LUCL9311AP-D AGERE [Agere Systems], LUCL9311AP-D Datasheet - Page 42

• Manufacturer Part Number: LUCL9311AP-D
• Description: Line Interface and Line Access Circuit Full-Feature SLIC with High Longitudinal Balance, Ringing Relay,and GR-909 Test Access
• Manufacturer: AGERE [Agere Systems]

Ringing Relay, and GR-909 Test Access
ac Applications
ac Interface Network
Thus, it appears the solution is to have a SLIC with a
low gain, especially in the receive direction. This will
allow the codec to operate near its maximum output
signal (to optimize S/N), without an external resistor
divider (to minimize cost).
Note also that some third-generation codecs require
the designer to provide an inherent resistive termina-
tion via external networks. The codec will then provide
gain shaping, as a function of frequency, to meet the
return loss requirements. Further stability issues may
add external components or excessive ground plane
requirements to the design.
To meet the unique requirements of both types of
codecs, the L9311 offers two receive gain choices.
These receive gains are mask programmable at the
factory and are offered as two different code variations.
For interface with a first-generation codec, the L9311 is
offered with a receive gain of 8. For interface with a
third-generation codec, the L9311 is offered with a
receive gain of 2. In either case, the transconductance
in the transmit direction, or the transmit gain, is 300 .
This selection of receive gain gives the designer the
flexibility to maximize performance and minimize exter-
nal components, regardless of the type of codec cho-
sen.
Design Tools
The following examples illustrate the design tech-
niques/equations followed to design the ac interface
with a first- or third-generation codec for both a resis-
tive and complex design. To aid the line circuit design,
Agere has available Windows *-based spreadsheets to
do the individual component calculations. Further,
Agere has available PSPICE
tion and verification. Consult your Agere Account Rep-
resentative to obtain these design tools.
42
(continued)
(continued)
†
models for circuit simula-
First-Generation Codec ac Interface Network
Termination impedance may be specified as purely
resistive or complex, that is, some combination of
resistors and capacitors that causes the impedance to
vary with frequency. The design for a pure resistive ter-
mination, such as 600 , does not vary with frequency,
so it is somewhat more straightforward than a complex
termination design. For this reason, the case of a resis-
tive design and complex design will be shown sepa-
rately.
First-Generation Codec ac Interface Net-
work: Resistive Termination
The following reference circuit shows the complete
SLIC schematic for interface to the Agere T7504 first-
generation codec for a resistive termination imped-
ance. For this example, the ac interface was designed
for a 600
with transmit gain and receive gain set to 0 dBm.
Also, this example illustrates the device with a single
battery operation, fixed current limit, and fixed loop clo-
sure threshold. This is a lower feature application
example.
Resistor R
match of input bias voltage at the RCVN/RCVP inputs.
If it is not used, there may be a slight offset at tip and
ring due to mismatch of input bias voltage at the
RCVN/RCVP inputs. It is very common to simply tie
RCVN directly to ground in this particular mode of oper-
ation. If used, to calculate R
RCVN to ac ground should equal the impedance from
RCVP to ac ground.
* Windows is a registered trademark of Microsoft Corporation.
† PSPICE is a registered trademark of MicroSim Corporation.
GN
resistive termination and hybrid balance
is optional. It compensates for any mis-
GN
, the impedance from
Agere Systems Inc.
July 2001