Icom IC-725 - Regulator Circuits

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