STLC3075(2005) Ver la hoja de datos (PDF) - STMicroelectronics

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STLC3075
(Rev.:2005)

INTEGRATED POTS INTERFACE FOR HOME ACCESS GATEWAY AND WLL

STMicroelectronics 

STLC3075

3.2.3.2 AC Characteristics

The SLIC provides the standard SLIC transmission functions:

Once in active mode the SLIC can operate with two different Tx, Rx Gain. Setting properly by the Gain set

control bit (see table7).

Table 7. Gain Set in Active Mode

Gain set

4 to 2 wire Gain

2 to 4 wire Gain

Impedance Synthesis Scale Factor

0

0dB

-6dB

x 50

1

+6dB

-12dB

x 25

■ Input impedance synthesis: can be real or complex and is set by a scaled (x50 or x25) external ZAC

impedance.

■ Transmit and receive: The AC signal present on the 2W port (TIP/RING) is transferred to the TX output

with a -6dB or -12dB gain and from the RX input to the 2W port with a 0dB or +6dB gain.

■ 2 to 4 wire conversion: The balance impedance can be real or complex, the proper cancellation is

obtained by means of two external impedance ZA and ZB

Once in Active mode (D1=1) the SLIC can operate in different states setting properly D0 and D2 control

bits (see also Table 8).

Table 8. SLIC states in ACTIVE mode

D0

D1

D2

0

1

0

Active Normal Polarity

0

1

1

Active Reverse Polarity

1

1

0

Active TTX injection (N.P.)

1

1

1

Active TTX injection (R.P.)

Operating Mode

3.2.3.3 Polarity Reversal

The D2 bit controls the line polarity, the transition between the two polarities is performed in a "soft" way.

This means that the TIP and RING wire exchange their polarities following a ramp transition (see fig. 6).

The transition time is controlled by an external capacitor CREV. This capacitor is also setting the shape

of the ringing trapezoidal waveform. When the control pins set battery reversal the line polarity is reversed

with a proper transition time set via an external capacitor (CREV).

Figure 6. TIP/RING typical transition from Direct to Reverse Polarity

GND

TIP

4V typ.

40V typ

ON-HOOK

dV/dT set

by CREV

RING

3.2.3.4 Metering Pulse Injection (TTX)

The metering pulses circuit consist of a burst shaping generator that gives a square wave shaped and a

low pass filter to reduce the harmonic distortion of the output signal.

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