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© 2012 Microchip Technology Inc. DS01422A-page 1
When designing audio docking stations and
accessories for portable digital audio devices, and
other digital audio sources, designers are constrained
by cost, while trying to deliver the highest-quality audio
playback.
In a typical docking station and device accessory, a
digital audio source that plugs into the unit sends a
serial stereo audio data stream over the dock’s data
transfer interface, such as USB. The dock captures
the data stream while performing other crucial tasks,
and routes the stream to an audio Codec or Digital-
to-Analog Converter (DAC) at a specific sample rate,
as shown in Figure 1.
The captured stereo audio stream then flows through a
serial interface to the codec or DAC. Since there are
many possible sources of digitized audio, and not all of
the sources use the same sampling rate, this serial
interface typically adapts the sampling frequency to the
source, or converts the sampled data stream into a
common data rate. Therefore, one of the challenges in
the design of the docking system or device accessory
is to perform the sample-rate conversion without
degrading the audio quality, and at the lowest cost pos-
sible. To deal with these challenges, designers have
typically used a dedicated sample-rate conversion cir-
cuit and/or a high-end audio DAC that incorporates
complex Phase-Locked Loops (PLLs) to ensure flexible
sample rates for stable communication of the sampled
audio data.
FIGURE 1: TYPICAL AUDIO APPLICATION
Author: Jayanth Murthy Madapura
Microchip Technology Inc.
Left
Headphone/
Speaker
Right
Headphone/
Speaker
Digital
Audio
Source
Serial
Input
Connector
Microcontroller
Microcontroller
(Optional)
Sample Rate
Anti-aliasing
Filter
DAC and
Front Panel
Control
Display,
Audio
Amp
Audio
Amp
AN1422
High-Quality Audio Applications Using the PIC32
Verzeichnis
- ・ Blockdiagramm on Seite 7
- ・ Beschreibung der Funktionen on Seite 13
- ・ Anwendungsbereich on Seite 1
