LUCL9215AAU-D AGERE [Agere Systems], LUCL9215AAU-D Datasheet - Page 39

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

September 2001
ac Applications
Design Examples
First-Generation Codec ac Interface Network—
Complex Termination
The following reference circuit shows the complete
SLIC schematic for interface to the Agere T7504 first-
generation codec for the German complex termination
impedance. For this example, the ac interface was
designed for a 220
mination and hybrid balance with transmit gain and
receive gain set to 0 dBm. For illustration purposes,
1 Vrms PPM injection was assumed in this example.
This implies the overhead voltage is increased to
7.24 V and no meter pulse rejection is required. Also,
this example illustrates the device using fixed overhead
and current limit.
Complex Termination Impedance Design Example
The gain shaping necessary for a complex termination
impedance may be done by shaping across the AX
amplifier at nodes ITR and VTX.
Complex termination is specified in the form:
To work with this application, convert termination to the
form:
where:
R
R
C´ =
Agere Systems Inc.
1
2
´ = R
´ =
R
------ -
R
---------------------
R
1
2
1
1
R
+ R
(R
+
2
R
1
2
2
+ R
2
C
2
)
R
1
+ (820
(continued)
(continued)
R
2
R
´
1
R
´
C
C´
2
|| 115 nF) complex ter-
5-6396(F)
5-6398(F)
ac Interface Using First-Generation Codec
R
ing to get good gain flatness. These components are a
scaled version of the specified complex termination
impedance.
Note for pure (600
nents R
and is still 4750 .
R
(for complex and resistive terminations) R
varied to give specified transmit gain.
R
tions, the ratio of these resistors sets the receive gain.
For resistive terminations, the ratio of these resistors
sets the return loss characteristic. For complex termi-
nations, the ratio of these resistors sets the low-fre-
quency return loss characteristic.
C
nents provide high-frequency compensation to the
return loss characteristic.
For resistive terminations, these components are not
used and RCVN is connected to ground via a resistor.
R
Set Z
Z
Z
R
R
300 V/A.
R
At dc, C
R
where M is the scale factor.
M =
It can be shown:
R
and
C
TG
T/R
T3
TGS
GX
X
N
HB
1
GX
GX
GX
TGS
´ || R
/R
/R
/R
: sets hybrid balance for all terminations.
/R
= R
must be 4750
= 4750
= M x R
(the specified termination resistance) in the
4750
--------------
T6
N1
= M x R
TG
R
=
RCV
TGS
: with other components set, the transmit gain
/R
2
1
TGS
—Gain Shaping
GX
GS
´ + C´ form.
Short-Loop Sine Wave Ringing SLIC
/R
C
------
N2
M
/C
|| R
and C´ are open.
GP
: for complex terminations, these compo-
and C
GS
1
´
2
: for both complex and resistive termina-
TGS
´
(Z
TG
GS
+ C
): these components give gain shap-
are not used. Resistor R
) resistive terminations, compo-
to set SLIC transconductance to
GS
which is a scaled version of
X
and R
GX
is used
T6
are
39