Datasheet

AIC3254 Control Software

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4.1.2.1 Adaptive Filtering

The TLV320AIC3254 features double-buffered filter coefficients which allow real-time filtering. The

TLV320AIC3254 features up to six cascaded biquads and a first-order IIR filter per DAC channel in

various signal processing blocks. Note that the TLV320AIC3254 has the potential for a larger amount of

biquad sections if the embedded miniDSP is used for signal processing (see Section 4.1.3.1).

The Parametric Equalizer tab (shown in Figure 9) allows the user to modify the frequency response of the

digital input signal that is fed afterwards into the DAC channels. This application can be useful to fine-tune

the audio frequency response for a particular small speaker and enclosure system combination. The

processing block PRB_P2 (which is used for this application) has one IIR filter and six biquads in cascade

per audio channel. The first biquad (BQ0) is configured as a gain control which provides headroom and

compensation gain to the subsequent biquads in the cascade. Biquads BQ1 to BQ5 are configured for EQ

and/or shelf filters.

The Gain Q (quality) and fc (center frequency) parameters are available for the EQ filters whereas Gain

fc (corner frequency) and Shelf Response are available for the shelf filters. These parameters can be

modified using their corresponding control. Also, by dragging a cursor in the frequency response window,

the gain and fc for each biquad can be modified.

The PRB_P2 biquad coefficients are defined as 1.23, 2s complement format. Coefficients that are equal or

larger than unity must be normalized to comply with such format when converting from decimal format.

This can be achieved by dividing all numerators of a biquad by a scale factor equal to the largest

numerator divided by 2

minus one (if the numerator is equal or larger than unity). Normalization results in

an attenuated version of the same frequency response curve. The scale factor can then be used to

compensate for the attenuation at another unused biquad.

Figure 9. Adaptive Filtering Panel

TLV320AIC3254EVM-K SLAU264A–October 2008–Revised September 2012

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