LUCL8574DP-D AGERE [Agere Systems], LUCL8574DP-D Datasheet - Page 31

• Manufacturer Part Number: LUCL8574DP-D
• Description: L8574D Resistive Subscriber Line Interface Circuit(SLIC), Ring Relay,and Protector(SRP)for Long Loop and TR-57 Applications
• Manufacturer: AGERE [Agere Systems]

Data Sheet
October 1998
ac Design
Design Equations
Using the circuit of Figure 12, the ratio of capacitors C
and to a lesser degree the return loss of the line circuit. Thus, depending on the requirements, C
to be tight tolerance capacitors.
If this is the case, capacitors C
illustrated in Figure 13.
To scale C
by increasing the R
ing the circuit in Figure 13 and by adding resistor R
from XMT to IRP as shown below.
Figure 14. Addition of Resistor R
Then,
Once the gains and complex termination are set, if the
hybrid balance network is identical to the termination
impedance, then the hybrid balance is set by a single
resistor (shown in Figure 12) and is computed as fol-
lows:
Lucent Technologies Inc.
R
----------------------------- -
R
HB
GX1
R
=
VRN
XMT
GX1
IRP
---------------------------- -
K
+
TX
R
S
R
T1
(higher), increase C
GX
K
=
(continued)
Figure 13. Revised ac Interface C
RCV
IRP
------------------------------------ -
R
C
RV1
GX1
B
100
/(R
(continued)
R
XMT
GX1
SC
R
R
R
C
T1
+ R
SC
Relay, and Protector (SRP) for Long Loop and TR-57 Applications
T2
--------- -
400
T
T
1
and C
T
T1
L8574D Resistive Subscriber Line Interface Circuit (SLIC), Ring
R
(and decrease R
GX1
–
C
) ratio by rearrang-
SC
R
-------- -
R
1
R
from XMT to IRP
1
R
RV1
may be combined into a single capacitor with a looser tolerance. This is
R
C
+
T2
T
R
------------------------------
R
RV2
VF
RV1
X
R
IN
12-3427.abF)
RV1
+
R
T
T2
V
SC
and C
SC
F
)
R
O
T
and C
— —
—
R
IRP
The L8574 SLIC is ground referenced. However, a +5 V
only codec, such as T7504, is referenced to +2.5 V. The
L8574 SLIC has sufficient dynamic range to accommo-
date an ac signal from the codec that is referenced to
+2.5 V without clipping distortion. Furthermore, a dc
current will flow between the L8574 SLIC and +5 V only
codec. With the L8574 SLIC, this current will not affect
ac performance, but it does waste power. To avoid
wasted power consumption, blocking capacitors can be
added. Capacitors should be placed to block any path
from any low impedance +2.5 V biased node on the
T7504 codec (or other +5 V only codec) to the SLIC. A
blocking capacitor (C
tion drawing in Figure 14.
After the blocking capacitor C
component values may have to be adjusted slightly to
optimize performance.
The effects of the blocking capacitor are best evaluated
and optimized by circuit simulation. Contact your
Lucent Technologies Microelectronics Group Account
Manager for information on availability of a PSPICE *
model.
* PSPICE is a registered trademark of MicroSim Corporation.
Combined into a Single Capacitor C
R
will affect the (transmit and receive) gain flatness,
C
S
= C
T
+ C
R
XMT
R
B
T2
) has been added in the applica-
R
R
RV1
RV2
B
is added, the above
T
V
F
and C
R
O
S
R
may need
12-3426.a(F).r3
31