TAS2521
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SLAS687A –FEBRUARY 2013–REVISED FEBRUARY 2013
5.5.1 Analog Inputs AINL and AINR
AINL (pin 3 or C2) and AINR (pin 4 or B2) are inputs to Mixer P and Mixer M along with the DAC output.
Also AINL and AINR can be configured inputs to HP driver. Page1 / register 12 provides control signals for
determining the signals routed through Mixer P, Mixer M and HP driver. Input of Mixer P can be
attenuated by Page1 / register 24, input of Mixer M can be attenuated by Page1 / register 25 and input of
HP driver can be attenuated by Page1 / register 22. Also AINL and AINR can be configured to a monaural
differential input with use Mixer P and Mixer M by Page1 / register 12 setting.
For more detailed information see the TAS2521 Application Reference Guide (SLAU456).
5.6 Audio DAC and Audio Analog Outputs
The mono audio DAC consists of a digital audio processing block, a digital interpolation filter, a digital
delta-sigma modulator, and an analog reconstruction filter. The high oversampling ratio (normally DOSR is
between 32 and 128) exhibits good dynamic range by ensuring that the quantization noise generated
within the delta-sigma modulator stays outside of the audio frequency band. Audio analog outputs include
mono headphone and lineout and mono class-D speaker outputs. Because the TAS2521 contains a mono
DAC, it inputs the mono data from the left channel, the right channel, or a mix of the left and right
channels as [(L + R) ÷ 2], selected by page 0, register 63, bits D5–D4.
For more detailed information see the TAS2521 Application Reference Guide (SLAU456).
5.6.1 DAC
The TAS2521 mono audio DAC supports data rates from 8 kHz to 192 kHz. The audio channel of the
mono DAC consists of a signal-processing engine with fixed processing blocks, a programmable miniDSP,
a digital interpolation filter, multibit digital delta-sigma modulator, and an analog reconstruction filter. The
DAC is designed to provide enhanced performance at low sampling rates through increased oversampling
and image filtering, thereby keeping quantization noise generated within the delta-sigma modulator and
observed in the signal images strongly suppressed within the audio band to beyond 20 kHz. To handle
multiple input rates and optimize power dissipation and performance, the TAS2521 allows the system
designer to program the oversampling rates over a wide range from 1 to 1024 by configuring page 0,
register 13 and page 0 / register 14. The system designer can choose higher oversampling ratios for lower
input data rates and lower oversampling ratios for higher input data rates.
The TAS2521 DAC channel includes a built-in digital interpolation filter to generate oversampled data for
the delta-sigma modulator. The interpolation filter can be chosen from three different types, depending on
required frequency response, group delay, and sampling rate.
The DAC path of the TAS2521 features many options for signal conditioning and signal routing:
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Digital volume control with a range of -63.5 to +24dB
Mute function
In addition to the standard set of DAC features the TAS2521 also offers the following special features:
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Digital auto mute
Adaptive filter mode
5.6.1.1 DAC Processing Blocks — Overview
The TAS2521 implements signal-processing capabilities and interpolation filtering via processing blocks.
These fixed processing blocks give users the choice of how much and what type of signal processing they
may use and which interpolation filter is applied.
The choices among these processing blocks allows the system designer to balance power conservation
and signal-processing flexibility. Table 5-2 gives an overview of all available processing blocks of the DAC
channel and their properties. The resource-class column gives an approximate indication of power
consumption for the digital (DVDD) supply; however, based on the out-of-band noise spectrum, the analog
power consumption of the drivers (AVDD) may differ.
Copyright © 2013, Texas Instruments Incorporated
Application Overview
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