SA3291 Datasheet, PDF (14/20 Pages) ON Semiconductor – Preconfigured Wireless DSP System for Hearing Aids

AYRE SA3291
There are 3 modes of operation:
• Digital VC
• Momentary Memory Select
• Mixed Mode
In Mixed Mode, the switches behaviour is configurable to
be set to that a short or long press of the switch will invoke
either a memory or VC change (i.e., a short press is
a memory select, a long press is a VC change).
There is a programmable threshold that can be used to set
the timing behaviour.
Volume Control
The VC can be either external (digital VC) or
programmable. When using a Digital Volume Control
(DVC) with the Ayre SA3291, the switch should be
connected to the VC and D_VC pins 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 7 shows how to wire the
DVC to SA3291.
A toggle switch can be used as a DVC, momentarily
connecting the VC to either Vreg or GND. By connecting the
VC to Vreg, the volume will be increased one step, and by
connecting the VC to GND, the volume will be decreased
one step.
The following parameters can be programmed into the
hybrid to specify the DVC functionality:
• DVC enable or disable
• Volume up/down step size of 1 dB, 2 dB, 3 dB or 4 dB
• Volume up/down beep frequency and volume
• DVC range between 0 dB and 48 dB in 1 dB steps
• Default DVC value when the hybrid is powered up
• Volume up/down beep enable
• Max/Min beep enable
• Max/Min beep frequency & volume
If the Max/Min beep is enabled then when the volume has
been incremented to the maximum value of the specified
DVC range the device will play two beeps to indicate that it
cannot increase the volume any more. The same is true for
decrementing the volume and reaching the minimum value
of the DVC range.
GND
VC
Memory Select Switches
One or two, two−pole Memory Select (MS) switches can
be used with the Ayre SA3291. This enables users
tremendous flexibility in switching between configurations.
These switches may be either momentary or static and are
configurable to be either pull−up or pull−down through the
settings tab in IDS.
Up to six program modes can be configured on the Ayre
SA3291. Memory A must always be valid. All memory
select options are selectable via the settings tab in IDS.
Momentary Switch on MS
This mode uses a single momentary switch on MS (Pin 17)
to change program modes. Using this mode causes the part
to start in memory A, and whenever the button is pressed, the
next valid memory is loaded. When the user is in the last
valid memory, a button press causes memory A to be loaded.
This mode is set by programming the ‘MSSMode’
parameter to ‘Momentary’ and ‘Donly’ to ‘disabled’.
Example:
If 6 valid program modes: ABCDEFABCDEF…
If 5 valid program modes: ABCDEABCDE…
If 4 valid program modes: ABCDABCDA…
If 3 valid program modes: ABCABCA…
If 2 valid program modes: ABABA…
If 1 valid program mode: AAA…
Momentary Switch on MS, Static Switch on MS2 (Jump
to Last Memory)
This mode uses a static switch on MS2 (Pin 16) and
a momentary switch on MS (Pin 17) to change program
modes. If the static switch is OPEN, the part starts in
memory A and behaves like momentary, with the exception
that memory D is not used. If the static switch on MS2 is set
to HIGH, the part automatically jumps to memory D (occurs
on start−up or during normal operation). In this setup, the
momentary switch’s state is ignored, preventing memory
select beeps from occurring. When MS2 is set to OPEN, the
part loads in the last select memory.
This mode is set by programming the ‘MSSMode’
parameter to ‘Momentary’ and ‘Donly’ to ‘enabled’.
Example:
If MS2 = OPEN and there are 6 valid program modes:
ABCEFABCEF…
If MS2 = OPEN and there are 5 valid program modes:
ABCEABCE…
If MS2 = OPEN and there are 4 valid program modes:
ABCABCA…
If MS2 = OPEN and there are 3 valid program modes:
ABABA…
If MS2 = HIGH: D…
D_VC
Figure 7. Wiring for Digital Volume Control
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