CMX867(2000) データシートの表示（PDF） - CML Microsystems Plc

部品番号

コンポーネント説明

一致するリスト

CMX867
(Rev.:2000)

Low Power V.22 Modem

CML Microsystems Plc 

Low Power V.22 Modem

CMX867

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 1.7.1.3

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 4a.

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

operation (see section 1.7.1.3) the value of R11 should be equal to 500 / VDD kΩ i.e. 160kΩ at 3.0V, falling to

100kΩ at 5.0V

4-Wire Line Interface

Figure 4b 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.

R10, 13

R11

R12

600Ω

See text

100kΩ

C3

See Figure 2

C11

100pF

C12

33nF

Resistors ±5%, capacitors ±20%

Figure 4b 4-Wire Line Interface Circuit

© 2000 Consumer Microcircuits Limited

8

D/867/1

Share Link: