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参数资料
| 型号： | ZL50233/GDG |
| 厂商： | ZARLINK SEMICONDUCTOR INC |
| 元件分类： | 数字传输电路 |
| 英文描述： | DATACOM, ISDN ECHO CANCELLER, PBGA208 |
| 封装： | 17 X 17 MM, 1.30 MM HEIGHT, MO-192, LBGA-208 |
| 文件页数： | 37/38页 |
| 文件大小： | 547K |
| 代理商： | ZL50233/GDG |
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ZL50233
Data Sheet
8
Zarlink Semiconductor Inc.
1.2
Double-Talk Detector
Double-Talk is defined as those periods of time when signal energy is present in both directions simultaneously.
When this happens, it is necessary to disable the filter adaptation to prevent divergence of the Adaptive Filter
coefficients. Note that when double-talk is detected, the adaptation process is halted but the echo canceller
continues to cancel echo using the previous converged echo profile. A double-talk condition exists whenever the
relative signal levels of Rin (Lrin) and Sin (Lsin) meet the following condition:
Lsin > Lrin + 20log10(DTDT)
where DTDT is the Double-Talk Detection Threshold. Lsin and Lrin are signal levels expressed in dBm0.
A different method is used when it is uncertain whether Sin consists of a low level double-talk signal or an echo
return. During these periods, the adaptation process is slowed down but it is not halted. The slow convergence
speed is set using the Slow sub-register in Control Register 4. During slow convergence, the adaptation speed is
reduced by a factor of 2Slow relative to normal convergence for non-zero values of Slow. If Slow equals zero,
adaptation is halted completely.
In the G.168 standard, the echo return loss is expected to be at least 6 dB. This implies that the Double-Talk
Detector Threshold (DTDT) should be set to 0.5 (-6 dB). However, in order to achieve additional guardband, the
DTDT is set internally to 0.5625 (-5 dB).
In some applications the return loss can be higher or lower than 6 dB. The ZL50233 allows the user to change the
detection threshold to suit each application’s need. This threshold can be set by writing the desired threshold value
into the DTDT register.
The DTDT register is 16 bits wide. The register value in hexadecimal can be calculated with the following equation:
DTDT(hex) = hex(DTDT(dec) * 32768)
where 0 < DTDT(dec) < 1
Example:For DTDT = 0.5625 (-5 dB), the
hexadecimal value becomes
hex(
0.5625 * 32768) = 4800hex
1.3
Path Change Detector
Integrated into the ZL50233 is a Path Change Detector. This permits fast reconvergence when a major change
occurs in the echo channel. Subtle changes in the echo channel are also tracked automatically once convergence
is achieved, but at a much slower speed.
The Path Change Detector is activated by setting the PathDet bit in Control Register 3 to “1”. An optional path
clearing feature can be enabled by setting the PathClr bit in Control Register 3 to “1”. With path clearing turned on,
the existing echo channel estimate will also be cleared (i.e. the adaptive filter will be filled with zeroes) upon detection
of a major path change.
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相关代理商/技术参数 |
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| ZL50233QC | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:4 Channel Voice Echo Cancellor |
| ZL50233QCC | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:4 Channel Voice Echo Cancellor |
| ZL50233QCG1 | 制造商:Microsemi Corporation 功能描述:ECHO CANCELLER CHIP 4-CH G.165/G.168/G.711 W/ TONE DETECTION - Trays 制造商:MICROSEMI CONSUMER MEDICAL PRODUCT GROUP 功能描述:IC VOICE ECHO CANCEL 4CH 100LQFP 制造商:Microsemi Corporation 功能描述:IC VOICE ECHO CANCEL 4CH 100LQFP |
| ZL50234 | 制造商:ZARLINK 制造商全称:Zarlink Semiconductor Inc 功能描述:8 Channel Voice Echo Canceller |
| ZL50234/GDC | 制造商:Microsemi Corporation 功能描述:ECHO Canceller Chip 8-CH G.164/G.165/G.168/G.711 With Tone Detection 208-Pin LBGA Tray 制造商:Microsemi Corporation 功能描述:ECHO CANCELLER CHIP 8CH G.164/G.165/G.168/G.711 W/ TONE DETE - Trays 制造商:MICROSEMI CONSUMER MEDICAL PRODUCT GROUP 功能描述:IC VOICE ECHO CANCEL 8CH 208LBGA 制造商:Microsemi Corporation 功能描述:IC VOICE ECHO CANCEL 8CH 208LBGA |
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