SA3291 datasheet(16/20 Pages) ONSEMI

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AYRE SA3291

www.onsemi.com

Power On Reset Delay

The programmable POR delay controls the amount of

time between power being connected to the hybrid and the

audio output being enabled. This gives the user time to

properly insert the hearing aid before the audio starts,

avoiding the temporary feedback that can occur while the

device is being inserted. During the delay period,

momentary button presses are ignored.

NOTE:

The values set in IDS are relative values from 0

to 11 seconds; not absolute. The POR delay is

relative to the configuration loaded on the

WOLVERINE platform.

Power Management Functionality

As the voltage on the hearing aid battery decreases, an

audible warning is given to the user indicating the battery

life is low. In addition to this audible warning, the hearing

aid takes other steps to ensure proper operation given the

weak supply. The exact hearing aid behaviour in low supply

conditions depends on the selected POR mode. The hearing

aid has three POR modes:

• Shallow Reset Mode

• Deep Reset Mode

• Advanced Mode

Shallow Reset Mode

In Shallow Reset mode, the hearing aid will operate

normally when the battery is above 0.95 V. Once the supply

voltage drops below 0.95 V the audio will be muted and

remain in that state until the supply voltage rises above

1.1 V. Once the supply voltage drops below the control logic

ramp down voltage, the device will undergo a hardware

reset. At this point, the device will remain off until the supply

voltage returns to 1.1 V. When the supply voltage is below

the control logic voltage, but above 0.6 V and rises above the

1.1 V turn on threshold, the device will activate its output

and operate from the memory that was active prior to reset.

If the supply voltage drops below 0.6 V, and rises above the

1.1 V turn on threshold, the device will reinitialize, activate

its output and operate from memory A.

Deep Reset Mode

In Deep Reset mode, the hearing aid will operate normally

when the battery is above 0.95 V. Once the supply voltage

drops below 0.95 V the audio will be muted. The device

remains in this state until the supply voltage drops below the

hardware reset voltage of 0.6 V. When this occurs, the

device will load memory A and operate normally after the

supply voltage goes above 1.1 V.

Advanced Reset Mode

Advanced Reset Mode on Ayre SA3291 is a more

sophisticated power management scheme than shallow and

deep reset modes. This mode attempts to maximize the

device’s usable battery life by reducing the gain to stabilize

the supply based on the instantaneous and average supply

voltage levels. Instantaneous supply fluctuations below

0.95 V can trigger up to two 3 dB, instantaneous gain

reductions. Average supply drops below 0.95 V can trigger

up to eighteen, 1 dB average gain reductions.

While operating with no instantaneous gain reductions, an

instantaneous supply voltage fluctuation below 0.95 V will

trigger an immediate 3 dB gain reduction. A waiting period

of 30 seconds is in place after the first instantaneous gain

reduction. Only after the waiting period has elapsed will an

instantaneous supply voltage fluctuation trigger the second

3 dB gain reduction. While an instantaneous gain reduction

is being applied, the instantaneous supply voltage level will

be checked every 30 seconds and a 3 dB gain reduction

removed should the level be above a certain threshold.

Should the average supply voltage drop below 0.95 V, the

device will begin to reduce the gain by 1 dB every 10

seconds until either the average supply voltage rises above

0.95 V or all 18 average gain reductions have been applied,

at which point the audio path will be muted. If the average

supply voltage returns to a level above 1.1 V, the audio path

will first be un−muted, if required. The gain will then be

increased by 1 dB every 10 seconds until either the average

supply voltage drops below 1.1 V, or all average gain

reductions have been removed. No action is taken while the

average supply voltage resides between 0.95 V and 1.1 V.

NOTE:

Instantaneous and average gain reductions are

adjusted independently.

When the instantaneous voltage falls below the hardware

shutdown voltage, the device will undergo a hardware reset.

When it turns back on because the voltage has risen above

the turn−on threshold, it will behave the same as it would in

shallow reset mode.

Low Battery Notification

Notification of the low battery condition via an acoustic

indicator is optionally performed when the battery voltage

drops below a configurable low battery notification

threshold. The low battery indicator is repeated every five

minutes until the device shuts down.

Software and Security

The Ayre SA3291 incorporates the following security

features to protect the device from cloning and against

software piracy:

• DLL protection by password − prevents a third party

from using IDS to reconfigure parts.

• Hybrid authentication by 128−bit fingerprint to identify

parts in application software − prevents a third party

from cloning a device’s EEPROM because the

fingerprint cannot be overwritten. Special functions can

be used in fitting software to reject parts that do not

match the expected fingerprint. This would prevent the

piracy of fitting software.

• DLL to hybrid pairing by using a software key in ARK

to match product libraries with client software − a part

can be ‘locked’ at manufacturing time so that it only

communicates with the library it was programmed with.

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