SA3229 Datasheet, PDF (9/16 Pages) ON Semiconductor – Preconfigured DSP System

RHYTHM SA3229
taper, which is selectable via software. It is possible to use
a VC with up to 1 MW of resistance, but this could result in
a slight decrease in the resolution of the taper.
Trimmers
The trimmer interface provides the ability to control up to
19 hearing aid parameters through up to four trimmers.
A single trimmer parameter can have up to 16 values and
a single trimmer can control multiple parameters
(e.g., Trimmer 1 can control compression ratio in all four
channels simultaneously). The trimmer must be
three−terminal 100 kW to 360 kW variable resistors and have
a linear taper.
Parameters that can be assigned to trimmers include Low
Cut, High Cut, Compression Ratio, Wideband Gain,
Tinnitus (Noise Level, Low Cut Filter, High Cut Filter)
Crossover Frequency, Lower Threshold, Upper Threshold,
EQ Gain, Squelch Threshold, High Level Gain, Low Level
Gain, AGC−O Threshold, Static Volume Control and Peak
Clipper Threshold.
Digital Volume Control
The digital volume control makes use of two pins for
volume control adjustment, VC and D_VC, with
momentary switches connected to each. Closure of the
switch to the VC pin indicates a gain increase while closure
to the D_VC pin indicates a gain decrease. Figure 6 shows
how to wire the digital volume control to SA3229.
GND
VC
D_VC
Figure 6. Wiring for Digital Volume Control
Memory Select Switches
One or two, two−pole Memory Select (MS) switches can
be used with SA3229. This enables user s tremendous
flexibility in switching between configurations. Up to four
memories can be configured and selected by the MS
switches on SA3229. Memory A must always be valid. The
MS switches are either momentary or static and are fully
configurable through IDS in the IDS setting tab.
The behavior of the MS switches is controlled by two main
parameters in IDS:
MSSmode: this mode determines whether
a connected switch is momentary or static.
Donly: this parameter determines whether the MS2
switch is dedicated to the last memory position.
There are four basic MS switch modes of operation as shown
in Table 4 below.
Table 4. MS SWITCH MODES
MS Switch Mode
Mode 1
Mode 2
Mode 3
Mode 4
MS1 Switch
Momentary
Momentary
Static
Static
MS2 Switch
None
Static
Static
Static
Max # of Valid
Memories
4
4
4
3
Donly
Off
On
Off
On
MSSMode
Momentary
Momentary
Static
Static
Use
Simplest configuration
Jump to last memory
Binary selection of memory
Jump to last memory
The flexibility of the MS switches is further increased by
allowing the MS switches to be wired to GND or VBAT,
corresponding to an active low or active high logic level on
the MS pins. This option is configured with the
MSPullUpDown/MS2PullUpDown setting in the IDS
settings tab as shown in Table 5 below.
Table 5. MS SWITCH LOGIC LEVELS VS. IDS PULLUPDOWN SETTINGS
“PullUpDown” Setting in IDS
MS Switch State
MS Input Logic Level
Pulldown
CLOSED
HI
Pulldown
OPEN
LOW
Pullup
CLOSED
LOW
Pullup
OPEN
HI
Switch Connection
To VBAT
To VBAT
To GND
To GND
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