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| 型号： | TLV320ADC3101IRGER |
| 厂商： | TEXAS INSTRUMENTS INC |
| 元件分类： | 消费家电 |
| 英文描述： | SPECIALTY CONSUMER CIRCUIT, PQCC24 |
| 封装： | GREEN, PLASTIC, VQFN-24 |
| 文件页数： | 21/84页 |
| 文件大小： | 1363K |
| 代理商： | TLV320ADC3101IRGER |
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Fine Digital Gain Adjustment
AGC
SLAS553A – NOVEMBER 2008 – REVISED SEPTEMBER 2009...................................................................................................................................... www.ti.com
During volume control changes, the soft-stepping feature is used to avoid audible artifacts. The soft-stepping rate
can be set to either 1 or 2 gain steps per sample. Soft-stepping can also be entirely disabled. This soft-stepping
is configured via page 0 / register 81, bits D1–D0, and is common to soft-stepping control for the analog PGA.
During power-down of an ADC channel, this volume control soft-steps down to –12 dB before powering down.
Due to the soft-stepping control, soon after changing the volume control setting or powering down the ADC
channel, the actual applied gain may be different from the one programmed through the control register. The
TLV320ADC3101 gives feedback to the user through the read-only flags in page 0 / register 36, bit D7 for the left
channel and page 0 / register 36, bit D3 for the right channel.
Additionally, the gain in each of the channels is finely adjustable in steps of 0.1 dB. This is useful when trying to
match the gain between channels. By programming page 0 / register 82, the gain can be adjusted from 0 dB to
–0.4 dB in steps of 0.1 dB. This feature, in combination with the regular digital volume control, allows the gains
through the left and right channels be matched in the range of –0.5 dB to 0.5 dB with a resolution of 0.1 dB.
The TLV320ADC3101 includes automatic gain control (AGC) for ADC recording. AGC can be used to maintain a
nominally constant output level when recording speech. As opposed to manually setting the PGA gain, in the
AGC mode, the 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 to or farther from the microphone. The
AGC algorithm has several programmable parameters, including target gain, attack and decay time constants,
noise threshold, and maximum PGA applicable, that allow the algorithm to be fine-tuned for any particular
application. 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. Because the gain can be changed at the
sample interval time, the AGC algorithm operates at the ADC sample rate.
Target level represents the nominal output level at which the AGC attempts to hold the ADC output signal
level. The TLV320ADC3101 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 TLV320ADC3101 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.
Attack time determines how quickly the AGC circuitry reduces the PGA gain when the output signal level
exceeds the target level due to an increase in input signal level. A wide range of attack-time programmability
is supported in terms of number of samples (i.e., number of ADC sample-frequency clock cycles).
Decay time determines how quickly the PGA gain is increased when the output signal level falls below the
target level due to a reduction in input signal level. A wide range of decay-time programmability is supported
in terms of number of samples (i.e., number of ADC sample-frequency clock cycles).
Noise threshold. If the input signal level falls below the noise threshold, the AGC considers it as silence, and
thus brings down the gain to 0 dB in steps of 0.5 dB every sample period and sets the noise-threshold flag.
The gain stays at 0 dB unless the input signal average rises above the noise threshold setting. This keeps
noise from being amplified in the absence of signal. Noise threshold level in the AGC algorithm is
programmable from –30 dB to –90 dB of full scale. When the AGC noise threshold is set to –70 dB, –80 db,
or –90 dB, the microphone input maximum PGA applicable setting must be greater than or equal to 11.5 dB,
21.5 dB, or 31.5 dB, respectively. This operation includes hysteresis and debounce to prevent the AGC gain
from cycling between high gain and 0 dB when signals are near the noise threshold level. The noise (or
silence) detection feature can be entirely disabled by the user.
Maximum PGA applicable allows the designer to restrict the maximum gain applied by the AGC. This can
be used for limiting PGA gain in situations where environmental noise is greater than the programmed noise
threshold. Microphone input maximum PGA can be programmed from 0 dB to 40 dB in steps of 0.5 dB.
Hysteresis, as the name suggests, determines a window around the noise threshold which must be
exceeded to detect that the recorded signal is indeed either noise or signal. If initially the energy of the
recorded signal is greater than the noise threshold, then the AGC recognizes it as noise only when the
energy of the recorded signal falls below the noise threshold by a value given by hysteresis. Similarly, after
the recorded signal is recognized as noise, for the AGC to recognize it as a signal, its energy must exceed
the noise threshold by a value given by the hysteresis setting. In order to prevent the AGC from jumping
between noise and signal states, (which can happen when the energy of recorded signal is very close to the
noise threshold) a non-zero hysteresis value should be chosen. The hysteresis feature can also be disabled.
Debounce time (noise and signal) determines the hysteresis in time domain for noise detection. The AGC
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Copyright 2008–2009, Texas Instruments Incorporated
Product Folder Link(s) :TLV320ADC3101
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| TLV320ADC3101IRGET | 功能描述:音频模/数转换器 IC 92dB (16B) Low Power Stereo ADC RoHS:否 制造商:Wolfson Microelectronics 转换速率: 分辨率: ADC 输入端数量: 工作电源电压: 最大工作温度: 最小工作温度: 安装风格: 封装 / 箱体: 封装: |
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| TLV320AIC10C | 制造商:TI 制造商全称:Texas Instruments 功能描述:General-Purpose 3V to 5.5V 16-bit 22-KSPS DSP CODEC |
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| TLV320AIC10CPFB | 功能描述:接口—CODEC 16-Bit 22-KSPS DSP Codec RoHS:否 制造商:Texas Instruments 类型: 分辨率: 转换速率:48 kSPs 接口类型:I2C ADC 数量:2 DAC 数量:4 工作电源电压:1.8 V, 2.1 V, 2.3 V to 5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:DSBGA-81 封装:Reel |
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