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CML ADM voice codec provides full duplex functions

Posted: 24 Dec 2004 ?? ?Print Version ?Bookmark and Share

Keywords:cmx649? adaptive delta modulation voice codec? adm voice codec?

The CMX649 adaptive delta modulation (ADM) voice codec from CML Microcircuits provides full duplex codec functions optimized for cost effective, portable, wireless applications.

Primarily intended for cordless headsets and hand-free systems, this new product offers robust, error tolerant coding and low power consumption (drawing an operational 1.9mA at 2.7V). A multi-mode audio codec IC for wireless digital voice/audio communication, this new product is also suitable for consumer and industrial applications, including PC speech-to-text applications, digital voice storage/playback, telematic voice recognition systems and digital radio (TDD).

According to the company, low power and versatility are just two of the distinguishing features of the CMX649. The device offers full-duplex ADM, continuously variable slope delta modulation (CVSD) and PCM (linear, A law,?(mu) law and linear) operating modes. CMX649 operating modes and algorithms are user-configurable, so as to select the best data rate and voice quality for each application.

Additionally, robust ADM coding (e.g. CVSD) reduces host protocol and software burdens by eliminating the need for forward-error-correction, framing protocols and algorithm processing. One particular CMX649 CVSD mode provides 64kbps coding to support Bluetooth compatible customer designs.

Independent Tx and Rx powersave modes also support low power operation in all modes, which the company claims are lower than that of competitors. The product's ability to 'tune' many on-chip sections to provide reduced power consumption allows product design engineers to develop optimal power-requirement strategies for specific applications, added CML.

The press release also said that integrated on-chip functions eliminate the need for external circuits, including DSP, audio-gain, sidetone, mic-gain, audio filtering and PLL data clock recovery. With its C-BUS serial interface, the CMX649 promises to reduce the cost, size and design effort required to interface analogue 'voice' signals to digital wireless transceivers.

Other features

Additional product features include a programmable voice activity detector (VAD) with adjustable threshold level and attack/decay times; a transcoder to convert between different voice coding schemes; and a selectable digital scrambler for coded signal privacy and efficiency in modulation.

According to the company, CVSD/ADM coding offers many advantages to wireless voice communications projects. Major among these are: 'Best-fit' and versatile solutions to most over-air requirements, good quality output audio, high tolerance to data errors and no need for complex error correction schemes.

The CMX649 is housed in 20-pin plastic SOIC and TSSOP packages. An evaluation kit is also available (DE6491 wireless voice link demonstration kit).




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