Programmable differential attenuator finds use in audio preamplifiers

That Corp. recently announced the That5171 SPI (serial-peripheral-interface)-controlled digital attenuator. The fully differential device serves as part of a differential-audio-signal path. You can set gain in 1dB steps. The part is compatible with the 1570 current-feedback differential-audio preamplifier. The IC operates from ±5 to ±17V supplies. It supports input-signal levels as high as 22dBu (decibels unloaded). That guarantees the gain error at a maximum of ±0.5dB. To reduce “zipper noise,” the sound from digital stepping of gain, the 5171 has a zero-crossing detector that prevents the part from changing gain until the signal is within 5 percent of 0V. The product also features a differential servo amplifier that you can set up as an integrator to reduce dc offsets to less than 1.5mV.

You control the 5171 using an addressable SPI port and use the four general-purpose 3.3V digital outputs to control input pads, analog switches, mute circuits, and LEDs. The SPI bus supports read-back so that your host software can verify proper operation. Applications include microphone preamplifiers, digitally controlled instrumentation amplifiers, digitally controlled differential amplifiers, and digitally controlled audio instrumentation. The 5171 comes in a 7x7-mm QFN package and operates in the -40°C to +85°C range.

That Corp.
Caption
You can use the THAT5171 differential attenuator in high-performance microphone pre-amplifier signal paths.