STMicroelectronics and Infra-Com Develop Wireless Digital Audio Reference Design

Audio signals using Infra-Com’s IrGate wireless infrared protocol are processed by an IrGT801ADR Modem and Interface IC, which receives data from the infrared sensors in the optical/analog front-end via an LVDS (Low Voltage Differential Signaling) interface and drives the ST’s full digital amplifier through an I2S (Inter-IC Sound) serial digital audio interface.

The Drum solution embeds ST’s STA326, a fully-digital IC amplifier that is able to deliver 2x60W of audio power into 8 ohm loudspeakers. It provides true hi-fi audio quality, with an uncompressed 24-bit 48kHz PCM (Pulse Code Modulation) wireless link, and almost zero latency for perfect lip-sync. Latency is just 150 microseconds compared to typically more than 7ms for competitive RF-based solutions. Amplifier efficiency is up to 92% - among the highest in the market - allowing a compact heatsink and power supply to be used in the overall application. The amplifier enjoys full built-in over-current and over-temperature protection capabilities, and the all-digital audio stream maintains full audio quality and 100dB signal to noise ratio (SNR) and dynamic range.

The Violin solution embeds ST’s STA333ML, a fully-digital micro-less IC amplifier that is able to deliver 2x20W without the need of external heatsink. The STA333ML retains the highest digital audio quality without adding software development efforts.

DIR enables optical communication without the need for line-of-sight between the transmitting and receiving nodes. Unlike a direct infrared signal - which emits light in a narrow beam - a diffused infrared device floods the room with the infrared emissions and utilizes natural reflections from the ceiling, walls, floor and other surfaces to maintain robust high bit rate communications, unaffected by obstructions or by moving people within the enclosure. The link effectively behaves similarly to a radio signal within its operating space, but with no possibility of being affected by, or generating, radio frequency interference (RFI); it is also insensitive to remote control signals, and cannot be ‘overheard’ in an adjacent room. Additionally DIR is a worldwide unregulated technology operating at 870nm.

The STA326 single-chip audio system integrates digital audio processing, digital amplifier control and a DDX® digital power output stage. It can be configured easily via digital control to operate in one of several different output modes, and offers a full range of processing and equalization options, including up to 4 programmable 28-bit biquads per channel, and bass and treble tone control. The device is one of a range of single-chip and single-package audio products in ST’s Sound Terminal family; other amplifiers in the family can be used with the Drum design to satisfy different audio power requirements, from 2x1W up to 2x80W.

“The Drum is the first of a set of complete and easy-to-use turnkey designs for manufacturers of remote audio products, combining high quality amplification with the user convenience of diffused infrared technology,” said Andrea Onetti, General Manager of the Audio Division within ST’s Home Entertainment and Display Group. “The Drum and similar designs will complement other interfaces such as Bluetooth 2.0 EDR (Enhanced Data Rate), WiFi and UWB (Ultra-WideBand) in the Sound Terminal family, and we look forward to introducing a single-package DIR and digital amplification solution in the future.”

The Drum and Violin reference designs are available now as the M2C_IrGT801ADR_STA326 and M2C_IrGT801ADR_STA333ML modules, respectively, for evaluation and product development.

Infra-Com Ltd. focuses on the development and commercialization of innovative, low-cost semiconductor chipsets for indoor, short-range wireless applications. The company has achieved a technological breakthrough by enabling non-line-of-sight and high bit rate optical communications using the Diffused Infrared (DIR) approach. For more information visit www.infra-com.com.