LUCL8567AAU-D AGERE [Agere Systems], LUCL8567AAU-D Datasheet - Page 38

• Manufacturer Part Number: LUCL8567AAU-D
• Description: SLIC for Peoples Republic of China Applications
• Manufacturer: AGERE [Agere Systems]

L8567 SLIC for
People’s Republic of China Applications
dc Applications
Latched Parallel Data Interface
Table 24. Valid Data at NSTAT and NTSD
A simplified logic output latches schematic is shown in
Figure 30.
Like NSTAT, output NLED also reflects loop closure and
ring trip status. Output NLED is not latched. This output
is an open-collector output with sufficient drive capabil-
ity to drive an LED. Multiple NLED can be connected to
a common LED. NLED is valid regardless of the state
of EN. NLED can be used as an unlatched alternative
to NSTAT for control logic.
ac Design
There are four key ac design parameters. Termination
impedance is the impedance looking into the 2-wire
port of the line card. It is set to match the impedance of
the telephone loop in order to minimize echo return to
the telephone set. Transmit gain is measured from the
2-wire port to the PCM highway, while receive gain is
done from the PCM highway to the transmit port.
38
38
EN
EN
INTERNAL
LOOP
CLOSURE
DETECTORS
0
0
1
0
0
1
NRDET
NLC
Normal operation—device state deter-
Off-hook—loop closure or ring trip
mined by B0, B1, and RD1 inputs
Figure 30. Logic Output Latches
Device in thermal shutdown
Don’t care
Don’t care
On-hook
(continued)
State
State
CONTROL
(continued)
NSTAT
NTSD
NSTAT
EN
12-3455(F)
0
1
1
0
1
1
Finally, the hybrid balance network cancels the
unwanted amount of the receive signal that appears at
the transmit port.
First-Generation Codecs
These perform the basic filtering, A/D (transmit), D/A
(receive), and µ-law/A-law companding. They all have
an op amp in front of the A/D converter for transmit
gain setting and hybrid balance (cancellation at the
summing node). Depending on the type, some have
differential analog input stages, differential analog out-
put stages, and µ-law/A-law selectability. This genera-
tion of codecs is lower cost compared to second- and
third-generation codecs, but needs the most compli-
cated interface between the SLIC and codec. These
codecs are most suitable for applications with fixed
gains, termination impedance, and hybrid balance.
Second-Generation Codecs
This class of devices includes a microprocessor inter-
face for software control of the gains and hybrid bal-
ance. The hybrid balance is included in the device. ac
programmability adds application flexibility and saves
several passive components and also adds several I/O
latches that are needed in the application. However,
there is no transmit op amp, since the transmit gain and
hybrid balance are set internally.
Third-Generation Codecs
This class of devices includes the gains, termination
impedance, and hybrid balance—all under micropro-
cessor control. Depending on the device, it may or may
not include latches. This generation of codec offers a
very simple SLIC-codec interface with a minimal num-
ber of external components.
T7507 Codec
The T7507 provides third-generation codec functional-
ity without the programmability. In the T7507, ac gain,
termination impedance, and the hybrid balance net-
work are set digitally; thus, the SLIC-codec interface
requires virtually no external components.
However, because all the ac parameters are fixed (and
set for requirements in the PRC), the device is an
extremely cost-effective solution.
Lucent Technologies Inc.
August 1999
Data Sheet