Integrated audio front ends significantly accelerate design processes in audio-based systems. With the ADAU1860 family, Analog Devices introduces a high-performance version of this chip genre. One unique selling point is the availability of a high-performance digital signal processor on the chip.

Before analyzing the chip, terminology needs to be clarified. In particular, Analog Devices refers to the chip at hand as the ADAU1860 family. The ADAU1860 can only be ordered by customers in the People's Republic of China, while the ADAU1860-1 is an ROW-only component. From a functional point of view, however, they behave the same way.

Analog front end with additional intelligence

The ADAU1860 can best be understood by looking at its functional block diagram, which presents itself as shown.

The leftmost component is an analog audio ingestion element, which means that circuit designers do not need to bother with custom analog/digital systems. Furthermore, the right-hand side provides a DAC - it permits direct output of headphone-friendly signals, thereby reducing the bill of materials.

Analog Devices provide high-resolution converters. The datasheet claims a 24-bit resolution, enough to handle even the highest fidelity signals found in consumer audio applications. The digital-to-analog converter provides a similar quality; interestingly, the data sheet also provides specifications for direct connections to various commonly used loads.

Harness the power of Tensilica digital signal processing

Analog Devices advertises the ADAU1860 family as ideally suited to applications where noise cancellation is required. This is achieved by the DSP core, which can be seen in the middle of the block diagram in the figure. It uses a digital signal processor purchased from Tensilica; specifically, the HiFi 3z DSP core architecture is used.

AD optimized the internal architecture to accelerate instructions commonly needed in noise cancellation applications. In particular, the data sheet claims the following:

The FastDSP core has a reduced instruction set that optimizes

the codec for noise cancellation. The program and parameter

random access memories (RAMs) accept a custom audio

processing signal flow built using the Lark Studio graphical user

interface (GUI).

Given that the parametrization of filter algorithms can be daunting, Analog Devices provides a system called Lark Studio at the URL https://www.analog.com/en/products/adau1860.html. It implements a flowchart-based development system that permits filter parameterization without advanced coding—the download is accessible after signing an NDA.

Focusing on data flow

Finally, a look at the whole system example explains the data flows.

As can be seen at the bottom of the schematic, the audio interface interacts with the Bluetooth module using both a control SPI and a data I2S interface. Audio information can be harvested using a standard class commonly implemented in all kinds of DSP libraries.

Conclusion

The ADAU1860 chip family provides circuit designers with a high-performance analog audio frontend and a DSP for filtering. This is a great way to reduce system complexity, as DSP integration can be omitted. The price is fully justified.