Input Line Voltage; Regulator (U7); Microprocessor (U5); Rs232 Level Shifter (U8) - Motorola Astro XTS Instruction Manual

Input Line Voltage

5V Regulator (U7)

Microprocessor (U5)

RS232 Level Shifter (U8)

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After approximately three hours, or when the battery voltage becomes
10.3V or the temperature reaches 45°C (whichever occurs first), the
microprocessor will reduce the charge current to the trickle rate and
the LED will turn green. This rate will be maintained until the battery
is removed.
The charger compensates for current consumed by the radio. When the
radio is turned on in the console, the XTVA circuitry senses that the
radio's switched B+ signal is high, and an additional 70mA is added to
battery charging current. During radio transmissions, the radio sends a
TX data message, via SB9600 bus, to the XTVA circuitry, causing an
additional 800mA to be added to the battery charging current.
Note: If a totally discharged battery is placed into the XTVA
console, the radio receiver will begin to function normally
within a few seconds. It is a good practice to wait for about
30 seconds before attempting to transmit when using a
high-power radio, and transmission should be kept to a
minimum for the first few minutes. Low-power radios will
allow normal operation sooner.
Power from the vehicle battery (input line voltage, A+) enters the
console at connector J2, pin 1. The maximum specified A+ voltage is
16.6 Vdc. Zener diodes VR29 and VR70 are transient-voltage
suppressors that clamp incoming transients and provide reverse
supply protection.
The 5-volt regulator (U7) and associated circuitry supply regulated
5 Vdc to the microprocessor (U5) and the level-shifter IC (U8).
Capacitors C39, C89, C40, and C80 form a filter to reduce noise on the
5-volt supply line. The filter circuitry also improves the RF noise
immunity.
The microprocessor (U5) communicates with the portable radio, via
the console connector arm, to the radio side connector, using the
SB9600 data bus. The microprocessor informs the radio of connection
of any XTVA accessories, and monitors and controls the XTVA charger.
Microprocessor U5 enters into a self-check mode whenever:
a. supply voltage is received from the vehicle ignition switch or
(consoles with rev "B" and higher) the radio is turned on, and
b. the radio battery is making connection.
During the self-check mode, the microprocessor internally checks its
memory and internal read-only memory (ROM). Externally, the
microprocessor tests the charger. The red and green LEDs will be
scanned on and off, indicating the status of the XTVA system after self-
check. Refer to the troubleshooting section for the LED states.
RS232 level shifter U8 is used to connect a data terminal to the radio.
It translates signal voltage levels from a data device to transistor-
transistor logic (TTL) levels for interface to the portable radio digital
circuitry.