INSPIRIA GA3285

www.onsemi.com

6

Figure 4. Typical Hearing Instrument Assembly Diagram

T−coil

VC

+

+

CS44

+

−

MS

switch

(N.O.)

Zero Biased

Receiver

Front

Mic

Rear

Mic

INSPIRIA GA3285 OVERVIEW

Inspiria GA3285 is a DSP system with adaptive

algorithms that run on the ADVANCED hardware platform.

This hardware platform is a combination of a DSP core and

a high fidelity audio CODEC. The thinSTAX packaging

provides easy integration into a wide range of applications

from CIC to BTE.

The audio functions implemented on the CODEC include

tone generation, peak clipping and cross fading between

audio paths. The DSP core implements FrontWave

directional processing, programmable filters, adaptive

algorithms, compression, wideband gain, and volume

control. The adaptive algorithms include Adaptive Noise

Reduction, Adaptive Feedback Cancellation and Automatic

Adaptive Directional Microphones.

The Adaptive Noise Reduction reduces audible noise in

a low distortion manner while preserving perceived speech

levels. The Adaptive Feedback Canceller reduces acoustic

feedback while offering robust performance against pure

tones. The Adaptive Directional Microphone (ADM)

algorithm automatically reduces the level of sound sources

that originate from behind or from the side of the

hearing−aid wearer without affecting sounds from the front.

Additionally, the Automatic Adaptive Directional

Microphones algorithm automatically reduces current by

turning off the second input channel if it is not needed.

The iLog datalogging feature can be enabled to record

various parameters every 15 minutes during use of the

device. Once these parameter values are read from the

device, they can be used to counsel the user and fine tune the

fitting.

The Inspiria GA3285 is equipped with a noise source that

can be used in treating tinnitus. The Tinnitus Treatment

noise can be shaped and attenuated and then summed into

the audio path either before or after the volume control.

The Narrow−band Noise Stimulus feature allows the user

to generate stimuli from the device that can be used for in situ

audiometry.

The Inspiria GA3285 utilizes the power and capabilities

of the advanced platform to deliver advanced features and

enhanced performance previously unavailable to a product

in its class. As well, the Inspiria GA3285 contains security

features to protect clients’ Intellectual Property against

device cloning and software piracy.

SIGNAL PATH

There are two main audio input signal paths. The first path

contains the front microphone and the second path contains

the rear microphone, telecoil or direct audio input as selected

by a programmable MUX. The front microphone input is

intended as the main microphone audio input for single

microphone applications.

In FrontWave, ADM or Automatic ADM operation,

a multi−microphone signal is used to produce a directional

hearing instrument response. The two audio inputs are

buffered, sampled and converted into digital form using dual

A/D converters. The digital outputs are converted into

a 32 kHz or 16 kHz, 20−bit digital audio signal. Further IIR

filter blocks process the front microphone and rear

microphone signals. One biquad filter is used to match the

rear microphone’s gain to that of the front microphone. After

that, other filtering is used to provide an adjustable group

delay to create the desired polar response pattern during the

calibration process. In ADM and Automatic ADM, the two

microphone inputs are combined in an adaptive way while

in FrontWave operation the combination is static.