AM79Q4457 Datasheet, PDF(10/44 Page) List of Unclassifed Manufacturers – Quad Subscriber Line Audio Processing Circuit-Non-Programmable (QSLAC-NP) Devices

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AM79Q4457 Datasheet, PDF (10/44 Pages) List of Unclassifed Manufacturers – Quad Subscriber Line Audio Processing Circuit-Non-Programmable (QSLAC-NP) Devices

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FUNCTIONAL DESCRIPTION

The QSLAC-NP device performs the Codec/Filter and

two-to-four-wire conversion function (requires external

balance impedance) required of the subscriber line in-

terface circuitry in telecommunications equipment.

These functions involve converting an audio signal into

digital PCM samples and converting digital PCM sam-

ples back into an audio signal. During conversion, dig-

ital filters are used to band limit the voice signals. All of

the digital filtering is performed in digital signal proces-

sors operating from an internal clock, which is derived

from MCLK. The fixed filters set the transmit and re-

ceive gain and frequency response.

The transmit and receive gain can be altered on a per-

channel basis and the per-channel balance impedance

can be selected between two external impedances by

the Am79Q4457 QSLAC-NP device. Control of these

functions is provided by an integrated serial shift regis-

ter and latch per channel. These additional functions

are available on the Am79Q4457 device only.

Data transmitted or received on the PCM highway is an

8-bit, A-law or Âµ-law companded code. The QSLAC-NP

device is compatible with both codes. Code selection is

provided via a device pin (A/Âµ). The 8-bit codes appear

1 byte per time slot. The PCM data is read and written to

the PCM highway in time slots determined by the indi-

vidual Frame Sync signals (FSRN and FSXN) at rates

from 256 kHz to 4.096 MHz. Both Long- and Short-

Frame Sync modes are available in the QSLAC-NP de-

vice.

Two configurations of the QSLAC-NP device are of-

fered as pictured previously. The Am79Q4457 de-

vice with serial control of gain and balance

impedance is available in the 44-pin PLCC package

and 44-pin TQFP package. The Am79Q5457 device

without serial control is available in a 32-pin PLCC

package and 44-pin TQFP package.

Serial Control

Yes

Package

44 PLCC

32 PLCC

44 TQFP

Part Number

Am79Q4457 JC

Am79Q5457 JC

Am79Q4457 VC

Am79Q5457 VC

Am79Q4457/5457 Data Sheet

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