L9215A/G
Short-Loop Sine Wave Ringing SLIC
Data Sheet
September 2001
The L9215 uses a voltage feed-current sense architec-
ture; thus, the transmit gain is a transconductance. The
L9215 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 L9215 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 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.
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 L9215. See the Appli-
cations section of this data sheet for more information.
The L9215 is internally referenced to 1.5 V. This refer-
ence voltage is output at the V
REF
output of the device.
The SLIC output VITR is also referenced to 1.5 V;
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.
The L9215 is packaged in a 32-pin PLCC surface-
mount package and a 48-pin MLCC ultrasmall surface-
mount package. Use L9215A for gain of 8 applications
and L9215G for gain of 2 applications.
Description
(continued)
A common-mode current detector for tip or ring ground
detection is included for ground key applications. The
threshold is user programmable via external resistors.
See the Applications section of this data sheet for more
information on supervision functions.
Upon reaching the thermal shutdown temperature, the
device will enter an all off mode. Upon cooling, the
device will re-enter the state it was in prior to thermal
shutdown. Hysteresis is built in to prevent oscillation.
Longitudinal balance is consistent with European ETSI
and North American GR-909 requirements. Specifica-
tions are given in Table 6.
Data control is via a parallel unlatched control scheme.
The dc current limit is programmable in the active
modes via an applied voltage source. The voltage
source may be an external independent voltage
source. Also, the programming voltage may be derived
via a resistor divider network from the V
REF
SLIC out-
put. A programmable external voltage source may be
used to provide software control of the loop closure
threshold. Design equations for this feature are given in
the dc Loop Current Limit section of the Applications
section of this data sheet.
Programming range is 10 mA to 70 mA with V
CC
=
5 V and 10 mA to 45 mA with V
CC
= 3.3 V. Program-
ming accuracy is ±8% at 22 mA to 28 mA current limit.
Circuitry is added to the L9215 to minimize the inrush
of current from the V
CC
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.
Overhead is programmable in the active modes via an
applied voltage source. The voltage source may be an
external independent voltage source. Also the pro-
gramming voltage may be derived via a resistor divider
network from the V
REF
SLIC output.
If the overhead is not programmed, a default overhead
of approximately 6.0 V is achieved. This is adequate
for a 3.14 dBm overload into 900
Ω.
For the default
overhead, pin OVH is connected to ground. See the
Applications section of this data sheet for more infor-
mation.
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.
6
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
