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AS3400 AS3410 AS3430 1v0

Data Sheet - D e t a i l e d D e s c r i p t i o n

Registers 0x8, 0x9, 0xA, 0xB, 0xC and 0x21 have only effect when the corresponding “REG_ON” bit is set, otherwise the chip operates with the

OTP Register settings which are loaded from the OTP fuses at every start-up.

All registers settings can be changed several times, but will loose the content on power off. When using the I2C mode, the chip configuration has

to be loaded from the microcontroller after every start-up. In stand alone mode the OTP fuses have to be programmed for a permanent change

of the chip configuration.

A single OTP cell can be programmed only once. Per default, the cell is “0”; a programmed cell will contain a “1”. While it is not possible to reset

a programmed bit from “1” to “0”, multiple OTP writes are possible, but only additional unprogrammed “0”-bits can be programmed to “1”.

Independent of the OTP programming, it is possible to overwrite the OTP register temporarily with an OTP write command at any time. This

setting will be cleared and overwritten with the hard programmed OTP settings at each power-up sequence or by a LOAD operation.

The OTP memory can be accessed in the following ways:

executed after each power-on-reset.

can be invoked multiple times and will remain set while the chip is supplied with power and while the OTP register is not modified with another

WRITE or LOAD operation.

memory after a LOAD command.

empty batteries for burning the fuses.

Attention: If you once burn the OTP_LOCK bit, no further programming, e.g. setting additional “0” to “1”, of the OTP can be done.

For production, the OTP_LOCK bit must be set to avoid an unwanted change of the OTP content during the livetime of the product.

8.7.2 OTP Fuse Burning

In most stand alone applications, the I2C pins are not accessible. Burning the fuses can be done by switching the line inputs into a special mode

to access the chip by I2C over the line input connections. This allows trimming of the microphone gain with no openings in the final housing and

so no influence to the acoustic of the headset.

This mode is called “Application Trimm” mode, or short “APT”. (Patent Pending)

During the application trimm mode LINR has to provide the clock, while LINL has to provide the data for the I2C communication.

Please note that the OTP register cannot be accessed directly but have to be enabled before a read or write access. This is independent whether

you access the OTP register via the normal I2C pins or in application trimm mode via LINL and LINR. Please refer to the detailed register

description to get more information on how the registers can be accessed.

To achieve a proper burning of the fuses, the negative supply has to be buffered by applying an external negative supply during burning. This

voltage can also be applied to the LINL terminal. An internal switch is connecting LINL and VNEG during the fuse burning. LINR has to provide

the clock for burning the fuses.

The below flow chart shows the principle steps of the OTP burning process. The application trimm mode can only be entered at a specific timing

during the start-up sequence.

The device offers the possibility to change microphone gain settings 3 times by using alternative registers. The selection which register set is

being used to set the microphone gain is done by the “lock” bits of the corresponding registers.

A more detailed description of the individual steps is available in an application note.