Texas Instruments TLV320AIC3104 Evaluation Module (EVM) and USB motherboard TLV320AIC3104EVM-K TLV320AIC3104EVM-K 데이터 시트
제품 코드
TLV320AIC3104EVM-K
Digital Audio Data Serial Interface
ADC
+
+
DIN
DOUT
BCLK
WCLK
DINL
DINR
DOUTL
DOUTR
ADC
AGC
AGC
Record Path
Record Path
Effects
Effects
SW-D1
SW-D2
SW-D4
SW-D3
Left-Channel
Analog Inputs
Right-Channel
Analog Inputs
PGA
0 dB–59.5 dB,
0.5-dB Steps
PGA
0 dB–59.5 dB,
0.5-dB Steps
Volume
Control
Volume
Control
DAC
Powered
Down
DAC
Powered
Down
DAC
L
DAC
R
B0173-01
SLAS510C – FEBRUARY 2007 – REVISED DECEMBER 2010
Figure 24. Record-Only Mode With Digital Processing Path Enabled
AUTOMATIC GAIN CONTROL (AGC)
An automatic gain control (AGC) circuit is included with the ADC and can be used to maintain nominally constant
output signal amplitude when recording speech signals (it can be fully disabled if not desired). This circuitry
automatically adjusts the PGA gain as the input signal becomes overly loud or very weak, such as when a
person speaking into a microphone moves closer or farther from the microphone. The AGC algorithm has several
programmable settings, including target level, attack and decay time constants, noise threshold, and maximum
PGA gain applicable, that allow the algorithm to be fine-tuned for any particular application. These AGC features
are explained in following paragraphs, and their operation is illustrated in
output signal amplitude when recording speech signals (it can be fully disabled if not desired). This circuitry
automatically adjusts the PGA gain as the input signal becomes overly loud or very weak, such as when a
person speaking into a microphone moves closer or farther from the microphone. The AGC algorithm has several
programmable settings, including target level, attack and decay time constants, noise threshold, and maximum
PGA gain applicable, that allow the algorithm to be fine-tuned for any particular application. These AGC features
are explained in following paragraphs, and their operation is illustrated in
.The algorithm uses the
absolute average of the signal (which is the average of the absolute value of the signal) as a measure of the
nominal amplitude of the output signal.
nominal amplitude of the output signal.
Note that completely independent AGC circuitry is included with each ADC channel with entirely independent
control over the algorithm from one channel to the next. This is attractive in cases where two microphones are
used in a system, but may have different placement in the end equipment and require different dynamic
performance for optimal system operation.
control over the algorithm from one channel to the next. This is attractive in cases where two microphones are
used in a system, but may have different placement in the end equipment and require different dynamic
performance for optimal system operation.
Target level represents the nominal output level at which the AGC attempts to hold the ADC output signal level.
The TLV320AIC3104 allows programming of eight different target levels, which can be programmed from –5.5
dB to –24 dB relative to a full-scale signal. Because the device reacts to the signal absolute average and not to
peak levels, it is recommended that the target level be set with enough margin to avoid clipping at the occurrence
of loud sounds.
The TLV320AIC3104 allows programming of eight different target levels, which can be programmed from –5.5
dB to –24 dB relative to a full-scale signal. Because the device reacts to the signal absolute average and not to
peak levels, it is recommended that the target level be set with enough margin to avoid clipping at the occurrence
of loud sounds.
Copyright © 2007–2010, Texas Instruments Incorporated
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