TK-3148
18
• FFSK
The FFSK input signal from the IF IC is amplifi ed by IC300
(1/2) and goes to pin 5 of IC500. The signal is demodulated
by FFSK demodulator in IC500. The demodulated data goes
to the MCU for processing.
8. Power Supply Circuit
BB is supplied via a 3A fuse from the battery ter-
minal connected to the TX-RX unit. After passing through
the power switch, power supply (SB) is applied to the three
AVRs. IC401 supplies 5V (5M) to the control circuit, and
IC403 supplies 5V (5C) to common circuits. IC402 supplies
to the TX circuit, the RX circuit and common circuits of
needless save mode. During transmission, 5TC becomes
Low and Q405 is turned ON to supply 5V (5T) to the TX
circuit. During reception, 5RC becomes Low and Q404 is
turned ON to supply 5V (5R) to the RX Circuit.
The power supply voltage monitor IC (IC404) monitors
power supply voltage (SB). If the voltage falls (less than 5V),
the VOUT port goes “LOW” level, the MCU INT port also
goes “LOW” level, and the MCU stops.
•
FFSK
来自于中频芯片的 F F S K 输入信号被 I C300(1/2) 放大，然
后进入 IC500 的管脚 5。此信号被 IC500 中的 FFSK 解调器解调。
已解调的数据进入 MCU 执行操作。
8. 电源电路
经由来自于连接到 TX-RX 单元的电池端点的 3A 保险丝提供
电池＋ B。通过电源开关后，电源 (SB) 向 3 个 AVRs 提供电压。
I C401 向控制电路提供 5V (5M ) 电压，I C403 向共用电路提供
5V(5C) 电压。IC402 向 TX 电路，RX 电路和共用电路的保存模
式提供电压。在发送过程中，5T C 变为低电平，且 Q405 接通
并向 TX 电路提供 5V(5T) 电压。在接收过程中，5RC 变为低电
平，且 Q404 接通并向 RX 电路提供 5V(5R) 电压。
电源电压监测 IC(IC404) 监测电源电压 (SB)。如果电压下
降 ( 低于 5V)，则 VOUT 端口变为“低”电平，MCU INT 端口
也变为“低”电平，MCU 停止运行。
IC500
AF IC
LSD IN
HSD IN
IC309
MCU
3
95
DT,CK,CE
IC306
LPF
IC300
AMP
IC303
BPF
IC201
BPF
IC312
5TC
5R
5T
5CNS
Q405
Q404
RF power amp (Q103 and Q106)
D405
ON/OFF
VOL
5C
IC400
R403
C425
R740
IC404
IC403
CE
IC402
CE
IC401
SB
F400
+B
14
10
71
VCC
RESET
INT
IC309
MCU
5RC
Fig. 11 Decode /
图 11 解码
Fig. 12 Power supply circuit /
图 12 电源电路
CIRCUIT DESCRIPTION /
电路说明
