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E-STLC3055N View Datasheet(PDF) - STMicroelectronics

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E-STLC3055N Datasheet PDF : 34 Pages
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STLC3055N
Functional description
The STLC3055N feeds the line with a constant current fixed by RLIM (20 mA to 40 mA
range). The on-hook voltage is typically 40 V allowing on-hook transmission; the self
generated Vbat is -50 V typ.
If the loop resistance is very high and the line current cannot reach the programmed
constant current feed value, the STLC3055N behaves like a 40 V voltage source with a
series impedance equal to the protection resistors 2xRp (typ. 2 x 50 Ω). Figure 4 shows the
typical DC characteristic in Active mode.
Figure 4. DC characteristic in active mode
IL
Ilim
(20 to
40mA)
2Rp
VL
10V
Vbat (-50V)
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 5 mA to 9 mA.
Independently on the programmed constant current value, the TIP and RING buffers have a
current source capability limited to 80 mA typ. Moreover the power available at Vbat is
controlled by the DC/DC converter that limits the peak current drawn from the Vpos supply.
The maximum allowed current peak is set by RSENSE resistor.
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 Table 7).
Table 7. Gain set in active mode
Gain set
4 to 2 wire gain
2 to 4 wire gain
Impedance synthesis scale factor
0
0 dB
-6 dB
x 50
1
+6 dB
-12 dB
x 25
Input impedance synthesis: can be real or complex and is set by a scaled (x 50 or
x 25) external ZAC impedance.
Transmit and receive: The AC signal present on the 2W port (TIP and RING pins) is
transferred to the TX output with a -6 dB or -12 dB gain and from the RX input to the
2W port with a 0 dB or +6 dB 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).
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