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L9214A

Low-Cost Ringing SLIC

Agere -> LSI Corporation 

L9214A/G

Low-Cost Ringing SLIC

Preliminary Data Sheet

October 2001

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.

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 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 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.

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.

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.

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 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.

6

Agere Systems Inc.

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