Figure 3-31. Rx Audio Path Block Diagram - Motorola APX 1000 Detailed Service Manual

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Theory of Operation

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3.2.5.2 RX Audio path

The RX audio path supports two internal speakers and one external speaker.

The RX internal audio path begins with the digital audio samples being sent from the OMAP1710's

McBSP1 port to the TI AIC33 CODEC through the audio SSI bus. As in the TX audio paths, the

MAKO IC is also used to generate the clock and frame sync for the audio SSI bus. Once the audio

data is received by the TI CODEC, the CODEC proceeds to convert the data to analog and

implements the volume control. The analog signal in the CODEC is then fully differential and gets

sent out to the power amplifier through pins LEFT_LOP and LEFT_LOM. The TI TPA2034D1 Class

D audio power amplifier accepts a fully differential analog input signal and will also drive a

4 Ohm loudspeaker differentially.

The external speaker path is almost identical to the internal speaker path. The digital audio data is

sent from the OMAP1710's McBSP1 port to the TI AIC33 CODEC for digital to analog conversion

and volume control. The external speaker path uses the MAKO IC's class-AB audio power amplifier

to drive 16 Ohm to 28 Ohm external speakers. The input to MAKO IC's audio power amplifier is fully

differential and comes from the TI CODEC's RIGHT_LOP and RIGHT_LOM. The output of the

MAKO IC's audio amplifier is also fully differential and available on pins EXT_SPKR_P and

Low-Pass Filter

20kHz Corner

Figure 3-31. RX Audio Path Block Diagram

Accessory Speaker

~ 16-20 Ohms

Large Internal

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