Kenwood NX-800 Service Manual page 34

NX-800
7. Power Supply Circuit
+B is connected to Final amplifi er and DC/DC converter
IC (IC405). IC405 regulates +B voltage to 5.0V (50M). 50M
operates whenever +B is supplied. IC402 (33M), IC408 (33A)
and IC409 (15M) are enabled while the 50M are operating.
33M and 15M provide the power to MCU, DSP, and
Flash memory. At this time MCU starts working. Voltage
detector IC (IC401) watches +B voltage. If +B voltage is
higher than 8.6V, IC401 (/BINT) outputs High. If the /BINT
signal is high, Q404 (SB SW) is turned on by SBC signal
from MCU. (High: SB=ON, Low: SB=OFF). When the SB
is turned on, IC403 (80C), IC404 (50C), IC406 (33C), IC407
(33GPS) and IC410 (150C) start working. Q416 and Q412
are controlled by SBC signal. If the SBC signal becomes
High, Q416 (33A-2) operates and Q412 (50MC SW) are
turned on.
+B
F401
5A
D401
DET
IC405
DC/DC
IC401
DET
34
CIRCUIT DESCRIPTION /
Q404
SB SW
SBC
IC403
AVR
Q401
/OVRB
INV
50MC
Q412
50MC SW
33A
IC408
AVR
33A-2
Q416
SW
SBC
15M
IC409
AVR
33M
IC402
AVR
33BU
Q411
/BINT
33BU SW
IC506
DET
Fig. 8 / 图 8
电路说明
7. 电源电路
+ B 连接至末级放大器和 D C / D C 转换器 I C ( I C405)。I C405
将 + B 电压调整至 5.0V (50M )。提供 + B 时，50M 运行。50M 运
行时，IC402(33M)、IC408(33A) 和 IC409(15M) 启用。
33M 和 15M 对 M C U、D S P 和闪存供电。此时 M C U 开始工作。
电压检测 I C ( I C401) 观测 + B 电压。如果 + B 电压高于 8.6V，
则 IC401(/BINT) 输出高。如果 /BINT 信号高，则 Q404(SB SW)
由 MCU 的 SBC 信号开启。( 高 :SB=ON，低 :SB=OFF)。SB 开启
时，IC403(80C)、IC404(50C)、IC406(33C)、IC407(33GPS) 和
I C410(150C ) 开始工作。Q416 和 Q412 由 S B C 信号控制。如果
SBC 信号变高，Q416(33A-2) 运行，并开启 Q412(50MC SW)。
F501
2A
Q407
80T SW
RS-232C Driver
Q408
80R SW
ASIC (Analog)
IC410
DC/DC
Audio circuit
IC404
AVR
ASIC, DSP core
Q409
ASIC, DSP I/O
50R SW
Flash memory
SRAM, RTC
IC406
CN405
AVR
IC407
AVR
MCU Reset
+B
Final Amp
SB
Audio Amp, Display Block
PA connector
SB
D_Sub 25Pin connector
80C
Internal Option
Display Block
80T
TX circuit
TXC
80R
RX circuit
RXC
150C
Assist, Tune circuit
50C
VCO, Internal Option,
I/O expander, FM IC
50R
RX circuit
RXC
33C
TCXO, PLL
33GPS
Internal Option