LUCL8574DP-D AGERE [Agere Systems], LUCL8574DP-D Datasheet - Page 29

• 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
Codec Features and Selection Summary
(continued)
Third-Generation Codecs
This class of devices includes the gains, termination im-
pedance, and hybrid balance—all under microproces-
sor control. Depending on the device, it may or may not
include latches.
In the codec selection, increasing software control and
flexibility are traded for device cost. To help decide, it
may be useful to consider the following:
Design Equations
The following section gives the relevant design equa-
tions to choose component values for any desired gain,
termination, and balance network, assuming a complex
termination is desired. Complex termination will be
specified in one of the two forms shown below.
Lucent Technologies Inc.
Will the application require only one value for each
gain and impedance?
Will the board be used in different countries with dif-
ferent requirements?
Will several versions of the board be built? If so, will
one version of the board be most of the production
volume?
Does the application need only real termination
impedance?
Does the hybrid balance need to be adjusted in the
field?
Figure 11. Equivalent Complex Terminations
R
1
(SERIES FORM)
(continued)
R
C
2
Relay, and Protector (SRP) for Long Loop and TR-57 Applications
L8574D Resistive Subscriber Line Interface Circuit (SLIC), Ring
(PARALLEL FORM)
R
2
´
R
1
´
C´
12-3425(F)
Both forms are equivalent to each other, and it does not
matter which form is specified. The component values
in the interface circuit of Figure 11 are calculated
assuming the parallel form is specified. If the termina-
tion impedance to be synthesized is specified in the
series form, convert it to the parallel form using the
equations below:
Note that if the termination impedance is specified as
pure resistive:
Define the gain constant, K, as follows:
Where,
Where |Z
mination impedance Z
tion assumes that the TLP of the codec is 0 dBm
referenced to 600 .
The following equation applies when referring to
Figure 11:
Where,
T
CR
R
X
Z
= 1000 Hz
X
= 2
T
= desired transmit (or Tip/Ring to PCM)
1
= desired receive (or PCM to Tip/Ring)
R
gain in dB
=
2
gain in dB
Z
K
T
K
| (1 kHz) is the magnitude of the complex ter-
is defined per Figure 11 (series form), and
T
K
0
R
RCV
TX
=
=
-----------------------------------------------------------
2
2
-------------------------------------------------------------------------------------- -
=
=
C
------------------------- -
Z
=
2
2
1
C
R
------
K
T
C
R
1
K
600
+
2
0
R
2
1
1
R
0
10
R
2
=
R
10
kHz
1
2
=
2
T
R
1
Tx/20
------------------------------------------ -
1 2
R
2
=
Rx/20
1
being synthesized. This equa-
2
0 and C = C
+
2
+
= power transfer ratio
2
=
+
R
------------------------------ -
2
R
+
C
1
R
for transmit gain
1
R
------ -
R
2
R
2
2
for receive gain
1
+
+
1
2
R
R
C
1
+
R
+
+
R
2
2
R
2
2
2
R
C
R
------ -
R
2
R
2
2
2
1
2
1
+
–
2
j R
---------------------------------- -
1
=
+
2
2
R
C
2
2
R
2
2
C
2
C
2
2
29