MT9125AE CMOS Dual ADPCM Transcoder

Description

The Dual-channel ADPCM transcoder is a low
power, CMOS device capable of two encoder
functions and two decoder functions. Two 64 kbit/s
PCM channels are compressed into two 32 kbit/s
ADPCM channels, and two 32 kbit/s ADPCM
channels are expanded into two 64 kbit/s PCM channels.
The 32 kbit/s ADPCM transcoding algorithm utilized
conforms to CCITT Recom-mendation G.721 and ANSI T1.303-1989.
The device also supports a 24 kbit/s (three bit word)
algorithm (CCITT/G.723).
Switching, on-the-fly, between 32 kbit/s and 24
kbit/s, is possible by toggling the appropriate Mode
Select (MS1-MS4) control pins.

Features

Dual channel full duplex transcoder
32 kbit/s and 24 kbit/s ADPCM coding,
compatible to G.721 & and G.723 (1988) and
ANSI T1.303-1989
Low power operation, total 25mW typical
Asynchronous 4.096 MHz master clock
operation
Transparent ADPCM bypass capability
Serial interface for both PCM and ADPCM data
streams
ST-BUS interface supported
Pin selected µ-law or A-law operation
Pin selected CCITT or sign-magnitude PCM
coding
Single 5 volt power supply
Optional reset value (CCITT Table 3/G.721)
capability

Applications

Pair gain
Voice mail systems
Wireless set base stations

Functional Block Diagram

Pin Connections