Datasheet

81
4341H–MP3–10/07
AT8xC51SND2C/MP3B
15. DAC and PA Interface
The AT8xC51SND2C implements a stereo Audio Digital-to-Analog Converter and Audio Power
Amplifier targeted for Li-Ion or Ni-Mh battery powered devices.
Figure 15-1. Audio Interface Block Diagram
15.1 DAC
The Stereo DAC section is a complete high performance, stereo, audio digital-to-analog con-
verter delivering 93 dB Dynamic Range. It comprises a multibit sigma-delta modulator with
dither, continuous time analog filters and analog output drive circuitry. This architecture provides
a high insensitivity to clock jitter. The digital interpolation filter increases the sample rate by a
factor of 8 using 3 linear phase half-band filters cascaded, followed by a first order SINC interpo-
lator with a factor of 8. This filter eliminates the images of baseband audio, remaining only the
image at 64x the input sample rate, which is eliminated by the analog post filter. Optionally, a
dither signal can be added that may reduce eventual noise tones at the output. However, the
use of a multibit sigma-delta modulator already provides extremely low noise tones energy.
Master clock is 128 up to 512 times the input data rate allowing choice of input data rate up to 50
kHz, including standard audio rates of 48, 44.1, 32, 16 and 8 kHz. The DAC section is followed
by a volume and mute control and can be simultaneously played back directly through a Stereo
32Ω Headset pair of drivers. The Stereo 32Ω Headset pair of drivers also includes a mixer of a
LINEL and LINER pair of stereo inputs as well as a differential monaural auxiliary input (line
level).
MP3
I
2
S/PCM
Audio
DSEL
DCLK
SCLK
DOUT
Audio
Decoder
Interface
PA
Audio
DAC
Unit
HSR
HSL
AUXP
AUXN
LINEL
LINER
MONOP
MONON
PAINP
PAINN
HPP
HPN
AUDCDIN
AUDCCLK
AUDCCS
Serial Audio Interface
AUDCDOUT