AD1953_15 datasheet(12/36 Pages) AD

12 / 36 page

REV. 0

AD1953

–12–

quality of compressed audio. In addition, the main channels

have a stereo widening algorithm that increases the perceived

spread of the stereo image.

Most of the signal processing functions are coded using full 48-bit

double-precision arithmetic. The input word length is 24 bits,

with two extra headroom bits added in the processor to allow

internal gains up to 12 dB without clipping (additional gains can

be accommodated by scaling down the input signal in the first

biquad filter section).

A graphical user interface (GUI) is available for evaluation of

the AD1953 (Figure 3). This GUI controls all of the functions

of the chip in a very straightforward and user-friendly interface.

No code needs to be written to use the GUI to control the chip.

For more information on AD1953 software tools, send an email to

SigmaDSP@analog.com.

SIGNAL PROCESSING

Signal Processing Overview

Figure 2 shows the signal processing flow diagram of the AD1953.

The AD1953 is designed to provide all common signal-processing

functions commonly used in 2.0 or 2.1 playback systems. A

7-biquad equalizer operates on the stereo input signal. The

output of this equalizer is fed to a 2-biquad crossover filter for

the main channels, and the mono sum of the left and right equalizer

outputs is fed to a 3-biquad crossover filter for the Sub channel.

Each of the three channels has independent delay compensa-

tion. There are two high quality compressor/limiters available:

one operating on the left/right outputs and one operating on the

subwoofer channel. The subwoofer output may be blended back

into the left/right outputs for 2.0 playback systems. In this

configuration, the two independent compressor/limiters provide

2-band compression, which significantly improves the sound

HPF/

DE-EMPHASIS

RIGHT

LEFT

DELAY

(0ms–3.7ms)

DELAY

(0ms–3.7ms)

DELAY

(0ms–2.3ms)

INTERPOLATION

DAC

OUT

LEFT

INTERPOLATION

DAC

OUT

RIGHT

1 BIQUAD

FILTER

DELAY

(0ms–3.7ms)

MONO DAC

L/R REINJECTION

LEVEL

SUBWOOFER

OUTPUT

SUB DYNAMICS PROCESSOR

SUB CHANNEL

L/R MIX

EQ AND CROSSOVER FILTERS

L/R DYNAMICS PROCESSOR

LEVEL DETECT,

LOOK-UP TABLE

LEVEL DETECT,

LOOK-UP TABLE

7 BIQUAD

FILTERS

7 BIQUAD

FILTERS

CROSSOVER

(2 FILTERS)

CROSSOVER

(2 FILTERS)

CROSSOVER

(3 FILTERS)

DELAY

(0ms–2.3ms)

HPF/

DE-EMPHASIS

Figure 2. Signal Processing Flow

Figure 3. Graphical User Interface

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