GA3227 Datasheet, PDF (7/13 Pages) ON Semiconductor – Pre-configured DSP System

CONSOLIDATOR GA3227
TYPICAL APPLICATIONS (Cont’d)
MS
−
T−coil
Mic
+
CS44
Zero Biased
Receiver
VC
TR1 TR2 TR3
TR4
Figure 5. Typical Assembly Diagram
CONSOLIDATOR GA3227 OVERVIEW
The Consolidator GA3227 hybrid comprises a
configurable two−channel compressor circuit with two
methods of operation – extended programmable mode and
trimmer mode. The device can be configured as a one or two
channel device with linear or WDRC processing.
Configuration data stored in non−volatile memory defines
hearing aid parameters. This data needs to be uploaded to the
hybrid before the circuit becomes functional. The
Consolidator GA3227 hybrid is programmed via the SDA
pin using industry−standard programming boxes.
Configuration data is generated by an ARK product
component library (DLL). The Consolidator GA3227 is
fully supported by ON Semiconductor’s software tools
available from the ARK website: http://ark.onsemi.com/
During normal trimmer mode operation, a low−speed A/D
circuit monitors the positions of up to four manual trimmers
and a VC potentiometer. Trimmer position changes are
immediately interpreted and translated into new circuit
parameter values, which are then used to update the signal
path.
ON Semiconductor’s Library Manager tool in
ARKonline enables pre−defining of trimmer assignments
for all common functions such as low−cut, high−cut, AGC
parameters, wideband gain, and maximum power output
(MPO).
SIGNAL PATH
There are two main audio input signal paths. The first path
contains the microphone and second path contains the
telecoil input, as selected by a programmable MUX. The
microphone input is intended as the main audio input for
single−microphone applications. The two audio inputs are
buffered, sampled and converted into digital form using an
A/D converter. The digital output is then converted into a
24 kHz 20−bit digital audio signal.
In Telecoil mode, gains are trimmed during the
Cal/Config process to compensate for microphone/telecoil
mismatches. The telecoil input can also be used as a second
microphone input. In this case, the telecoil compensation
should be disabled. This can be done via the ARKonline
wizard.
The wideband detector circuit output is routed to a
band−split filter that divides the signal into two frequency
bands. There is an option to configure the hybrid as a single
channel device that simply shuts down and bypasses the
band−split filter. The gain in each channel is a function of the
overall detected wide−band energy. The two frequency
bands are then summed back into a wide−band signal.
Further processing capabilities include a 1st to 3rd order
low cut filter before the band−split filter. After the two
channels are summed together, there is a 1st or 2nd order
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