Kenwood TK-7180H Service Manual page 23

TK-7180H/7182H
6. Power Supply Circuit
The block diagram of the power supply circuit is shown in
Figure 6.
Power is always supplied from +B to the circuit (5M, +B)
that is always started and the circuits (SB, 8C, 5E, 8T, 8R, 5C,
5R) controlled by the CPU (IC404). When +B is supplied to
the transceiver, Q801, D805 and IC805, regulate the voltage
(5M) which is supplied to the circuit around the CPU. The
CPU starts.
When the CPU detects that the +B voltage is higher than
the voltage prescribed by IC802, the transceiver power (SB)
is turned ON by controlling the SBC signal (Low: transceiver
power OFF, High: transceiver power ON).
Power supply : 10.8~15.7V
22
CIRCUIT DESCRIPTION
F801
Q810
SW
5A
Q807
SW
D804 Q802
DET SW
Q811
SW
CPU
5M
Q801,D805 IC805
Flash memory
REG AVR
EEPROM
Ext-I/O
IC802 IC801
DET DET
CN401
TK-7180H
only
Fig. 6 Power supply circuit
The CPU controls the TXC signal (Low: Transmission sys-
tem power OFF, High: Transmission system power ON) dur-
ing transmission to supply power (8T) to the transmission cir-
cuit. The CPU controls the RXC signal (Low: Reception sys-
tem power OFF, High: Reception system power ON) during
reception to supply power (8R, 5R) to the reception circuit.
When the CPU detects the PSW (Power Switch) signal,
IGN (Ignition Sense) signal or INT signal, it controls the SBC
signal and turns the transceiver power (SB) OFF.
If +B is not provided to the transceiver, power is supplied
to only the RTC IC (IC402) through the secondary battery con-
nected with CN401 to back up the clock.
+B
SB
8C
IC803
AVR
5E
IC807
AVR
SBC
8T
Q803
SW
Q806
SW
8R
Q804
SW
Q808
CPU #17
SW
: RST1
5C
IC804
RTC IC
AVR
5R
Q805
SW
Q809
CPU #24
: INT SW
Final AMP
Audio AMP, PA connector
Panel block, D-sub block
Internal option
Panel block
Internal option
TX-drive
APC block
ANT SW
TXC
IF block
RXC
VCXO, VCO, PLL IC
IF detection IC
DC/DC converter
D/A converter
MIC AMP, AQUA-L
AF block
IF block
RXC