CMX867 データシートの表示（PDF） - MX-COM Inc

部品番号

コンポーネント説明

メーカー

CMX867

Low Power V.22 Modem

MX-COM Inc  

Low Power V.22 Modem

8

CMX867 Advance Information

Allowing for 1dB loss in the transformer, then with the Tx Mode Register set for a Tx Level Control gain of 0dB

the nominal transmit line levels will be:

DPSK and FSK Tx modes (no guard tone)

Single tone transmit mode

DTMF transmit mode

VDD = 3.0V

-10dBm

-10dBm

-6 and -8 dBm

VDD = 5.0V

-5.5dBm

-5.5dBm

-1.5 and -3.5 dBm

For a line impedance of 600Ω, 0dBm = 775mVRMS. See also Section 6.1.3.

In the receive direction, the signal detection thresholds within the CMX867 are proportional to VDD and are

affected by the Rx Gain Control gain setting in the Rx Mode Register. The signal level into the CMX867 is

affected by the line coupling transformer loss and the values of R11 and R12 of Figure 4.

Assuming 1dB transformer loss, the Rx Gain Control programmed to 0dB and R12 = 100kΩ, then for correct

operation (see Section 6.1.3) the value of R11 should be equal to 500 / VDD kΩ i.e. 160kΩ at 3.0V, falling to

100kΩ at 5.0V

3.2.2 4-Wire Line Interface

Figure 5 shows an interface for use with a 600Ω 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.

1:1

Rx

4-Wire

Line

Tx

C12

R10

RXAFB

R12

R11

C11

RXA

RXA

C3

R13

VBIAS

TXA

-

+

CMX867

TXA

Figure 5: 4-Wireline Interface Circuit

R10, 13 600Ω 1 C3

R11 See text

C11

R12

100kΩ

C12

Resistors ±5%, capacitors ±20%

See Figure 2

100pF

33nF

Table 5: 4-Wireline Interface Circuit External Components

2000 MX-COM, Inc.

www.mxcom.com tel: 800 638 5577 336 744 5050 fax: 336 744 5054

Doc. # 20480219.001

4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA

All trademarks and service marks are held by their respective companies.

Share Link: