参数资料
型号: TLV320AIC29IRGZ
厂商: TEXAS INSTRUMENTS INC
元件分类: 消费家电
英文描述: SPECIALTY CONSUMER CIRCUIT, PQCC48
封装: 7 X 7 MM, GREEN, PLASTIC, QFN-48
文件页数: 18/87页
文件大小: 1049K
代理商: TLV320AIC29IRGZ
TLV320AIC29
SLAS494B DECEMBER 2005 REVISED OCTOBER 2007
www.ti.com
25
Target gain represents the nominal output level at which the AGC attempts to hold the ADC output signal level.
The AIC29 allows programming of eight different target gains, which can be programmed from –5.5 dB to –24
dB relative to a full-scale signal. Since the AIC29 reacts to the signal absolute average and not to peak levels,
it is recommended that the target gain be set with enough margin to avoid clipping at the occurrence of loud
sounds.
Attack time determines how quickly the AGC circuitry reduces the PGA gain when the input signal is too loud.
It can be varied from 8 ms to 20 ms.
Decay time determines how quickly the PGA gain is increased when the input signal is too low. It can be varied
in the range from 100 ms to 500 ms.
Noise threshold is the minimum amplitude for the input signal that the AGC considers as a valid signal. If the
average amplitude of the incoming signal falls below this value, the AGC considers it as silence and brings down
the gain to 0 dB in steps of 0.5 dB for every FS. This will also set the noise threshold flag. The gain stays at
0 dB until the average amplitude of the input signal rises above the noise threshold value. This ensures that
noise does not get amplified in the absence of a valid input speech signal. Noise threshold level is programmable
from 30dB to 90 dB for microphone input, and from 30 dB to 60 dB for cell-phone input. When AGC Noise
Threshold is set to 70 dB, 80 dB, or 90 dB, the microphone input Max PGA applicable setting must be greater
than or equal to 11.5 dB, 21.5 dB, or 31.5 dB respectively. This operation includes debounce and hysteresis
to avoid the AGC gain from cycling between high gain and 0 dB when the signal amplitude is near the noise
threshold level. When the noise threshold flag is set, status of gain applied by AGC and saturation flag should
be ignored.
Maximum input gain applicable allows user to restrict maximum gain applied by the AGC. This can be used
for limiting PGA gain in situations where environment noise is greater than programmed noise threshold.
Microphone input Max PGA can be programmed from 0 dB to 59.5 dB in steps of 0.5 dB. Cell-phone input Max
PGA can be programmed from 34.5 dB to 0.5 dB in steps of 0.5 dB, as well as +12 dB.
See Table 1 for various AGC programming options. AGC can be used only if microphone input or Cell-phone
input is routed to the ADC channel. When both microphone input and Cell-phone input are connected to the
ADC, AGC is automatically disabled.
Decay Time
Target
Gain
Input
Signal
Output
Signal
AGC
Gain
Attack
Time
Figure 19. AGC Characteristics
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TLV320AIC3107IYZFR 2 CHANNEL, AUDIO AMPLIFIER, BGA42
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