Functional description

STLC3055N

12/34

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 Figure 5). 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 5.

TIP/RING typical transition from direct to reverse polarity

Metering pulse injection (Ttx)

The metering pulses circuit consists 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.

The metering pulse is obtained starting from two logic signals:

●

CKTTX: is a square wave at the TTX frequency (12 or 16 kHz) and should be

permanently applied to the CKTTX pin or at least for all the duration of the TTX pulse

(including rising and decay phases).

●

D0: enable the TTX generation circuit and define the TTX pulse duration.

These two signals are processed by a dedicated circuitry integrated on chip that generate

the metering pulse as an amplitude modulated shaped squarewave (SQTTX)

(see Figure 6).

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 shaping by the capacitor CS.

Table 8.

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 (normal polarity)

1

1

1

Active TTX injection (reverse polarity)

GND

TIP

RING

dV/dT set

by CREV

4V typ.

40V typ

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