Analog Devices

Analog Devices


Targets: Audio, Automotive, Consumer, Mobile & Wireless

Analog Devices' SigmaDSP is a low-cost platform for audio processing. These processors use a 28-bit DSP that can perform full double precision (56-bit) operations. The 28-bit data word length provides +24 dB of headroom for 24-bit data inputs, which avoids the need for reducing a signal's dynamic range in order to implement signal-boosting filters or other signal processing functions. Included in the core are hardware accelerators that optimize it for audio processing functions. The SigmaDSP family includes parts with on-board 100 dB SNR audio ADCs and DACs to support analog I/O and eliminate the need for external converters. SigmaDSP's signal processing library makes it suitable for automotive head units and sound system amplifiers, consumer, and portable audio devices.

The ADAU1761 include 100dB SNR stereo audio ADCs and DACs that support sample rates from 8 kHz to 96 kHz, and a digital volume control. The analog input stage supports a stereo line input, a stereo analog microphone interface, and a circuit to supply the microphone bias voltage; it supports the standard for high-performance low-noise, digital microphones. The analog output stage includes two differential and three single-ended outputs, allowing for the direct connection of stereo headphones, an earpiece, and other output transducers. AC-coupled or "capless" configurations support the headphone interface. The differential line outputs can interface to a broad portfolio of the company's Class D power amplifiers. The serial control bus supports the I²C or SPI protocols, while the serial audio bus is programmable for I²S, left/right justified, or TDM modes. A programmable PLL supports flexible clock generation for all standard rates and available master clocks from 8 MHz to 27 MHz. SigmaStudio supports development for the ADAU1761.

Analog Devices ADAU1761 Block Diagram

The ADAU1442, ADAU1445, and ADAU1446 SigmaDSP audio processors include up to eight stereo asynchronous sample rate converters, an S/PDIF transceiver and serial inputs/outputs that support I2S and TDM formats. Any of these inputs can be routed to the SigmaDSP core or any of the outputs for maximum system flexibility. The SigmaDSP core of the new audio processor family features synchronous parameter loading for ensuring filter stability, and 100 percent code efficiency when used in conjunction with the company's SigmaStudio graphical development environment, which includes audio processing blocks such as FIR and IIR filters, dynamics processors, mixers, low-level DSP functions, and third-party algorithms.

The ADAU1701, ADAU1702, and ADAU1401 combine a SigmaDSP audio processor with 100 dB SNR ADCs and DACs and full stand-alone functionality to provide a full audio processing system on a single chip. These ICs can self-boot from an external EEPROM and have a 4-channel auxiliary ADC and GPIO pins to enable hard ware control of the DSP.

The AD1940 and AD1941 are 75 MHz digital-only SigmaDSP processors with 16 digital I/O channels. The first generation SigmaDSP products, including the AD1953, have three high-performance (112 dB) audio DACs with the SigmaDSP core. Most of the SigmaDSPs are qualified over the -40 to 105° temperature range for operation in automotive applications.

Developers program the SigmaDSP devices with the SigmaStudio graphical development tool, which includes access to common audio signal processing elements such as IIR and FIR filters for EQ and cross-over, bass enhancement, multi-band dynamics processing, speaker placement and frequency compensation, and stereo image widening. This design can be linked directly to the SigmaDSP hardware and the SigmaStudio tool can be used as a real-time control surface for the design's parameters, allowing easy system tuning. Third-party algorithms, such as Dolby ProLogic II and SRS TruSurround XT are available for the SigmaDSP and integrate seamlessly into the SigmaStudio environment.