Preliminary Data Sheet

September 2001

High-Voltage Ringing SLIC for VoIP Applications

L9500A

Agere Systems Inc.

25

ac Applications

ac Parameters

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 tele-

phone 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. Transmit and receive gains may be specified in terms of an actual gain, or in

terms of a transmission level point (TLP), that is the actual ac transmission level in dBm. Finally, the hybrid bal-

ance network cancels the unwanted amount of the receive signal that appears at the CODEC input.

GND

PT

+1

PR

35x

L9500

–1

3.0 V

1.0 V

71 V