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 53. Audio Interface Block Diagram
MP3
Decoder
Unit
DOUT
DCLK
I2S/PCM
Audio
DSEL
Interface
SCLK
HSR
HSL
AUXP
Audio
DAC
AUDCDIN
AUXN
AUDCDOUT
LINEL
LINER
MONOP
MONON
AUDCCLK
AUDCCS
PAINP
PAINN
Audio
PA
HPP
HPN
DAC
The Stereo DAC section is a complete high performance, stereo, audio digital-to-analog
converter delivering 93 dB Dynamic Range. It comprises a multibit sigma-delta modula-
tor 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 cas-
caded, followed by a first order SINC interpolator 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).
80
AT8xC51SND2C
4341D–MP3–04/05
ATMEL [ ATMEL ]
