stlc30r81 STMicroelectronics, stlc30r81 Datasheet - Page 7

• Manufacturer Part Number: stlc30r81
• Description: Integrated Ringing Slic For Short Loop Applications
• Manufacturer: STMicroelectronics

– Selecting Rxin+/Rxin- (first path), the sinusoidal waveform can be applied in differential mode (using
– Selecting Rg+/Rg- (second path), the sinusoidal (or PWM) waveform ringing, can be applied in differ-
Both DC/AC feedback loops are disabled except for the first path (Rxin+/Rxin-) that remains enabled. This func-
tionality will be managed through an "Input Word" that allows the ringing signal, to flow through the line. The
Table 3 shows how to select the proper input word.
Table 3. Control Word
Figure 5. Ringing internal block
In On-Hook condition, Tip and Ring are biased at -VBAT2/2; the input signal is typically amplified at 35dB.
Ring trip detection is performed sensing the variation of the AC line impedance from High (On-Hook) to Low
(Off-Hook). This particular ring trip method, allows to operate without DC offset superimposed on the ring signal
and therefore, obtain the maximum possible load driving capability, from a given negative battery. After Ring/
Trip detection, DET pin is set Low and remains latched keeping the STLC30R81 in Stand-by mode until the op-
erative mode is modified by Input Word.
PWM Ringing Waveform
A pulse-width modulated (PWM) signal may be used to provide the ringing input to Rg inputs. The signal is ap-
plied through a low-pass filter and AC-coupled into Rg+. This approach gives a sine wave output at tip and ring-
ing circuit.
D0
both inputs) or single ended mode (connecting one of the two input pins directly to the GND). This signal
comes from STLC5048 or other Codec
ential mode (using both inputs) or single ended mode (connecting one of the two input pins directly to
the GND). The ring source (codec, waveform generators) can be always active and shared by multiple
lines.
1
1
D1
Control Word
0
0
Rxin+
Rxin-
Rg+
Rg-
D2
0
1
D3
1
1
Rxin+/ Rxin- Input selected
Rg+/Rg- Input selected
D0 D1 D2 D3
OpAmp 1
OpAmp 2
Logic interface
Internal switch
DET
Input Selected Mode
Ring Trip
Ring
Det
Ring
Gain
+
-
STLC30R81
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