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STLC3055 Datasheet(PDF) 6 Page - STMicroelectronics |
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STLC3055 Datasheet(HTML) 6 Page - STMicroelectronics |
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6 / 22 page  The line status (on/off hook) is monitored by the SLIC’s supervision circuit. The off-hook threshold can be programmed via the external resistor RTH in the range from 5mA to 9mA. Independently on the programmed constant cur- rent value, the TIP and RING buffers have a cur- rent source capability limited to 70mA typ. Moreover the power available at Vbat is control- led by the DC/DC converter that limits the peak current drawn from the Vpos supply. The maxi- mum allowed current peak is set by the RSENSE resistor and it is typically 900mApk. AC CHARACTERISTICS The SLIC provides the standard SLIC transmis- sion functions: Input impedance synthesis: can be real or complex and is set by a scaled (x50) 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 gain and from the RX in- put to the 2W port with a 0dB gain. 2 to 4 wire conversion: The balance imped- ance can be real or complex, the proper can- cellation is obtained by means of two external impedance ZA and ZB. Once in Active mode (D1=1) the SLIC can oper- ate in different states setting properly D0 and D2 control bits (see also Table 2). Table 2. SLIC states in ACTIVE mode D0 D1 D2 Operating Mode 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.) 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 ex- change their polarities following a ramp transition (see fig.3). The transition time is controlled by an external capacitor CREV. This capacitor is also setting the shape of the ringing trapezoidal wave- form. When the control pins set battery reversal the line polarity is reversed with a proper transition time set via an external capacitor (CREV). 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 har- monic distortion of the output signal. The metering pulse is obtained starting from two logic signals: CKTTX: is a square wave at the TTX fre- quency (12 or 16KHz) and should be perma- nently applied to the CKTTX pin or at least for all the duration of the TTX pulse (including ris- ing and decay phases). D0: enable the TTX generation circuit and de- fine the TTX pulse duration. This two signals are then processed by a dedi- cated circuitry integrated on chip that generate the metering pulse as an amplitude modulated shaped squarewave (SQTTX) (see fig.4). Both the amplitude and the envelope of the squarewave (SQTTX) can be programmed by means of external components. In particular the amplitude is set by the two resistors RLV and the IL Ilim VL Vbat (-50V) 10V 2Rp (20 to 40mA) Figure 2. DC characteristic in ACTIVE mode GND TIP RING dV/dT set by CREV 4V typ. 40V typ ON-HOOK Figure 3. TIP/RING typical transition from Direct to Reverse Polarity STLC3055 6/22 |
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Similar Description - STLC3055 |
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