Regulator Circuits - Icom IC-725 Service Manual

4-4-2
CPU
(PLL UNIT)
The
CPU
(IC8)
contains
an
8-bit
CMOS
CPU,
16k-byte
ROM
and
256-byte
RAM. The
CPU
controis
operating
frequency,
mode
and the function display, etc.
The
memory
contents are stored
in
the
CPU
using
a
lithium
backup
battery for
more
than 5 years.
The
loom
Cl-V
network system allows
that
the IC-725
can
be remotely
controlled
by a personal
computer
using
an
RS-232C
signal
line.
4-4-3 BIT
CIRCUIT (PLL UNIT)
IC12
is
an
A/D
converter
which
outputs 8-bit serial
data
regarding analog input voltage.
A
voltage, controlled
by
the
[RIT] control,
is
applied to
IC12
pin
4
and
the resulting
serial
data
is
applied
to
the
CPU
matrix
Y4-»
DB4.
4-4-4
KEY MATRIX
YO Y1 Y2
Y3
Y4
Fig.
7
44-5
PARALLEL/SERIAL
CONVERTER
(PLL UNIT)
IC11
is
a
parallel/serial
converter
IC.
Parallel
data from
the
CPU
are converted
into serial
data
to transfer
the
PLL
N-data,
DDS
N-data,
data
for
LCD
driver, etc.
When
the
power
is
turned
ON,
the
CPU
also
outputs
programmable
divider data
and
a
control signal for
universal
ports
to
the
PLL
IC
(IC13).
4-5
REGULATOR
CIRCUITS
Either
8,
5
or
-5
V
DC
are supplied from corresponding
regulator circuits.
8,
5
and
-5
V
DC
are regulated
at
the following circuits using 13.8
V
DC.
(1)
5
V REGULATOR
(PLL UNIT)
5
V
DC
are regulated
by
the three-terminal
voltage
regulator (IC1
0).
(2)
8
V REGULATOR
(MAIN
UNIT)
8
V
DC
are regulated by the three-terminal voltage
regulator (IC14).
(3)
-5 V REGULATOR
(PLL UNIT)
ICG
generates a negative pulse-type voltage by converting
the
DC
input to
AC
voltages (approx. 6.7
kHz) as a
multivibrator.
The
voltage
is
rectified at
D8
and D9,
regulated
by a
Zener
diode (DIO)
and Cl
3,
and
is
then
applied
to
the
MAIN
UNIT.
4
—
7