Electret Condenser Microphone Selection Guidance for SGTL5000

[Luax]

Hi!

We are trying to implement audio record capability via an electret condenser microphone to our own carrier board for an Apalis iMX6 Computer on Module. This module has a SGTL5000 audio codec IC with a MIC input. Since there are hundreds of electret microphones available on the market with different electrical characteristics (Impedance, Current Rating, Sensitivity, Operating Voltage) and we have only little experience in this field, we kindly ask you to suggest us suitable electret condenser microphones for the Apalis iMX6 Computer on Module / the SGTL5000 audio codes IC.

According to the Apalis iMX6 datasheet, the MIC_BIAS pin of the SGTL5000 is not available. As an alternative to the suggested schematin in the SGTL5000 datasheet, can we simple connect the electret condenser microphone between the MIC_IN pin and AGND like shown in the attached drawing?

Kind regards,
Lukas

[matthias.tx]

Hello Luax,

The electret mics are not like Dynamic microphones that you can connect GND and Signal to an input amplifier. They are like condenser microphones and they need a basis (phantom voltage).

So you need to provide power and decouple the signal from the DC offset via a capacitor. It might be beneficial for your noise figure to use a little LDO for the MIC power rather then the 3.3 volt from the switching regulators.

On the other aspects it depends what your application needs. Can you tell me more about the application.

you can read more about them here. Electret Condenser Microphones PTM - CUI Devices │ DigiKey

Best Regards,

Matthias