TLV320AIC3262 and TLV320AIC3268 filtering

Russell Wetherley1

Other Parts Discussed in Thread: TLV320AIC3262, TLV320AIC3268

Hello,

I am trying to use either the TLV320AIC3262 and TLV320AIC3268 for audio recording. I want to be able to use analog mics to record both near voices, as well as distant voices and loud noises. Is it possible to use either of these devices for that purpose since it would involve having different filters for different channels? I looked on the data sheet for both designs and was not able to find any specific answer to this question. I see that different filters are available, but not if they can be used with the codec at the same time. Thank you very much.

Regards,

Russell

over 11 years ago

0 J- over 11 years ago

TI__Mastermind 46195 points

Hi Russel,

In the TLV320AIC3262 application reference guide (http://www.ti.com/lit/pdf/slau309), you'll find the coefficient location for each channel. See Table 2-18. ADC Biquad Filter Coefficients as an example.

Regards,

J-

0 Jamaal_Charles over 11 years ago in reply to J-

Genius 3245 points

Hello,

Is it possible to direct one mic to 4 inputs on the ‘3262? Would I need additional buffering or would the ‘3262 inputs be enough? I assume this would be a separate blocking cap to each channel – is this the best approach?

Thank you

0 J- over 11 years ago in reply to Jamaal_Charles

TI__Mastermind 46195 points

Hi Jamaal,

An electret condenser microphone capsule is typically a membrane connected between the gate and source of a JFET. The voltage gain of this FET is proportional to the load resistance.

The AC load resistance is the MICBIAS pull-up resistor in parallel with all the input resistances in parallel. The input resistances can be calculated as explained in this wiki: http://e2e.ti.com/support/data_converters/audio_converters/w/design_notes/2764.how-to-calculate-the-input-resistance-of-an-aic-device.aspx.

The result will be a bit of drop in microphone gain.

Yes, you want to have independent blocking caps for each input to keep DC offsets at a minimum.

Regards,

J-

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TLV320AIC3262 and TLV320AIC3268 filtering