(No.RA070<Rev.001>)1-15
2.3.6.5
Low Battery Warning
The battery voltage is divided using R65 and R66, it is detected by A/D converter (IC409). When the battery voltage falls below the
voltage set by the Low battery warning adjustment, the red LED blinks to notify the operator that it is time to replace the battery. If the
battery voltage falls even more (approx. 5.8V), a beep sounds and transmission stops.
2.3.6.6
DSP
The DSP circuit consists of a MPU/DSP (IC401) and processes the baseband signal. The DSP operates at 288MHz (MAX) clock, the
I/O section operates at 3.2V/1.8V and the core section operates at 1.2V.
The DSP carries out the following processes:
• 4Level FSK processing
• Analog FM pre-emphasis/de-emphasis
• Vocoder processing between audio codec and modulation/demodulation
• CAI processing, such as error correction encoding
• QT/DQT encoding/decoding
• LTR encoding/decoding
• DTMF encoding/decoding
• MSK encoding/decoding
• Compressor/expander processing
• Voice scrambler processing
• Transmit/receive audio filtering processing
• Microphone amplifier AGC processing
• Audio mute processing
• Modulation level processing
• Active Noise Reduction
• Voice recording/playback processing
• Voice announce processing
2.3.7 Power Supply Circuit
The battery voltage (+B) is provided from battery terminal. The battery voltage passes through the 3.15A fuse (F1), and goes to RF
final amplifier, AVR ICs (IC9, IC17, IC602, IC6, IC15), DC/DC converter (IC3), transistor (Q7 through the 0.5A fuse (F2)), and voltage
detector IC (IC1). Voltage detector (IC1) watches battery voltage. If the battery voltage is enough higher than 5.6V, detector outputs
High. Then, IC9 (31BU) outputs 3.1V, and IC10 (12BU) outputs 1.2V.
When the VOL SW is turned on, SB1 becomes high (battery voltage). DC/DC (IC3) operates if both SB1 and output of detector are
high. IC3 (38M) outputs 3.8V, and IC2 (12M) outputs 1.2V. Then, IC4 (18M) outputs 1.8V. Then, IC5 (32M) outputs 3.2V. Then, IC8
(18BT) outputs 1.8V. Then, IC7 (32BT) outputs 3.2V. Then, IC11 (32A) outputs 3.2V, and IC17 (50A) outputs 5.0V. Then, IC12
(18M_3) outputs 1.8V, and Q7 (53AF) is turned on. Voltage detector (IC403) watches IC3 (38M) output voltage. If the 38M output
voltage is enough higher than 3.5V, detector outputs High.
As a result, the MPU/DSP (IC401) operated.
SBC signal becomes High after the MPU/DSP (IC401) operates, and IC13 (200C), and IC14 (32C), and IC6 (50C), and Q4 (SB2) are
turned on.
When 5UC signal becomes High, IC602 (50U) operates. When TXC signal becomes High, IC15 (50T) operates. IC15 (50T) is turned
on in transmit mode. Switches are controlled by the MPU/DSP (IC401).
When the VOL SW is turned off /PSW signal becomes Low. After detecting /PSW signal, the MPU/DSP (IC401) changes SBC signal
to Low.
38M is fed to IC13 (200C). IC13 (200C) is the DC/DC boost converter. IC13, D10, C50 consist of a voltage quadrupler.
The 200C circuit then outputs approxi20VDC.
Low battery warning
Battery condition
The red LED blinks during
transmission.
The battery voltage is low but the
transceiver is still usable.
The red LED blinks and the
warning tone beeps while
the PTT switch is pressed.
The battery voltage is low and the
transceiver is not usable to make
calls.
