AS3412 datasheet(42/84 Pages) AMSCO

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[v1-00] 2016-Apr-06

AS3412 − Detailed Description

If you want to read out the OTP fuse content, the OTP load

function is necessary. In order to load the OTP fuse content to

the OTP registers, a special sequence is necessary, as shown in

Figure 55.

Figure 55:

OTP Load Access Flow Chart

OTP Load Access Flow Chart: This flow chart shows how to successfully load the OTP fuse content back to the

OTP register via the I²C or production trimming interface.

OTP Fuse Process

Many wireless applications, like Bluetooth single chips support

programmable solutions, as well as ROM versions. As such, it is

necessary for ROM versions to store microphone gain

compensation data and the general ANC configuration inside

the ANC chip. This is necessary because there is no other way

to configure the ANC chip during startup. In order to guarantee

successful trimming of AS3412 it is necessary to provide a

decent environment for the trimming process. Figure 56 shows

a principal block diagram for trimming the AS3412 properly in

production using the I²C interface. The most important block is

the external power supply. Usually it is possible to trim the

AS3412 with a single supply voltage of min. 1.8V in laboratory

environment, but as soon as it comes to mass production VNEG

supply buffering is highly recommended. As highlighted in the

block diagram, it is mandatory to get a voltage difference

between VPOS and VNEG of 3.4V (minimum) to guarantee proper

trimming of the device, therefore it is possible to buffer it

externally with a negative power supply. The VNEG voltage

applied to VNEG pin must be lower than the voltage generated

by the charge pump. This means if the typical VNEG output

voltage is -1.5V you can apply externally -1.7V. The charge pump

enters then automatically skip mode.

Set bit EVAL_REG_ON

in register 0x20

Set OTP_MODE

Dummy read from

Wait 15ms

Dummy read from

Wait 15ms

Dummy read from

Wait 15ms

Dummy read from

OTP registers are successfully loaded with

OTP fuses content

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