L9310 Line Interface and Line Access Circuit
Full-Feature SLIC, Ringing Relay, and Test Access Device
Data Sheet
July 2001
Transmit and receive gains have been chosen to mini-
mize the number of external components required in
the SLIC-codec ac interface, regardless of the choice
of codec.
Description (continued)
The L9310 will support the PPM application. A low-volt-
age PPM is injected at the PPMIN pin. PPMIN is a
high-impedance input that controls the PPM differential
voltage on tip and ring. The PPM signal may be
present at this pin at all times; however, PPM will only
be transmitted to tip and ring during a PPM active
mode. Activating or deactivating the PPMIN input will
not change the state of the SLIC device. The SLIC may
change states while the PPMIN input is active.
The L9310 uses a voltage feed, current sense architec-
ture; thus, the transmit gain is a transconductance. The
L9310 transconductance is set via a single external
resistor, and this device is designed for optimal perfor-
mance with a transconductance set at 300 V/A.
The L9310 offers an option for a single-ended to differ-
ential receive gain of either 8 or 2. These options are
mask programmable at the factory and are selected by
choice of part number.
Design equations relating the magnitude of the PPM
signal output at tip and ring to the PPM input signal at
PPMIN and information on PPM cancellation are given
in the Special Functions, Periodic Pulse Metering sec-
tion of this data sheet.
A receive gain of 8 is more appropriate when choosing
a first-generation type codec where termination imped-
ance, hybrid balance, and overall gains are set by
external analog filters. The higher gain is typically
required for synthesization of complex termination
impedance.
No PPM shaping is done by the L9310 device. It is
assumed that a shaped PPM input is presented to
PPMIN.
Maximum allowed PPM and dc current limit are related
by the overall drive capabilities of the tip and ring drive
amplifiers. These amplifiers can support up to 70 mA
dc current limit with a maximum 2.5 Vrms meter pulse
signal at tip and ring. These amplifiers can support up
to 45 mA dc current limit with a maximum 5 Vrms meter
pulse signal at tip and ring.
A receive gain of 2 is more appropriate when choosing
a third-generation type codec. Third-generation codecs
will synthesize termination impedance, set hybrid bal-
ance, and set overall gains. To accomplish these func-
tions, third-generation codecs typically have both
analog and digital gain filters. For optimal signal-to-
noise performance, it is best to operate the codec at a
higher gain level. If the SLIC then provides a high gain,
the SLIC output may be saturated, causing clipping dis-
tortion of the signal at tip and ring. To avoid this situa-
tion with a higher-gain SLIC, external resistor dividers
are used. These external components are not neces-
sary with the lower gain offered by the L9310.
If on-hook transmission of PPM is required, sufficient
overhead to accommodate on-hook transmission must
be programmed by the user at the OVH input. Over-
head is not increased during a PPM active mode.
Overhead may be changed during PPM active and
PPM not active modes by a change to the voltage pro-
grammed at the OVH input. See the Overhead Voltage
section of the dc Characteristics section for more
detail.
The RCVP/RCVN SLIC inputs are floating inputs. If
there is not feedback from RCVP/RCVN to VITR,
RCVP/RCVN may be directly coupled to the codec out-
put. If there is feedback, RCVP/RCVN must be ac-cou-
pled to the codec output.
Filtering of the meter pulse signal in the transmit direc-
tion may be necessary to prevent overload at the
codec inputs. Note that PPMOUT is provided as a con-
venient point to perform rejection of the meter pulse.
Via a resistor from PPMOUT to node ITR, a portion of
the PPM signal that is injected to tip and ring is phase
inverted and fed back to the transmit path to provide a
hybrid cancellation of the meter pulse signal in the
transmit direction.
This device is packaged in a 44-pin PLCC surface-
mount package.
This method of hybrid cancellation is adequate for
2.5 Vrms meter pulse. However, for higher-voltage
meter pulse, such as 5 Vrms, additional filtering may be
necessary. This may be done by a filter network at the
TXN input.
8
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
