ZL38003 Data Sheet
4
Zarlink Semiconductor Inc.
2.1 In addition to the echo cancellers, the following functions are supported:
• 12 dB of noise reduction
• User gain control provided for speaker path (-24 dB to +21 dB in 3 dB steps)
• Gain pads at the Sin and Sout ports plus one at the input of adaptive filter (XRAM)
• Control of adaptive filter convergence speed during periods of double-talk, far end single-talk and near-end
echo path changes
• Control of Non-Linear Processor thresholds for suppression of residual non-linear echo
• Howling detector to identify when instability is starting to occur and to take action to prevent oscillation
• Narrow-Band Detector for preventing adaptive filter divergence caused by narrow-band signals
• Programmable high pass filters at Rin and Sin for removal of DC components in PCM channels
• Limiters that introduce controlled saturation levels
• Serial controller interface compatible with Motorola, National and Intel micro controllers
• PCM encoder/decoder compatible with m/A-Law ITU-T G.711, m/A-Law Sign-Mag or linear 2’s complement
coding
• Automatic gain control on the receive speaker path
• Idle channel noise suppression
3.0 Dual Codec Description
The CODEC Dual Codec provides complete audio to PCM interfaces including filtering and optional data
companding as required by the ITU-T G.711 & G.712 recommendations. Programmable gain allows adjustment for
a wide range of transducer sensitivities - two microphone amplifiers and four ear piece amplifiers are provided to
allow connection to a handset, headset, auxiliary channel and microphone/speaker. A cross-point circuit allows
either codec to be connected to any of the four audio interfaces. Programmable voltage sources are available for
electret biasing on the Microphone channels.
PCM voice data is passed via a serial interface which operates in ST-BUS or GCI mode. ST-BUS mode allows
the Codecs to be allocated to any of the 32 available channels. Control and programming of the Codecs is carried
out over a flexible serial micro-controller interface.
