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STLC30R80 Datasheet(PDF) 5 Page - STMicroelectronics |
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STLC30R80 Datasheet(HTML) 5 Page - STMicroelectronics |
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5 / 13 page  Concerning AC characteristic the STLC30R80 al- lows to set 2W termination impedance by means of one external scaled impedance that may be com- plex. Two to four wire conversion is provided by an external network. Such network can be avoided in case of application with COMBOII, in this case the two to four wire conversion is implemented inside the COMBOII by means of the programmable Hy- bal filter. When in ACTIVE mode it is also possible to per- form battery reversal in soft mode (with program- mable transition time) without affecting the AC sig- nal transmission. Ringing When ringing mode is selected, by toggling the D2 pin is possible to insert the ringing signal on the line: the ringing frequency is equal to the one applied to the D2 pin. The ringing signal is a bal- anced trapezoidal wave form where the TIP and RING voltages switch continuously between GND and VREG: VREG is obtained directly from VB1 (VREG = VB1 - 1.8V). The slope of the trapezoi- dal wave form is set by the external Crev capaci- tor and it allows to obtain ringing signal with dis- tortion less than 10%: with a fine tuning of this capacitor is possible to obtain distortion value less than 5% (crest factor from 1.25 to 1.35). The VB1 value must be higher enough (~70V) in order to obtain ringing signals with more than 40Vrms. The VB2 battery is used only when the line is in off hook and its value can be reduced (typ. 24V) in order to minimize the power con- sumption. The ring trip detection is performed sensing the variation of the AC line impedance from on-hook (relatively high) to off-hook (relatively low). This particularly ring trip method allows to operate without DC off-set superimposed on the ringing signal and therefore obtaining the maximum pos- sible ring level on the load starting from a given negative battery. It should be noted that such a meted is optimized for operation on short loop applications and may not operate properly in presence of long loop (>500 Ohm). As the ring trip is detected the logic indicator DET is set low and the ringing is automatically discon- nected without waiting for the card controller com- mand (auto ring trip). Ringing with high REN number When ringing high number of REN, for example 5REN, or short loops, it could happen that the line AC current, trigger the ring trip circuit producing false ring trip. If this happens, a proper SW resistor (Rswitch) can be inserted between RLIM and the pin. The effect of this resistor is to improve the AC current capability in Ring mode avoiding false ring trip in presence of high REN numbers (typ. 5REN) and short loop. One side effect of Rswitch is to reduce ring trip sensitivity in presence of long loops; therefore it is recommended to adjust Rswitch properly check- ing the correct behaviour of the device in the two worst-case conditions: - 0 Ω loop, Max REN# - Max loop length, 1 REN The lower is the Rswitch value; the higher is the immunity to false Ring trip, producing as side ef- fect a lower Ring trip sensitivity on long loops. The typical value of Rswitch is shown in the Ex- ternal Components Table (pag.7.13) High Impedance Feeding. As Stand-By, this mode is set in On-Hook condi- tion, with further reduced power consumption. Higher power efficiency turns back a lower immu- nity of the Off-Hook detector to line common mode currents. The DC feeding shows a constant current characteristic (Ilim = 17mA) followed by a resistive range with an equivalent series resis- tance RFEED = 1600 Ω + 2Rp. Thermal protection circuit is still active, preventing the junction temperature, in case of fault condi- tion, to exceed 150°C In High Impedance Feeding most of the circuit is switched off, only the circuit, dedicated to Off- Hook detection, is powered. This allows to reduce 17mA RFEED = 1600Ω +2RP D98TL373 VBAT -0.8V I V Figure d. STLC30R80 DC Characteristic in High Impedance Feeding GND TIP RING dV/dT set by CREV 3V typ. 60V typ. VREG 3V typ. Figure c. Typical ringing wave form. STLC30R80 5/13 |
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Similar Description - STLC30R80 |
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