5-Volt Regulator U505; Audio Pre-Amplifier U502; Audio Power Amplifier U503; Table 4-4. Audio Pa Status - Motorola ASTRO XTS 5000 Detailed Service Manual

4-18
4.3.3.1.3 Audio Circuitry
A 13-bit CODEC, internal to the GCAP II IC and programmable by the Patriot IC through the SPI bus,
converts microphone audio into a digital bit stream for processing by the DSP. The CODEC also
converts receive audio data that was processed by the DSP into an analog audio signal for
amplification to a speaker. The CODEC interfaces to the DSP through the 4-wire SAP bus. The
520 kHz CODEC clock, generated by the Flipper IC, is on the DCLK pin. The 8 kHz CODEC frame-
sync signal, also generated by the Flipper IC, is on the FSYNC pin. The CODEC transmit data signal
is on the TX pin, while the CODEC receive data signal is on the RX pin. For the CODEC to operate
with those clock and frame sync signals, a 13 MHz clock (R302), generated by the Flipper IC, is
supplied to the GCAP CLK_IN pin.
The GCAP II IC contains internal amplification, filtering, and multiplexing functionality for both
receive and transmit audio. These functions are Patriot IC-programmable through the SPI bus. The
input for the internal microphone audio (R540) is the MICIN_NEG pin, while the input for the external
microphone audio (R566) is the AUX_MIC_NEG pin. The output for the speaker audio is the
EXTOUT pin (C533).

4.3.3.2 5-Volt Regulator U505

The 5-volt regulator uses UNSW_B+ as its input voltage. The Flipper IC WDI line controls the
regulator's SHUTDOWN pin. The 5-volt supply (R503) is used by the Flipper IC U301, audio pre-
amplifier U502, microphone bias circuitry (R531 & R563), Flipper IC protection diodes, bi-directional
voltage translators, battery data line isolation circuitry, and ESD protection circuitry.

4.3.3.3 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 8.9 dB of 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.

4.3.3.4 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 of 21 dB. 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).
IC GPIO lines configure the audio PA.
AUDIO_PA_EN
0
0
1
1
April 15, 2002

Table 4-4. Audio PA Status

AUDIO_MODE_SEL
0
1
0
1
Detailed Theory of Operation
Table 4-4
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
describes how the Patriot
68P81094C31-O