LUCL9218AAR-D AGERE [Agere Systems], LUCL9218AAR-D Datasheet - Page 24

• Manufacturer Part Number: LUCL9218AAR-D
• Description: Low-Cost Line Interface
• Manufacturer: AGERE [Agere Systems]

L9218A/G Low-Cost Line Interface
Applications
ac Design
Example 1: Real Termination (First-Generation Codec) (continued)
The following design equations refer to the circuit in Figure 16. Use these to synthesize real termination imped-
ance.
Termination Impedance:
Z
Receive Gain:
g
g
Transmit Gain:
g
g
Hybrid Balance:
h
To optimize the hybrid balance, the sum of the currents at the VFX input of the codec op amp should be set to 0.
The following expressions assume the test network is the same as the termination impedance:
R
h
24
24
rcv
rcv
tx
tx
bal
bal
T
HB
=
=
=
=
=
= 20log
= 20log
=
------------- -
–
----------
R
V
V
-------------- -
V
R
V
------------- -
------------------------------------------------------------------------------------ -
I
------------------------ -
g
T R
GSX
T6
T R
V
1
T R
Z
X
T R
tx
T
fr
+
R
x
R
-------------- -
=
X
R
V
-------------- -
g
V
RCV
403
---------- -
(continued)
rcv
Z
2R
T3
GSX
T R
----------- -
R
R
T
HB
X
P
+
+
–
(continued)
7.86
R
-------------- -
R
g
---------------------------------- -
1
RCV
GP
tx
+
-------- -
R
R
g
3168
G P
T 3
1
rcv
+
+
------------ -
Z
Z
----------- -
R
T/R
R
T
R C V
T 3
November 2001
Agere Systems Inc.
Data Sheet