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参数资料
| 型号： | PGA2500IDBG4 |
| 英文描述： | Digitally Controlled Microphone Preamplifier |
| 中文描述： | 数控麦克风前置放大器 |
| 文件页数： | 13/17页 |
| 文件大小： | 206K |
| 代理商： | PGA2500IDBG4 |
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SBOS289A NOVEMBER 2003 REVISED DECEMBER 2003
www.ti.com
13
OPERATION WITH V
COM
IN = +2.5V
When interfacing the analog outputs of the PGA2500 with
audio ADC inputs, the converter will frequently have a
common-mode DC output pin. This pin may be connected
to the V
COM
IN pin of the PGA2500 in order to facilitate a
DC-coupled interface between the two devices. The
common-mode DC voltage level is typically +2.5V,
although some converters may have a slightly lower value,
usually between +2.1V and +2.5V. There are several
issues that must be considered when operating the
PGA2500 in this fashion.
Both the analog input and output pins of the PGA2500 will
be level shifted by the V
COM
IN voltage. The analog outputs
will be shifted to the V
COM
IN level, while the analog inputs
will be shifted to approximately V
COM
IN 0.65V, due to the
offset that normally exists on the input pins. The level
shifting will limit the input and output swing of the
PGA2500, reducing the overall signal-to-noise ratio and
degrading the THD+N performance.
Given V
COM
IN = +2.5V and gains of 10dB through 65dB,
the output swing is limited to less than one-half that
specified in the Electrical Characteristics table. The output
will hard-clip at approximately a diode drop below the VA+
supply rail and a diode drop above analog ground.
Given V
COM
IN = +2.5V and a gain of 0dB, the practical
maximum input or output voltage swing is approximately
1.0Vrms differential. Increasing the signal level much
beyond this point will result in a substantial increase in
distortion.
Plots of THD+N vs Frequency are shown in the Typical
Characteristics section of this datasheet for both
V
COM
IN = 0V and +2.5V. The performance difference can
be seen when comparing the plots. The user needs to
consider whether the difference is acceptable for the end
application.
As a suggested alternative, the PGA2500 analog outputs
may be AC-coupled to the ADC inputs, allowing the
PGA2500 to operate with V
COM
IN = 0V in order to achieve
best performance. The AC-coupling capacitors will affect
the overall low-frequency response of the preamplifier and
converter combination, and the user is advised to choose
a value that best suits the application requirements.
Figure 8 illustrates a typical PGA2500 to audio ADC
interface utilizing AC-coupling. In addition to the coupling
capacitors, a passive RC filter is required as an anti-alias
filter for the converter. The vast majority of audio ADCs are
of the oversampling delta-sigma variety, with a simple
single-pole filter meeting the anti-aliasing requirements for
this type of converter. Providing at least 6dB of attenuation
will also allow the PGA2500 to operate near full signal
swing without overdriving the ADC inputs.
Figure 9 illustrates an application where the V
COM
IN pin of
the PGA2500 is connected to the common-mode DC
output of the audio ADC, with a DC-coupled interface
between the PGA2500 analog outputs and the ADC
analog inputs.
R
R
2R
C
PGA
PGA2500
C
C1
C
C2
V
OUT
+
V
OUT
V
COM
IN
ADC
A/D Converter
(1)
+
+
Serial Data Output
PCM or DSD
Coupling
Capacitors
Attenuation and
AntiAlias Filter
NOTE: (1) PCM1804, PCM4202, or PCM4204.
Figure 8. PGA2500 Analog Output to ADC Analog Input Interface, AC-Coupled
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相关代理商/技术参数 |
参数描述 |
|---|---|
| PGA2500IDBR | 功能描述:传声器前置放大器 0dB & 10dB-65dB in 1dB steps RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
| PGA2500IDBRG4 | 功能描述:传声器前置放大器 0dB & 10dB-65dB in 1dB steps RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
| PGA2505 | 制造商:TI 制造商全称:Texas Instruments 功能描述:Digitally-Controlled MICROPHONE PREAMPLIFIER |
| PGA2505EVM | 功能描述:音频 IC 开发工具 PGA2505 Eval Mod RoHS:否 制造商:Texas Instruments 产品:Evaluation Kits 类型:Audio Amplifiers 工具用于评估:TAS5614L 工作电源电压:12 V to 38 V |
| PGA2505IDB | 功能描述:传声器前置放大器 Dig-Controlled Micro phone Preamp RoHS:否 制造商:Texas Instruments 可用增益调整:Digital control, 65 dB to 0 dB 共模抑制比（最小值）: 输入补偿电压: 最大输入电阻:9200 Ohms 最大工作温度:+ 85 C 封装 / 箱体:SSOP-28 封装:Tube |
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