The SSM2160 and SSM2161 allow digital control of volume of six and four audio channels, respectively, with a master level control and individual channel controls. Low distortion VCAs (Voltage Controlled Amplifiers) are used in the signal path. By using controlled rate-of-change drive to the VCAs, the "clicking" associated with switched resistive networks is eliminated in the Master control. Each channel is controlled by a dedicated 5-bit DAC providing 32 levels of gain. A master 7-bit DAC feeds every control port giving 128 levels of attenuation. Step sizes are nominally 1 dB and can be changed by external resistors. Channel balance is maintained over the entire master control range. Upon power-up, all outputs are automatically muted. A three- or four-wire serial data bus enables interfacing with most popular microcontrollers. Windows™ software and an evaluation board for controlling the SSM2160 are available.
The SSM2160 can be operated from single supplies of +10 V to +20 V or dual supplies from ±5 V to ±10 V. The SSM2161 can be operated from single supplies of +8.5 V to +20 V (for automotive applications) or dual supplies from ±4.25 V to ±10 V. An on-chip reference provides the correct analog common voltage for single supply applications. Both models come in P-DIP and SO packages.