MT93L04 Zarlink Semiconductor, MT93L04 Datasheet - Page 22

• Manufacturer Part Number: MT93L04
• Description: 128-channel Voice Echo Canceller
• Manufacturer: Zarlink Semiconductor

Description of the Single MT93L00
Device Overview
The MT93L00 architecture contains 32 echo cancellers divided into 16 groups. Each group has two echo
cancellers, Echo Canceller A and Echo Canceller B. Each group can be configured in Normal, Extended Delay or
Back-to-Back configurations. In Normal configuration, a group of echo cancellers provides two channels of 64 ms
echo cancellation, which run independently on different channels. In Extended Delay configuration, a group of echo
cancellers achieves 128 ms of echo cancellation by cascading the two echo cancellers (A & B). In Back-to-Back
configuration, the two echo cancellers from the same group are positioned to cancel echo coming from both
directions in a single channel, providing full-duplex 64 ms echo cancellation.
Each echo canceller contains the following main elements (see Figure 4).
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Each echo canceller in the MT93L00 has four functional states: Mute, Bypass, Disable Adaptation and Enable
Adaptation. These are explained in the section entitled Echo Canceller Functional States.
Adaptive Filter for estimating the echo channel
Subtractor for cancelling the echo
Double-Talk detector for disabling the filter adaptation during periods of double-talk
Path Change detector for fast reconvergence on major echo path changes
Instability Detector to combat oscillation in very low ERL environments
Non-Linear Processor for suppression of residual echo
Disable Tone Detectors for detecting valid disable tones at send and receive path inputs
Narrow-Band Detector for preventing Adaptive Filter divergence from narrow-band signals
Offset Null filters for removing the DC component in PCM channels
12 dB attenuator for signal attenuation
Parallel controller interface compatible with Motorola microcontrollers
PCM encoder/decoder compatible with µ/A-Law ITU-T G.711 or Sign-Magnitude coding
Zarlink Semiconductor Inc.
MT93L04
22
Data Sheet