LUCL8576BP-D AGERE [Agere Systems], LUCL8576BP-D Datasheet - Page 21

• Manufacturer Part Number: LUCL8576BP-D
• Description: Dual Ringing SLIC
• Manufacturer: AGERE [Agere Systems]

May 2001
Applications
ac Design
Example 2, Complex Termination
The gain shaping required of a complex termination
impedance can be synthesized using the internal AX
amplifier. The following discussion and equations
present a method for selecting proper component val-
ues for the SLIC/codec interface when using a complex
termination.
Complex termination is usually of the form:
To work with this application, convert termination to the
form:
where:
R
R
C´ =
For the following discussion, refer to Figure 21.
R
shaping to get good gain flatness. These components
are a scaled version of the specified complex termina-
tion impedance. Note for pure (600
nations, components R
Resistor R
bination of R
Agere Systems Inc.
1
2
TGP
´ = R
´ =
/R
R
------ -
R
---------------------
R
TGS
1
1
2
1
R
+ R
+
(R
2
/C
TGP
R
1
2
TGS
2
GX1
(continued)
+ R
is used and is the series resistance com-
2
C
(Z
and R
2
)
(continued)
R
TG
1
): These components give gain
GX2
TGS
R
2
R
or 24.4 k .
´
and C
1
R
´
C
C´
2
TGS
are not used.
) resistive termi-
5-6396(F)
5-6397(F)
varied to give specified transmit gain.
R
ground via a resistor.
R
R
(for complex and resistive terminations) R
tions, the ratio of these resistors set the receive gain.
For resistive terminations, the ratio of these resistors
set the return loss characteristic. For complex termina-
tions, the ratio of these resistors set the low-frequency
return loss characteristic.
C
nents provide high-frequency compensation to the
return loss characteristic. For resistive terminations,
these components are not used. R
Set Z
Z
Z
R
R
125 V/A.
R
At dc, C
R
where M is the scale factor.
M =
It can be shown:
R
and
C
TG
T/R
T1
TGP
TGP
TGP
TGS
X
N
HB
1
TGS
´ || R
/R
/R
/R
: Sets hybrid balance for all terminations.
= R
24.4 k
----------------------- -
(the specified termination resistance) in the
T2
N1
must be 24.4 k to set SLIC transconductance to
= 24.4 k
= M x R1´
= M x R2´
TG
=
RCV
: With other components set, the transmit gain
R
/R
2
TGP
TGS
— gain shaping:
´ + C´ form.
1
/R
C
------
N2
M
GP
: For complex terminations, these compo-
|| R
and C´ are open.
: For both complex and resistive termina-
TGS
+ C
L8576B Dual Ringing SLIC
TGS
which is a scaled version of
CVN
is connected to
X
and R
T2
are
21