TLV320ADC6140: TLV320ADC6140 Microphone Interface Circuit

Ben Cook

Part Number: TLV320ADC6140

Tool/software:

Dear friends,

I would like to interface four electret microphones to a TLV320ADC6140 ADC chip. My question is, what is the best way to go about this for optimal performance?

Should I use a pre-amp circuit, or can I connect directly to the ADC via AC coupling capacitors?

Additional context:

[1] All four microphones will be mounted to the same PCB as the ADC

[2] low noise / high SNR is a key factor... Achieving low phase distortion is even more important.

[3] I would also like to minimise size and cost, so component count is a consideration

[4] Required bandwidth - 50 Hz to circa. 16 kHz.

In summary:-

Do I require a preamp circuit like this:- (?)

Hopefully that is clear - happy to elaborate on any areas if you think I need to.

Thanks!

5 months ago

0 Jeff McPherson 5 months ago

TI__Mastermind 46995 points

Hi Ben,

Just wanted to let you know our engineer in India is owning this ticket and will follow up with you shortly.

Thanks for your patience,

Jeff McPherson

0 Lakshmi Narasimhan Badrinarayanan 5 months ago in reply to Jeff McPherson

TI__Expert 7830 points

Hi Ben,

Can you share the sensitivity and SNR spec of the microphone being used?

Thanks and Regards,

Lakshmi Narasimhan

0 Ben Cook 5 months ago in reply to Lakshmi Narasimhan Badrinarayanan

Prodigy 10 points

Yes of course.

The microphone part is AOM-5024P-HD-MB-R.

The datasheet is here: https://docs.google.com/gview?url=https://api.puiaudio.com/filename/AOM-5024P-HD-MB-R.pdf&embedded=true

The published sensitivity is -24 dB, and the SNR is 80 dB.

I am not too worried about adding gain, as I can use the PGA inside the ADC.

My question is whether I need a low impedance buffer in front of the ADC. The example you show in the datasheet seems to be specific to MEMs microphones, which have an internal buffer with a low impedance output.

Can I connect a biased ECM capsule directly to the ADC without distorting the signal?

Thanks,

Ben

0 Lakshmi Narasimhan Badrinarayanan 4 months ago in reply to Ben Cook

TI__Expert 7830 points

Hi Ben,

The datasheet of the microphone mentions an output impedance of 2.2kOhm.

The ADC6140 device supports three impedance modes: 2.5kOhm, 10kOhm and 20kOhm.

The 2.5kOhm may not be a suitable impedance option since it is very close to the microphone's impedance (If using this mode then pre-amp may be required).

At 20kOhm, the effect on the 2.2kOhm microphone impedance may be lesser, however there can be impact on Noise/Dynamic Range, as mentioned in the datasheet.

Thanks and Regards,

Lakshmi Narasimhan

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TLV320ADC6140: TLV320ADC6140 Microphone Interface Circuit