SA3286 datasheet(13/16 Pages) ONSEMI

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INSPIRIA SA3286

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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 (Vb) 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 Vb 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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