TAS3103 datasheet(107/146 Pages) TI

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3−47

0 1 1 0 0 1 0

1 1 1 1 1 . 1 0 0

48-Bit RMS Estimate

Spectrum Analyzer

and

VU Meter Output

0 0 0 0 1 1 0 1 0 1

1 1 1 0 0 . 1 0 1

0 0 0

0 0 0 0 1 . 0 1 0

0 1 0 1 0 1 1 0

0 0 0

0 0 0 0 0 . 1 1 0

0 0 1 1 1 0 1 0

0 0 0

0 0 0 0 0 . 0 0 0

0 0 0 1 1 0 1 0 1

Figure 3−28. Logarithmic Number Conversions—Spectrum Analyzer/VU Meter

The time window over which the rms estimate is conducted is programmable via the I2C bus (subaddress 0xBB). The

time window for a given set of coefficients is approximately:

Window [*

n(1

* asa)

Where FS is the audio sample rate and asa is a 5.23 format number. The variable asa (and 1 – asa) must be kept

within the range of greater than zero and less than one. The time constant programmed applies to all 10 rms estimate

blocks.

CAUTION: The spectrum analyzer and VU meter functions are only accessible in the I2C

slave mode.

3.9

Dither

The TAS3103 provides a dither block for adding triangular or quadratic (sum of two uncorrelated triangular

distributions) distributed noise to the processed audio data stream prior to routing to the output serial audio port

(SAP). Each of the three monaural channels in the TAS3103 has its own dedicated dither data stream that is

statistically independent from the dither data streams used by the other two monaural channels. The statistical

distribution of the dither data stream, triangular or quadratic, is selectable, but the selection made applies to the dither

data streams for all three monaural channels. Each monaural channel is also assigned a mixer for adjusting the level

at which the dither data stream is inserted into the audio data stream.

Figure 3−29 is a detailed block diagram of the dither block. Five subaddresses are used to fully configure the dither

blocks and the associated channel mixers. In the I2C master mode, these dither parameters are set by the EEPROM

content and cannot be subsequently changed.

TAS3103 Datasheet(PDF) 107 Page - Texas Instruments