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CMX866 参数 Datasheet PDF下载

CMX866图片预览
型号: CMX866
PDF下载: 下载PDF文件 查看货源
内容描述: V.22调制解调器双用AT命令 [V.22 bis Modem with AT Commands]
分类和应用: 调制解调器
文件页数/大小: 52 页 / 746 K
品牌: CMLMICRO [ CML MICROCIRCUITS ]
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V.22 bis Modem with AT Commands  
CMX866  
The transmit line signal level is determined by the voltage swing between the TXA and TXAN pins, less  
6dB due to the line termination resistor R13, and less the loss in the line coupling transformer. Allowing  
for 1dB loss in the transformer, then with the DSP Tx Mode Register set for a Tx Level Control gain of  
0dB (S25 register set to 'xxxxx111') the nominal transmit line levels will be:  
AVDD = 3.0V  
-10dBm  
AVDD = 5.0V  
-5.5dBm  
-5.5dBm  
QAM, DPSK and FSK Tx modes (no guard tone)  
Single tone transmit mode  
-10dBm  
DTMF transmit mode  
-6 and -8 dBm  
-1.5 and -3.5 dBm  
For a line impedance of 600W, 0dBm = 775mVrms. See also section 1.7.1.3  
In the receive direction, the signal detection thresholds within the CMX866 are proportional to AVDD and  
are affected by the Rx Gain Control gain setting in the DSP Rx Mode Register (as indicated by the value  
held in the S26 register). The signal level into the CMX866 is affected by the line coupling transformer  
loss and the values of R11 and R12 of Figure 4a.  
Assuming 1dB transformer loss, the Rx Gain Control programmed to 0dB (S26 register set to 'xxxxx111')  
and R12 = 100kW, then for correct operation (see section 1.7.1.3) the value of R11 should be equal to:  
500 / AVDD kW i.e. 160kW at 3.0V, falling to 100kW at 5.0V  
When the RDRVN pin is high impedance (= on-hook = inactive) the auxiliary receive input pin RXBN is  
internally connected to the RXAN pin. This can be used to increase the Rx gain (required for Type 1  
Caller Line Identification reception) by reducing the effective value of R11, as shown in Figures 11 and  
12. When the RDRVN pin is low (= off-hook = active) the RXBN pin is not connected.  
4-Wire Line Interface  
Figure 4b shows an interface for use with a 600W 4-wire line. The line terminations are provided by R10  
and R13, high frequency noise is attenuated by C11 while R11 and R12 set the receive signal level into  
the modem. Transmit and receive line level settings and the value of R11 are as for the 2-wire circuit.  
R10, 13  
R11  
R12  
C3  
C11  
C12  
See Figure 2  
100pF  
33nF  
600W  
See text  
100kW  
Resistors ±5%, Capacitors ±20%  
Figure 4b 4-Wire Line Interface Circuit  
ã 2004 CML Microsystems Plc  
10  
D/866/4