L9214A/G
Low-Cost Ringing SLIC
Preliminary Data Sheet
October 2001
A receive gain of 2 is more appropriate when choosing
a third-generation type codec. Third-generation codecs
will synthesize termination impedance and set hybrid
balance and overall gains. To accomplish these func-
tions, third-generation codecs typically have both ana-
log 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 distor-
tion of the signal at tip and ring. To avoid this situation,
with a higher gain SLIC, external resistor dividers are
used. These external components are not necessary
with the lower gain offered by the L9214. See the Appli-
cations section of this data sheet for more information.
Description (continued)
Longitudinal balance is consistent with European ETSI
and North American GR-909 requirements. Specifica-
tions are given in Table 10.
Data control is via a parallel unlatched control scheme.
The dc current limit is programmable in the active
modes by use of an external resistor connected
between DCOUT and IPROG. Design equations for this
feature are given in the dc Loop Current Limit section
within the Applications section of this data sheet.
Programming range is 15 mA to 45 mA with VCC =
5.0 V and 15 mA to 35 mA with VCC = 3.3 V. Program-
ming accuracy is ±10% over this current range.
The L9214 is internally referenced to 1.5 V. The SLIC
output VITR is referenced to AGND; therefore, it must
be ac-coupled to the codec input. However, the SLIC
inputs RCVP/RCVN are floating inputs. If there is not
feedback from RCVP/RCVN to VITR, RCVP/RCVN
may be directly coupled to the codec output. If there is
feedback from RCVP/RCVN to VITR, RCVP/RCVN
must be ac coupled to the codec output.
Circuitry is added to the L9214 to minimize the inrush
of current from the VCC supply and to the battery supply
during an on- to off-hook transition, thus saving in
power supply design cost. See the Applications section
of this data sheet for more information.
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.
The L9214 is thermally protected to guard against
faults. Upon reaching the thermal shutdown tempera-
ture, the device will enter an all-off mode. Upon cool-
ing, the device will re-enter the state it was in prior to
thermal shutdown. Hysteresis is built in to prevent
oscillation.
The L9214 uses a voltage feed-current sense architec-
ture; thus, the transmit gain is a transconductance. The
L9214 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 L9214 is packaged in the 28-pin SOG, 32-pin
PLCC and 48-pin MLCC surface-mount packages. The
L9214A is set for gain of eight applications, and the
L9214G is set for gain of two applications.
The L9214 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 product code.
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.
6
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
