Dc Power Routing-Transceiver Section; Dc Power Routing-Vocon Section; Table 2-2. Transceiver Voltage Regulators - Motorola ASTRO XTSTM 4000 Detailed Service Manual

2-2
2.2 DC Power Routing–Transceiver Section
NOTE: Refer to
schematics showing the transceiver board DC power routing components.
Contact M1705, the B-plus assembly, connects the battery to the mainboard. Capacitors C20 and
C24 provide protection against momentary breaks at the B-plus connector due to contact bounce
when the radio is dropped.
VHF/ UHF: Components C4, C6 and E101 forms a power-line filter for signal RAWB+, which
supplies battery voltage to the transmitter PA.
Transistor Q1301, controlled by signal FET_ENX from the MAKO IC, turns on XSWB+2, which
supplies to the 5-V linear regulator, U1 and TX_ALC block.
Fuse F901 and filter E1104, C1128 and C1129 supply fused B-plus to the VOCON section. In turn,
the VOCON section supplies VSW1, regulated 3.8 Vdc, from the MAKO (Audio, Power & Accessory
Interface IC) switching regulator to the XCVR. VSW1 supplies to the 3V linear regulators in the
transceiver section. The XCVR regulated power supplies are summarized in
Ref.
Desig.
U1
U2
U3
2.3 DC Power Routing—VOCON Section
NOTE: Refer to
schematics showing the VOCON section DC power routing components.
UNSW_B+, or unswitched B+, is routed to Q1301, Q1302 and the MAKO on the VOCON section.
The ON/OFF circuitry block is made up of Q9906, U9901, U9902, U9918, U9903 and Q9904. The
ON_OFF signal triggers the ON/OFF circuitry block which pulls the MECH_SW pin of the MAKO low,
enabling the routing of SWB+ to the XCVR and VOCON sections and the encryption module. SW B+
and UNSW B+ are also supplied to the encryption module through connector J701.
Transistor Q9906 is also under the control of the microcontroller unit (MCU) via V2_FIL from MAKO.
This allows the MCU detect the pressing of the ON/OFF button and to follow an orderly power-down
sequence when it senses that SWB+ is off. This sense is provided through MECH_SW.
May 28, 2008
Table 8.1, "List of Schematics and Boards Overlays," on page 8-1

Table 2-2. Transceiver Voltage Regulators

IC Output
Name Signal Name
LP2989 V5A
LP3985 V3D
LP3985 V3A
Table 8.1, "List of Schematics and Boards Overlays," on page 8-1
Radio Power: DC Power Routing–Transceiver Section
Description
Regulated 5.0 Vdc
Regulated 3.0 Vdc digital
Regulated 3.0 Vdc analog for synthesizer
for a listing of
Table 2-2.
for a listing of
6871620L01-C