(3)
When both
are
¡dentical in
phase,
the output
at Dr and Ur
is
"1"
(4)
The outputs
of Dr
and Ur will
never be
"0"
4t any t¡me.
Since
the
phase
detector
is
able
to detect the
phase
lead
and
lag but
unable
to convert the
current
into DC
power,
the
charge
pump
of
the
C-MOS
is used to achieve
this.
lt is connected to the
active
low-pass
filter consisting
of a darlington
amplif ier and a
CB
network
which
supplies
the DC output
to the VCO.
Suppose
the
frequency
of the VCO
is
shifted by
+Af
for
some
reason, then Vr leads
in
phase
compared
to
Rr, causing
Dr
to
become
"0".
Then,
Or, channel
P,
turns ON
to
change
C'thus
decreasing
the output
voltage
of the active LPF
and
lowering
the VCO
frequency. Next,
VCO,
shifted by
-Af,
causes
Ur
to
become
"0",
therefore
Or of channel
N turns
ON
causing
the
voltage
-t0*
t
I
o6
a7
*
G
chann
Phase
detector'
N
chan nel
Ç

Technics ST-9038 Specifications

General

Brand	Technics
Model	ST-9038
Category	Tuner
Language	English