SA3286 Datasheet, PDF (13/16 Pages) ON Semiconductor – Pre-configured DSP System

INSPIRIA SA3286
In this mode, it is possible to jump from any memory to
any other memory simply by changing the state of both
switches. If both switches are changed simultaneously, then
the transition is smooth. Otherwise, if one switch is changed
and then the other, the part transitions to an intermediate
memory before reaching the final memory.
When MS2 is set HIGH, the state of the switch on MS is
ignored. This prevents memory select beeps from occurring
if switching MS when MS2 is HIGH. The part starts in
whatever memory the switches are selecting. If a memory is
invalid, the part defaults to memory A.
AGC−O and Peak Clipper
The output compression−limiting block (AGC−O) is an
output limiting circuit whose compression ratio is fixed at
∝:1. The threshold level is programmable. The AGC−O
module has programmable attack and release time
constants.
The AGC−O on the Inspiria SA3286 has optional adaptive
release functionality. When this function is enabled, the
release time varies depending on the environment. In
general terms, the release time becomes faster in
environments where the average level is well below the
threshold and only brief intermittent transients exceed the
threshold.
Conversely, in environments where the average level is
close to the AGC−O threshold, the release time applied to
portions of the signal exceeding the threshold is longer. The
result is an effective low distortion output limiter that clamps
down very quickly on momentary transients but reacts more
smoothly in loud environments to minimize compression
pumping artifacts. The programmed release time is the
longest release time applied, while the fastest release time is
16 times faster. For example, if a release time of 128 ms is
selected, the fastest release time applied by the AGC−O
block is 8 ms.
The Inspiria SA3286 also includes the Peak Clipper block
for added flexibility.
Memory Switch Fader
To minimize potential loud transients when switching
between memories, the Inspiria SA3286 uses a memory
switch fader block. When the memory is changed, the audio
signal is faded out, followed by the memory select acoustic
indicators (if enabled), and after switching to the next
memory, the audio signal is faded back in. The memory
switch fader is also used when turning the Tone Generator
on or off, and during SDA programming.
Power−On/Power−Off Behaviour and Low Battery
Indicator
During power−on, the Inspiria SA3286 hybrid is held in
a reset state until the supply voltage (V_b) reaches a turn−ON
threshold. A small portion of the hybrid’s internal control
logic turns on and monitors the voltage to determine if the
supply is stable. Once the supply is stable, the entire hybrid
is activated and loads its configuration. Finally, the audio
output turns on by smoothly transitioning to the expected
output level.
During normal operation, when a low battery condition is
detected, the Inspiria SA3286 hybrid plays out a
configurable acoustic indicator to indicate that the battery is
low. This is repeated every five minutes until the device
reaches the turn−OFF threshold. The low battery threshold
is programmable in IDS between 1.0 V and 1.2 V in 10 mV
increments.
If V_b drops below the turn−OFF threshold, then the
Inspiria SA3286 hybrid is returned to its reset state and the
audio output is muted. After a reset due to a low battery or
a sudden supply transient, the recovery behaviour of the
Inspiria SA3286 is determined by the selectable reset mode
through ARKonline.
There are four selectable reset modes as follows:
• Shallow−reset mode − After a low battery shutdown or
transient shutdown, it allows the Inspiria SA3286
hybrid to immediately restart when the supply voltage
rises above the turn−ON threshold. The device restarts
in the memory that was last active when the shut down
occurred. In summary, the device functions until the
supply voltage drops below the turn−OFF threshold,
and recovers when the device rises above the turn−ON
threshold again.
• Deep−reset mode − After a low battery shutdown or
transient shutdown, it does not allow the Inspiria
SA3286 hybrid to restart. When a shutdown occurs
(i.e., the supply voltage drops below the turn−OFF
threshold), the device remains off until the supply
voltage drops below approximately 0.3 V and
subsequently rises above the turn−ON threshold. For
the supply to drop below 0.3 V, the battery should be
disconnected. Upon reconnecting the battery
(preferably a new battery) the supply voltage rises
above the turn−ON threshold, and depending if the
supply is stable, the device restarts.
• Mixed mode − A combination of the first two modes.
The device starts up in shallow−reset mode initially,
then transitions to deep reset mode after five minutes.
• Advanced reset mode (recommended) − A more
advanced combination of the first two modes, plus
some additional intelligence. The device starts up in
shallow−reset mode initially, so that after a low battery
shutdown or a transient shutdown, the device
immediately restarts when the supply voltage rises
above the turn−ON threshold. When the device restarts,
deep−reset mode is applied and the device operates in
the memory that was last active when the shut down
occurred. Additionally, the maximum output level is
reduced through a 2 dB reduction of the AGCo and
peak clipper. This operating condition is defined as
transient reboot mode. The device operates in transient
reboot mode (i.e., deep−reset mode and maximum
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