A New Wireless-Enabled Audio Processor for Hearing Aids and Cochlear Implants

Let's take a look at ON Semiconductor's new DSP-based hybrid IC solution that brings wireless connectivity to hearing aids and cochlear implants.

ON Semiconductor's new Ezairo 7150 SL is based on the Ezairo 7100 digital signal processor (DSP), which, according to this ON Semiconductor video, is "the industry's most integrated, flexible, and power-efficient mixed-signal DSP solution." My engineering experience does not include the design of hearing aids or cochlear implants, so I was quite impressed with all the computing power and other associated features that can be included in such hearing-assistance devices.

Figure 1. Highlighted features of the Ezairo 7150 SL hybrid solution. Image taken from this ON-Semiconductor video.

High-Precision Quad-Core Architecture

The Ezairo 7150 SL hybrid solution uses, at the heart of its design, the Ezairo 7100 system-on-chip (SoC), which has a quad-core architecture that is designed for low power consumption and yet performs 375 million instructions per second (MIPS)...or maybe it doesn’t (see below).
Take note that ON Semiconductor uses the phrase "quad-core architecture" and not "quad-core processor." So don't assume that this IC has four actual processors; according to the datasheet, the four "cores" are:

• CFX DSP
• HEAR configurable accelerator
• ARM Cortex−M3 processor subsystem
• Programmable filter engine

Furthermore, to allow a hearing-aid design team to properly balance their own design for optimal computing performance vs. power consumption, the Ezairo 7150 SL provides a configurable system clock speed; the designer can choose between one of twelve clock speed settings, ranging from 1.28 MHz to 15.36 MHz. Uh wait...375 MIPS with clock speeds ranging from 1.28MHz to 15.36MHz?! This doesn't make sense because processors perform, at the very best, one instruction for every clock pulse—some processor instructions require multiple clock pulses for completion. Therefore, in order to achieve 375 MIPS, either a clock speed of at least 375 MHz is required or a PLL must be used to increase the clock frequency. And while the datasheet does mention the use of a PLL, its stated purpose is "support for communication synchronization with wireless transceiver." Given this information, it appears that the 375 MIPS specification is a typo.

Figure 2. Block diagram of the Ezairo 7100 DSP-based system. Image courtesy of the Ezairo 7100 product brief.

Some Key Features

Given all the key features that are embedded in this hybrid solution, I'm quite impressed with its small size of only 7.46 × 4.04 × 1.78 mm (see image below).

Figure 3. Package dimensions of the Ezairo 7150 SL. Image courtesy of datasheet (PDF).

The magic behind the wireless transfer of data to and from multiple transceivers lies in the ARM Cortex M3 processor subsystem, which is fully programmable, includes hardwired CODECs, and supports error correction using Reed-Solomon and Hamming code.

To help put a designer's mind at ease—regarding hackers and hacking—the Ezairo 7150 SL includes built-in data security that encrypts any sensitive, or otherwise secret-sauce, algorithms, prior to storing the program data in the onboard EEPROM.

In an effort to help design teams more quickly design, test, and sell their behind-the-ear (BTE) hearing-aid devices, ON Semiconductor offers their Ezairo 7150 SL Reference Design Kit (see image below) which includes, as noted in the datasheet, the 0W705001GEVK demonstration board.

Figure 4. ON Semiconductor's Ezairo 7150 SL reference design kit. Image taken from this ON-Semiconductor video.

While other development tools are also available—including some tools specifically designed for assisting software developers—some of ON Semi's evaluation and development kits are only available under a nondisclosure agreement (NDA). Although I have not personally used development kits that require an NDA, I suppose requiring one is reasonable given that they make available, as advertised, a "full suite of comprehensive tools."

Control over BLE (CoBLE)

The ability for users of hearing aids and cochlear implants to control so many of their hearing-aid device's parameters is made possible by the functionality offered by Control over BLE (CoBLE). The previously mentioned reference design includes a sample Android phone app that demonstrates the CoBLE functionality (see image below). Using CoBLE, hearing aid users can perform the following:

• adjust hearing aid volumes
• check battery status
• make program changes
• receive incoming phone calls and text messages
• use the "Find Me" function to locate misplaced hearing aids

Figure 5. ON Semiconductor's Ezairo 7150 SL reference design includes CoBLE functionality. Image taken from this ON-Semiconductor video.

Also included—and this is really cool—is a proprietary protocol that enables, via a remote dongle, streaming of music to the hearing aids from external music sources, such as TVs, tablets, and smartphones; the advertised connectivity range is up to 10 meters. Nice! See the image below for a depiction of how this works.

Figure 6. ON Semiconductor's Ezairo 7150 SL reference design allows for audio streaming by use of an external dongle. Image taken from this ON-Semiconductor video.

Have you had a chance to use this new DSP-based hybrid IC for hearing aids? If so, leave a comment and tell us about your experiences.