Atmel SAM4L Xplained Pro Evaluation Kit Atmel ATSAM4L-XPRO ATSAM4L-XPRO データシート
製品コード
ATSAM4L-XPRO
876
42023E–SAM–07/2013
ATSAM4L8/L4/L2
32. Audio Bit Stream DAC (ABDACB)
Rev: 1.0.0.0
32.1
Features
•
16 bit digital stereo DAC
•
Oversampling D/A conversion architecture
– Adjustable oversampling ratio
– 3rd order Sigma-Delta D/A converters
•
Digital bitstream output
•
Parallel interface
•
Connects to DMA for background transfer without CPU intervention
•
Supported sampling frequencies
– 8000Hz, 11025Hz, 12000Hz, 16000Hz, 22050Hz, 24000Hz, 32000Hz, 44100Hz, and 48000Hz
•
Supported data formats
– 32-, 24-, 20-, 18-, 16-, and 8-bit stereo format
– 16- and 8-bit compact stereo format, with left and right sample packed in the same word to
reduce data transfers
•
Common mode offset control
•
Volume control
32.2
Overview
The Audio Bitstream DAC (ABDACB) converts a 16-bit sample value to a digital bitstream with
an average value proportional to the sample value. Two channels are supported making the
Audio Bitstream DAC particularly suitable for stereo audio. Each channel has a pair of comple-
mentary digital outputs, DAC and DACN, which can be connected to an external high input
impedance amplifier.
an average value proportional to the sample value. Two channels are supported making the
Audio Bitstream DAC particularly suitable for stereo audio. Each channel has a pair of comple-
mentary digital outputs, DAC and DACN, which can be connected to an external high input
impedance amplifier.
The Audio Bitstream DAC is made up of several signal processing blocks and a 3rd order Sigma
Delta D/A converter for each channel. The Sigma Delta modulator converts the parallel data to a
bitstream, while the signal processing blocks perform volume control, offset control, upsampling,
and filtering to compensate for the upsampling process. The upsampling is performed by a Cas-
caded Integrator-Comb (CIC) filter, and the compensation filter is a Finite Impulse Response
(FIR) CIC compensation filter.
Delta D/A converter for each channel. The Sigma Delta modulator converts the parallel data to a
bitstream, while the signal processing blocks perform volume control, offset control, upsampling,
and filtering to compensate for the upsampling process. The upsampling is performed by a Cas-
caded Integrator-Comb (CIC) filter, and the compensation filter is a Finite Impulse Response
(FIR) CIC compensation filter.
32.3
Block Diagram
Figure 32-1. ABDACB Block Diagram
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Sync
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filt
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CIC
Comb
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CI
C In
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grat
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sec
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C lock
divider
Sigm a D elta
M odulator
M odulator
Sigm a D elta
M odulator
M odulator
clk_abdacb
gclk
Signal processing
(before up-sam pling)
C LK
D AC [0]
D A C N [0]
D A C [1]
D A C N [1]
PB