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AS3421 AS3422

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

is important to do a register dump of all OTP registers. This register backup in your system

memory is a backup of all register setting and is necessary

for the verification after the trim process to make sure that all bits are trimmed correctly. Once the register dump has been done it is important to

check the OTP_LOCK in register 0x35. This register indicates if the device is already trimmed or not. In case this bit is set to ‘1’ there is no more

trimming possible. The device has obviously already been trimmed before. In case the bit is ‘0’ there is initial or further trimming of the device

possible. You enter the trim mode and start the trimming process. Once the trimming is done the most important step is comparing the values

trimmed to the device with the original register dump we did right before we started with the actual trimming process. If the verification was

successful we know that all bits have been trimmed correctly to AS3501/AS3502. What is important to mention is that the AS3502 and AS3501

have a couple of test bits inside which are per default set to ‘1’. We do not recommend overwriting these bytes.

Furthermore it is important to know that it is not possible to change bits once they are trimmed. With AS3501 and AS3502 it is possible to trim the

device again if the MAIN_LOCK bit is not set to ‘1’. What is not possible is, is changing a bit from ‘1’ back to zero. If an additional trimming is

done it is only possible to change bits from ‘0’ to ‘1’. An example would be the following. A register contains a value of 0x41. If the MAIN_LOCK

from 0x41 to 0x43. It is important that all necessary bits are trimmed exactly like in the block diagram shown in

needs the MAIN_LOCK bit as well as the ALTx_LOCK bits to determine the right microphone register at start-up of the device. If the

MAIN_LOCK bit and the ALTx_LOCK bits are not set correctly the result can be malfunction of the device.

for detailed implementation of the I2C trimming there is also an application note available which describes the whole process in more detail and

includes also some code examples.