Power Supply Circuit; Lcd; Low Battery Warning; Dsp - Kenwood NX-3220 K Service Manual

2.3.6.3

LCD

The LCD is controlled using parallel interface from MPU /DSP (IC401).
2.3.6.4 Button Detection Circuit
Buttons are detected using MPU/DSP (IC401).
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.
Low battery warning
The red LED blinks during
transmission.
The red LED blinks and the
warning tone beeps while
the PTT switch is pressed.
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
• DTMF encoding/decoding
• MSK encoding/decoding
• 2-tone /5-tone 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, IC651, IC6, IC15), DC/DC converter (IC3), transistor (Q7 through the 0.5A fuse (F2)), transistor
(Q650 through the 0.315A fuse (F650)), 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, MPU/DSP (IC401) operated.
SBC signal becomes High after MPU/DSP (IC401) operates, and IC13 (200C), and IC14 (32C), and IC6 (50C), and Q4 (SB2) are
turned on.
When 5VC signal becomes High, IC651 (50J) operates. When TXC signal becomes High, IC15 (50T) operates. IC15 (50T) is turned
on in transmit mode. Switches are controlled by MPU/DSP (IC401).
When the VOL SW is turned off /PSW signal becomes Low. After detecting /PSW signal, 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 approximately +20VDC.
1-18 (No.RA053<Rev.001>)
Battery condition
The battery voltage is low but the
transceiver is still usable.
The battery voltage is low and the
transceiver is not usable to make
calls.