AM79Q4457J ETC1 [List of Unclassifed Manufacturers], AM79Q4457J Datasheet - Page 10

• Manufacturer Part Number: AM79Q4457J
• Description: Quad Subscriber Line Audio Processing Circuit-Non-Programmable (QSLAC-NP) Devices
• Manufacturer: ETC1 [List of Unclassifed Manufacturers]

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.
10
Am79Q4457/5457 Data Sheet
Data transmitted or received on the PCM highway is an
8-bit, A-law or -law companded code. The QSLAC-NP
device is compatible with both codes. Code selection is
provided via a device pin (A/µ). 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 (FSR
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-
v ic e w i t h s e r i a l c o n t r o l o f g a i n a n d b a la n c e
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
Yes
No
No
Package
44 PLCC
32 PLCC
44 TQFP
44 TQFP
N
and FSX
Am79Q4457 JC
Am79Q5457 JC
Am79Q4457 VC
Am79Q5457 VC
Part Number
N
) at rates