SA3229 Datasheet, PDF (7/16 Pages) ON Semiconductor – Preconfigured DSP System

RHYTHM SA3229
SA3229 OVERVIEW
SA3229 is a DSP system implemented on
ON Semiconductor’s Wolverine hardware platform.
Wolverine is the hearing industry’s first 90 nm
Silicon−on−Chip platform enabling design of
highly−efficient and flexible hearing aid solutions. The
device is packaged for easy integration into a wide range of
applications from CIC to BTE. SA3229 can be used as a
trimmer adjustable device. It may be configured as one, two
or four channels with linear or WDRC processing.
Configuration data stored in non−volatile memory defines
hearing−aid parameters. SA3229 can be programmed via
the SDA or I²C programming interfaces.
The DSP core implements Adaptive Feedback
Cancellation, compression, wideband gain, and volume
control. The Adaptive Feedback Canceller reduces acoustic
feedback while offering robust performance against pure
tones.
SA3229 is an economical variant of SB3229 which
utilizes the on−chip non−volatile memory on Wolverine
(OTP) to offer the extended Rhythm feature set in a low−cost
solution. Device settings are programmed into the OTP
memory during manufacturing and fitting adjustments can
be made with up to four trimmers.
SA3229 and SB3229 feature identical parameter sets.
Therefore, SB3229 can be used for design and development
purposes. At manufacturing time, customers have the option
to migrate to the cost−efficient SA3229 variant, enabling
low−cost Bill−of−Materials for cost sensitive applications.
SA3229 supports two times programming, which provides
flexibility to rework the product, should any design changes
be needed.
Development of SA3229 based products is identical to the
SB3229 products using identical ARK libraries. The
SA3229 hybrid, however, can only be programmed in a
manufacturing environment using Cal/Config.
During 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.
FUNCTIONAL BLOCK DESCRIPTION
A/D and D/A Converter
The system’s A/D converter is a 2nd−order sigma−delta
modulator operating at a 2.048 MHz sample rate.
The system’s input is pre−conditioned with anti−alias
filtering and a programmable gain pre−amplifier. The
analog output is oversampled and modulated to produce a
1−bit pulse density modulated (PDM) data stream. The
digital PDM data is then decimated down to pulse−code
modulated (PCM) digital words at the system’s sampling
rate of 32 kHz.
The D/A is comprised of a digital 3rd−order sigma−delta
modulator and an H−bridge. The modulator accepts PCM
audio data from the DSP path and converts it into a 64−times
oversampled, 1−bit PDM data stream, which is then
supplied to the H−bridge. The H−bridge is a specialized
CMOS output driver used to convert the 1−bit data stream
into a low−impedance, differential output voltage
waveform suitable for driving zero−biased hearing aid
receivers.
Analog Inputs
SA3229 provides for up to four analog inputs,
Microphone 1 (MIC1), Microphone 2 (MIC2), Telecoil
(TCOIL) and Direct Audio Input (DAI) with the following
configurable front end modes:
• MIC1
• MIC2
• DAI
• TCOIL
• MIC1 + TCOIL
• MIC1 + DAI
Attenuation can be applied to the MIC1 input when
mixing with either TCOIL or DAI inputs.
Analog input signals should be ground referenced to
MGND. (Microphones, telecoils, DAI). MGND is
internally connected to GND to minimize noise, and should
not be connected to any external ground point.
Channel Processing
Figure 4 represents the I/O characteristic of independent
AGC channel processing. The I/O curve can be divided into
four main regions:
• Low input level expansion (squelch) region
• Low input level linear region
• Compression region
• High input level linear region (return to linear)
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