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W681512RG 参数 Datasheet PDF下载

W681512RG图片预览
型号: W681512RG
PDF下载: 下载PDF文件 查看货源
内容描述: 单通道语音频带编解码器 [SINGLE-CHANNEL VOICEBAND CODEC]
分类和应用: 解码器编解码器电信电路
文件页数/大小: 38 页 / 317 K
品牌: WINBOND [ WINBOND ]
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W681512  
as an input when AI+ is tied to VDD and the AI- pin is selected as an input when AI+ is tied to VSS (see  
Table 7.1).  
AI+  
Input Amplifier  
Input  
VDD  
Powered Down  
Powered Up  
AO  
1.2 to VDD-1.2  
VSS  
AI+, AI-  
AI-  
Powered Down  
Table 7.1 Input Amplifier Modes of operation  
When the input amplifier is powered down, the input signal at AO or AI- needs to be referenced to the  
analog ground voltage VAG  
.
The output of the input amplifier is fed through a low-pass filter to prevent aliasing at the switched  
capacitor 3.4 kHz low pass filter. The 3.4 kHz switched capacitor low pass filter prevents aliasing of  
input signals above 4 kHz, due to the sampling at 8 kHz. The output of the 3.4 kHz low pass filter is  
filtered by a high pass filter with a 200 Hz cut-off frequency. The filters are designed according to the  
recommendations in the G.712 ITU-T specification. From the output of the high pass filter the signal is  
digitized. The signal is converted into a compressed 8-bit digital representation with either μ-Law or A-  
Law format. The μ-Law or A-Law format is pin-selectable through the μ/A-Law pin. The compression  
format can be selected according to Table 7.2.  
Format  
μ/A-Law Pin  
VSS  
VDD  
A-Law  
μ-Law  
Table 7.2. Pin-selectable Compression Format  
The digital 8-bit μ-Law or A-Law samples are fed to the PCM interface for serial transmission at the  
data rate supplied by the external BCLKT.  
7.2. Receive Path  
The 8-bit digital input samples for the D-to-A path are serially shifted in by the PCM interface and  
converted to parallel data bits. During every cycle of the frame sync FSR, the parallel data bits are fed  
through the pin-selectable μ-Law or A-Law expander and converted to analog samples. The mode of  
expansion is selected by the μ/A-Law pin as shown in Table 7.2. The analog samples are filtered by a  
low-pass smoothing filter with a 3.4 kHz cut-off frequency, according to the ITU-T G.712 specification.  
A sin(x)/x compensation is integrated with the low pass smoothing filter. The output of this filter is  
buffered to provide the differential receive output signals RO+ and RO-. The RO+ or RO- outputs can  
be externally connected to the PAI pin to provide a differential output with high driving capability at the  
PAO+ and PAO- pins. By using external resistors (see section 11 for examples), various gain settings  
Publication Release Date: April, 2007  
- 9 -  
Revision C14