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L8576B 参数 Datasheet PDF下载

L8576B图片预览
型号: L8576B
PDF下载: 下载PDF文件 查看货源
内容描述: 双振铃SLIC [Dual Ringing SLIC]
分类和应用:
文件页数/大小: 26 页 / 564 K
品牌: AGERE [ AGERE SYSTEMS ]
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Data Sheet  
May 2001  
L8576B Dual Ringing SLIC  
Functional Description (continued)  
Operating States  
The L8576B device has four operating states:  
Transmit and Receive Interface (continued)  
Talk state—normal battery:  
— Normal talk state.  
— Battery feed is connected to the battery supply  
(VBAT).  
— Both receive and transmit transmission paths are  
powered up.  
— dc loop and instantaneous current limiters are  
powered up and active.  
A second gain setting is provided to accommodate ring  
trip. A switch is built into TG2. In ringing mode, TG1  
and TG2 are internally connected, thus shorting out the  
external gain resistor RGX1. This provides a lower trans-  
mit gain for ringing since ring trip is accomplished by  
monitoring the voltage at DCOUT. This lower gain sets  
DCOUT at the appropriate level to accommodate the  
higher currents of the ring trip.  
— NSTAT reflects the status of the switchhook  
detector.  
— PR is negative with respect to PT.  
The receive interface circuitry couples the differential  
signal on receive inputs RCVP and RCVN to the  
tip/ring drivers.  
Talk state—reverse battery:  
— Normal talk state.  
— Battery feed is connected to the battery supply  
(VBAT).  
Data Interface  
— Both receive and transmit transmission paths are  
powered up.  
— dc loop current limiter is powered up and active.  
— NSTAT reflects the status of the switchhook  
detector.  
A 4-wire parallel interface (B2, RNGNG, NDISC, and  
NSTAT) is provided for each channel to control signals  
to and from the system controller. B2 controls the for-  
ward/reverse battery in normal talk mode while  
RNGNG enables the balanced ringing mode of opera-  
tion, and NDISC performs a disconnect state. NSTAT  
reflects either the loop detector output or the ring trip  
detector output, depending on the mode of the section.  
It is the responsibility of the system controller to recog-  
nize ring trip detection and set RNGNG to a logic 0  
state to terminate ringing. The system controller should  
also use RNGNG to set ringing cadence.  
— PR is positive with respect to PT.  
Ringing state:  
— Normal ringing state.  
— Both receive and transmit transmission paths are  
inactive.  
— Balanced ringing is applied to PR and PT, in  
accordance with B2.  
— Current limiter is set for ringing limit.  
— NSTAT reflects the status of the ring trip detector.  
— Only one channel should be in this state at a time  
to control power dissipation.  
Loop Current Detector  
Each section of the device has an integral loop current  
detector set at a nominal 12 mA of dc current. This is  
used to detect off-hook transitions in the normal talk  
state. When current less than the current threshold  
(including no current) is flowing, NSTAT is at logic 1.  
When loop current exceeds 12 mA, the output NSTAT  
switches to a logic 0. No hysteresis is included.  
Disconnect state:  
— Tip and ring drive amplifiers are powered down.  
— Pins PT and PR are high impedance (>100 k).  
— NSTAT is undefined.  
— PT and PR voltage is undefined.  
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Agere Systems Inc.