Table 3-4. Audio Pa Status - Motorola ASTRO XTS 5000 Detailed Service Manual

3-26
3.2.3.2 5 V Regulator U505
The 5 V regulator uses UNSW_B+ as its input voltage. The Flipper IC WDI line controls the
regulator's SHUTDOWN pin. The 5 V supply (R503) is used by the Flipper IC U301, audio pre-
amplifier U502, microphone bias circuitry (R531 and R563), Flipper IC protection diodes, bi-
directional voltage translators, battery data-line isolation circuitry, and ESD protection circuitry.
3.2.3.3 1.55 V Regulator
The 1.55 V regulator is made up of the following components: U508, Q503, R598, R507, R508,
R509, R512, R599, C576, C565, C512, C580, and C567 (check the NNTN4717 VOCON board BOM
for part values and placement). This circuit uses VSW1 to bias the regulator while VSW2 sources the
current. This voltage is used by the dual-core processor U401 for its core voltage and clock amplifier.
The 1.55 V regulator is only instantiated on the NNTN4717 VOCON board.
3.2.3.4 Audio Pre-Amplifier U502
The audio pre-amplifier U502 is a single-package, 5-pin, op-amp supplied with 5 volts. This pre-amp
stage provides a fixed gain, which is selected by the components R551 and R537. The input (U502
pin 4) of stage is the EXTOUT pin from the GCAP II IC, while the output (U502 pin 1) of this stage
goes to the audio PA.
3.2.3.5 Audio Power Amplifier U503
The audio power amplifier (PA) U503 consists of two BTL amplifiers, complementary outputs, and
control logic. Each of the amplifiers has a fixed gain—the external audio PA gain is set by
components R553 and R554, while the internal audio PA gain is set by components R549 and R550.
The MODE pin (U503 pin 4) voltage determines the operation of the amplifier. That voltage is
controlled by the Patriot IC GPIO lines AUDIO_PA_EN (to Q505) and AUDIO_MODE_SEL (to
Q506). Table 3-4
AUDIO_PA_EN
0
0
1
1
The SELECT pin (U503 pin 6) is used to switch the audio path between internal and external
speaker. The voltage on that pin is determined by the EXT_SPKR_SEL line from the Patriot IC and
the Q505 transistor. When the voltage at the SELECT pin is high (B+), the audio is routed to the
internal speaker lines. When the voltage at the SELECT pin is low (V_select < 0.5V), the audio is
routed to the external speaker lines.
November 16, 2006
describes how the Patriot IC GPIO lines configure the audio PA.

Table 3-4. Audio PA Status

AUDIO_MODE_SEL
0
1
0
1
Theory of Operation
Audio PA Status MODE Voltage
Standby V_Mode > 7 V
Mute 1.5 V < V_Mode < 6 V
On V_Mode < 0.5 V
On V_Mode < 0.5 V
: VOCON Board
6881094C31-E