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| 型号： | TLV320AIC28IRGZRG4 |
| 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： | 16/85页 |
| 文件大小： | 1053K |
| 代理商： | TLV320AIC28IRGZRG4 |
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TLV320AIC28
SLAS418B FEBRUARY 2004 REVISED MAY 2005
www.ti.com
23
MONO AUDIO ADC
Analog Front End
The analog front end of the audio ADC consists of an analog MUX and a programmable gain amplifier (PGA).
The MUX can connect either of the Headset Input (MICIN_HED), Handset Input (MICIN_HND), AUX1 and
AUX2 signal through the PGA to the ADC for audio recording. The Cell-phone Input (CP_IN) can also be
connected to ADC through a PGA at the same time. This enables recording of conversation during a cell-phone
call. The AIC28 also has an option of choosing MICIN_HED/MICIN_HND and AUX1/AUX2 as differential input
pair. The AIC28 also includes two microphone bias circuits which can source up to 5 mA of current, and are
programmable to a 2 V, 2.5 V or 3.3 V level for Headset and 2 V or 3.3 V level for handset.
Because of the oversampling nature of the audio ADC and the integrated digital decimation filtering,
requirements for analog anti-aliasing filtering are very relaxed. The AIC28 integrates a second order analog
anti-aliasing filter with 20-dB attenuation at 1 MHz. This filter, combined with the digital decimal filter, provides
sufficient anti-aliasing filtering without requiring any external components.
The PGA, for microphone and AUX Inputs, allows analog gain control from 0 dB to 59.5 dB in steps of 0.5 dB.
The PGA gain changes are implemented with an internal soft-stepping. This soft-stepping ensures that volume
control changes occur smoothly with no audible artifacts. Upon reset, the PGA gain defaults to a mute condition,
and upon power down, the PGA soft-steps the volume to mute before shutting down. A read-only flag (D0
control register 04H/Page 2) is set whenever the gain applied by PGA equals the desired value set by the
register. The soft-stepping control can be disabled by programming D15=1 in register 1DH of Page 2. When
soft stepping is enabled and ADC power down register is written, MCLK should be running to ensure that
soft-stepping to mute has completed. MCLK can be shut down once Mic PGA power down flag is set.
The PGA, for Cell phone Input (CP_IN) allows gain control from –34.5 dB to 12 dB in steps of 0.5 dB. The PGA
gain changes are implemented with an internal softstepping. This soft-stepping ensures that volume control
changes occur smoothly with no audible artifacts. Upon reset, the PGA gain defaults to a mute condition, and
upon power down, the PGA soft-steps the volume to mute before shutting down. A readonly flag (D7 control
register 1FH/Page 2) is set whenever the gain applied by PGA equals the desired value set by the register. The
soft-stepping control can be disabled by the programming D12=1 in register 1DH of Page 2. When soft-stepping
is enabled and ADC power down register is written, MCLK should be running to ensure that soft-stepping to
mute has completed. MCLK can be shut down once Cell PGA power down flag is set.
Delta-Sigma ADC
The analog-to-digital converter has a delta-sigma modulator with a 128 times oversampling ratio. The ADC can
support maximum output rate of 53 kHz.
Decimation Filter
The audio ADC includes an integrated digital decimation filter that removes high frequency content and
downsamples the audio data from an initial sampling rate of 128 times Fs to the final output sampling rate of
Fs. The decimation filter provides a linear phase output response with a group delay of 17/Fs. The –3 dB
bandwidth of the decimation filter extends to 0.45 Fs and scales with the sample rate (Fs).
Programmable High Pass Filter
The ADC channel has a programmable high-pass filter whose cutoff frequency can be programmed through
control register. By default the high pass filter is off. The high-pass filter is a first order IIR filter. This filter can
be used to remove the DC component of the input signal and offset of the ADC channel.
Automatic Gain Control (AGC)
The AIC28 includes Automatic gain control (AGC) for Microphone Inputs (MICIN_HED or MICIN_HND) and
Cell-phone input (CP_IN). AGC can be used to maintain nominally constant output signal amplitude when
recording speech signals. 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 gain, attack and decay
time constants, noise threshold, and max 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.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TLV320AIC28RGZ | 制造商:TI 制造商全称:Texas Instruments 功能描述:STEREO AUDIO CODEC WITH INTERGRATED HEADPHONE AND SPEAKER AMPLIFIERS |
| TLV320AIC28RGZR | 制造商:TI 制造商全称:Texas Instruments 功能描述:STEREO AUDIO CODEC WITH INTERGRATED HEADPHONE AND SPEAKER AMPLIFIERS |
| TLV320AIC29 | 制造商:TI 制造商全称:Texas Instruments 功能描述:STEREO AUDIO CODEC WITH INTEGRATED HEADPHONE AND SPEAKER AMPLIFIERS |
| TLV320AIC29_07 | 制造商:TI 制造商全称:Texas Instruments 功能描述:STWREO AUDIO CODEC WITH INTERGRATED HEADPHONE AND SPEAKER AMPLIFIERS |
| TLV320AIC29_08 | 制造商:TI 制造商全称:Texas Instruments 功能描述:STEREO AUDIO CODEC WITH INTEGRATED HEADPHONE AND SPEAKER AMPLIFIERS |
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