PBL38614-1 Ver la hoja de datos (PDF) - Ericsson
Número de pieza
componentes Descripción
Fabricante
PBL38614-1 Datasheet PDF : 18 Pages
| |||
PBL 386 14/1
+
TIP
ZL
VTR
ZTR
-
EL
-
+
RING
TIPX
RF
RF
RINGX
RHP
+
-G2-4S
PBL 386 14/1
IL
VTX
IL
ZT
+
VTX
-
ZRX
I L /αRSN
RSN
+
VRX
-
Figure 9. Simplified AC transmission circuit.
Functional Description and Applications
Information Transmission
General
A simplified AC model of the transmission
circuits is shown in figure 9. Circuit analysis
yields:
VTR =
VTX
G2-4S
- IL • 2RF
(1)
α VTX + VRX = IL
ZT ZRX
RSN
(2)
VTR = IL • ZL - EL
(3)
where:
VTX is a ground referenced version
of the ac metallic voltage
between the TIPX and RINGX
terminals.
VTR is the ac metallic voltage
between tip and ring.
EL is the line open circuit ac metallic
voltage.
IL
RF
G2-4S
is the ac metallic current.
is a fuse resistor.
is the SLIC two-wire to four-
wire gain (transmit direction) with
a nominal value of -0.5.
(phase shift 180°.)
ZL is the line impedance.
ZT determines the SLIC TIPX to
RINGX impedance for signal in
the 0 - 20kHz frequency range.
ZRX controls four- to two-wire gain.
VRX
αRSN
RHP
is the analogue ground referenced
receive signal.
is the receive summing node
current to metallic loop current
gain. The nominal value of
αRSN = 400
Internal resistor appprox. 180 kΩ
Two-Wire Impedance
To calculate ZTR, the impedance presented
to the two-wire line by the SLIC including
the fuse resistor RF, let VRX = 0.
From (1) and (2):
α ZTR =
ZT
G RSN • 2-4S
- 2RF
Thus with ZTR, G2-4S, αRSN, and RF known:
α ZT = RSN • G2-4S • (2RF - |ZTR|)
Two-Wire to Four-Wire Gain
From (1) and (2) with VRX = 0:
G2-4
=
VTX
VTR
=
ZT/αRSN
ZT
αRSN • G2-4S
- 2RF
Four-Wire to Two-Wire Gain
From (1), (2) and (3) with EL = 0:
G4-2
=
VTR
VRX
=
ZT •
ZRX
ZL
ZT
αRSN
-
G2-4S
•
(
ZL
+
2RF)
In applications where
2RF - ZT/(αRSN • G2-4S) is chosen to be equal
to ZL, the expression for G4-2 simplifies to:
G4-2 = -
ZT
ZRX
•
1
2 • G2-4S
Four-Wire to Four-Wire Gain
From (1), (2) and (3) with EL = 0:
G4-4
=
VTX
VRX
=
ZZTRX•
G2-4S • ( ZL + 2RF)
ZT
αRSN
-
G2-4S
•
(
ZL
+
2RF)
10
Share Link: 