STA326 datasheet(2/43 Pages) STMICROELECTRONICS

2 / 43 page

STA326

2/43

Volume loudness, preset volume curves, preset EQ settings, etc. New advanced AM radio inerference re-

duction modes.

The serial audio data input interface accepts all possible formats, including the popular I2S format.

Three channels of DDX® processing are provided. This high quality conversion from PCM audio to DDX's

patented tri-state PWM switching waveform provides over 100dB SNR and dynamic range.

Figure 2.

Figure 3. Channel Signal Flow Diagram through the Digital Core

2.1 EQ Processing

Two channels of input data (re-sampled if necessary) at 96 kHz are provided to the EQ processing block.

In this block, upto 4 user-defined Biquads can be appplied to each of the two channels.

Pre-scaling, dc-blocking high-pass, de-emphasis, bass, and tone control filters can also be applied based

on various configuration parameter settings.

The entire EQ block can be bypassed for all channels simulatneously by setting the DSPB bit to '1'. And

the CxEQBP bits can be used to bypass the EQ functionality on a per channel basis. Figure below shows

the internal signal flow through the EQ block.

2.2 Mix Processing

The Post-EQ Mix block takes the two channel outputs from the EQ block and outputs three channels of

data. By default, Channels 1 and 2 outputs are essentially pass-through of Channels 1 and 2 inputs com-

ing from the EQ block. An additional channel is created as a result of a sum & mix of the two input chan-

nels. See Figure 30. By default, this 3rd channel of data is an equal mix of channel 1 and 2 data. Normally

this third channel will be used as the subwoofer in the 2.1 configuration. An additional filtering stage is

found after the mix block in order to implement crossover filtering. The crossover filters can be automati-

cally configured from the AutoMode Crossover (XO) bits or these filters can be manually programmed for

any type and frequency crossover.

Serial Data

Input,

Channel

Mapping &

Resampling

DDX

Processing

Quad

Half-Bridge

Power Stage

OUT1A

OUT1B

OUT2A

OUT2B

LRCKI

SDI_12

SDA

SCL

PLL

EAPD

BICKI

FAULT

TWARN

Power-Down

System Control

Audio EQ, Mix,

Crossver,

Volume, Limiter

Processing

System Timing

CLK

Channel

Mapping

Re-sampling

Processing

Mix

Volume

Limiter

Interp

DDX

Input

DDX

Output

Crossover

Filter

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