Radio Power; Introduction To This Section; General; B+ Routing For Vhf/Uhf Transceiver Boards - Motorola ASTRO XTS 3000 R Detailed Service Manual

Radio Power

Introduction to
This Section

General

B+ Routing for
VHF/UHF
Transceiver Boards
This section of the manual provides a detailed circuit description of
the power distribution for an ASTRO Digital XTS 3000 radio.
In the ASTRO XTS 3000 radio, power (B+) is distributed to two boards:
the transceiver board and the controller board. In the case of a secure
model radio, B+ is also supplied to the encryption module.
Power for the radio is provided through a battery supplying a nominal
7.5Vdc directly to the transceiver. The battery is available in the
following forms:
• Nickel-Cadmium, 1525 mAh
• Nickel-Cadmium, 1525 mAh, FM Approved
• Nickel-Metal-Hydride, 1650 mAh
• Nickel-Metal-Hydride, 1650 mAh, FM Approved
B+ from the battery is electrically switched to most of the radio, rather
than routed through the on/off/volume control knob, S1. The
electrical switching of B+ supports a "keep-alive" mode. Under
software control, even when the on/off/volume control knob has been
turned to the "off" position, power remains on until the MCU
completes its power-down, at which time the radio is physically
powered-down.
Refer to Figure 2 and the appropriate schematic diagram.
Raw B+ (7.5V) from the battery (Batt B+) enters the radio on the
transceiver board through a 3-contact connector (J3). From J3 it is
routed through two ferrite beads (E1, E101) on the VHF board, or three
ferrite beads (E1, E101, E106) on the UHF board, to the RF power
amplifier module (U105) and ALC IC (U101). Battery B+ is fused, and
then routed through connector J1, pins 15 and 20, to the controller
board (P201, pins 15 and 20). The B+ supply is routed through the
controller board to the on/off/volume control knob (S1) on the
control top/PTT flex at plug P101. With the mechanical on/off switch
(S1) placed in the "on" position, switched B+ (B+ SENSE) is routed
from the control top flex at connector plug P101, pin 32, and applied
to the controller board at connector jack J101, pin 32. This signal is
also fed to resistive divider R170, R172 on the controller board, so that
the microcontrol unit (U701) can monitor the battery voltage.
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