Datasheet

3−48
0 1 1 0 0 1 0
48
31
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
48
28
1 1 1 0 0 . 1 0 1
0 0 0
48
1
0 0 0 0 1 . 0 1 0
0 1 0 1 0 1 1 0
0 0 0
48
0
0 0 0 0 0 . 1 1 0
0 0 1 1 1 0 1 0
0 0 0
48
0 0 0 0 0 . 0 0 00 0 0 1 1 0 1 0 1
18
18
18
0
0
0
0
0
Figure 3−30. Logarithmic Number Conversions—Spectrum Analyzer/VU Meter
The time window over which the rms estimate is conducted is programmable via the I
2
C bus (subaddress 0xBB). The
time window for a given set of coefficients is approximately:
t
Window
[*
1
Fs ȏn(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 I
2
C
slave mode.
3.9 Dither
The TAS3103A 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 TAS3103A 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 3−31 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 I
2
C master mode, these dither parameters are set by the EEPROM
content and cannot be subsequently changed.