LUCL9215AAU-D AGERE [Agere Systems], LUCL9215AAU-D Datasheet - Page 41

• Manufacturer Part Number: LUCL9215AAU-D
• Description: Short-Loop Sine Wave Ringing SLIC
• Manufacturer: AGERE [Agere Systems]

September 2001
ac Applications
Design Examples
Receive Gain
Ratios of R
quency termination and receive gain for the complex
case. In the complex case, additional high-frequency
compensation, via C
return loss characteristic. For resistive termination, C
R
via a resistor.
Determine the receive gain, g
the impedance transformation in a manner similar to
transmit gain.
R
R
Then:
g
and low-frequency termination
Z
Z
ing low frequency (C or C´ is open).
R
50
These two equations are best solved using a computer
spreadsheet.
Next, solve for the high-frequency return loss compen-
sation circuit, C
C
R
There is an input offset voltage associated with nodes
RCVN and RCVP. To minimize the effect of mismatch
of this voltage at T/R, the equivalent resistance to ac
ground at RCVN should be approximately equal to that
at RCVP. Refer to Figure 25 (with dc blocking capaci-
tors). To meet this requirement, R
Agere Systems Inc.
RCV
TER(low)
TER(low)
N1
X
X
P
N
N1
R
(dB) = R
(dB) = 20log g
is the series protection resistor.
, and R
= R
N2
=
is the typical internal feed resistance.
=
----------------------------------------------- -
1
N2
=
is the specified termination impedance assum-
+
------------ -
2400
2R
R
-------------- -
N2
RCV
--------------------------------------------
1
R
2400
------------ -
X (specified[dB])
2R
RCV
+
P
are not used and RCVN is tied to ground
T3
, R
----------- -
R
4
R
P
N
C
2400
GP
, R
+
T3
T3
RCV
G
R
------------- -
R
R
-------------- -
, and R
R
+
N1
R
TGS
TGP
RCV
N
GP
TGP
-------------- -
R
, and R
, R
R
(continued)
(continued)
RCV
T3
+ 20log
N1
–
GP
, and R
1
+ 2R
N2
will set both the low-fre-
RCV
:
P
, taking into account
R
---------- -
600
N2
N2
+ 50
EQ
, is needed for the
= R
GP
|| R
T3
.
N
,
Hybrid Balance
Set the hybrid cancellation via R
R
If a 5 V only codec such as the Agere T7504 is used,
dc blocking capacitors must be added as shown in
Figure 25. This is because the codec is referenced to
2.5 V and the SLIC to ground—with the ac coupling, a
dc bias at T/R is eliminated and power associated with
this bias is not consumed.
Typically, values of 0.1 µF to 0.47 µF capacitors are
used for dc blocking. The addition of blocking capaci-
tors will cause a shift in the return loss and hybrid bal-
ance frequency response toward higher frequencies,
degrading the lower-frequency response. The lower
the value of the blocking capacitor, the more pro-
nounced the effect is, but the cost of the capacitor is
lower. It may be necessary to scale resistor values
higher to compensate for the low-frequency response.
This effect is best evaluated via simulation. A PSPICE
model for the L9215 is available.
Design equation calculations seldom yield standard
component values. Conversion from the calculated
value to standard value may have an effect on the ac
parameters. This effect should be evaluated and opti-
mized via simulation.
HB
=
------------------------------ -
g
Short-Loop Sine Wave Ringing SLIC
RCV
R
X
g
TX
HB
.
41
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