SSM2166*

The SSM2166* integrates a complete and flexible solution for conditioning microphone inputs in computer audio systems. It is also excellent for improving vocal clarity in communications and public address systems. A low noise voltage controlled amplifier (VCA) provides a gain that is dynamically adjusted by a control loop to maintain a set compression characteristic. The compression ratio is set by a single resistor and can be varied from 1:1 to over 15:1 relative to a user defined "rotation point;" signals above the rotation point are limited to prevent overload and eliminate "popping." In the 1:1 compression setting the SSM2166 can be programmed with a fixed gain of up to 20 dB; this gain is in addition to the variable gain in other compression settings. The input buffer can also be configured for frontend gains of 0 dB to 20 dB. A downward expander (noise gate) prevents amplification of noise or hum. This results in optimized signal levels prior to digitization, thereby eliminating the need for additional gain or attenuation in the digital domain that could add noise or impair accuracy of speech recognition algorithms. The compression ratio and time constants are set externally. A high degree of flexibility is provided by the VCA Gain, Rotation Point, and Noise Gate adjustment pins.

The SSM2166* is an ideal companion product for audio codecs used in computer systems, such as the AD1845 and AD1847. The device is available in 14-lead SOIC and P-DIP packages, and guaranteed for operation over the extended industrial temperature range of 40°C to +85°C. For similar features/performance in an 8-lead package, please refer to the SSM2165.