AGC as advanced output limiter in TLV320AIC3254

Sorry, we settled for the AIC3204, not the 3254. The AGC function seems to be identical for the two, though. Eggz

Hi, Eggz,

Welcome to E2E and thank you for your interest in our products.

The AGC goal is try to reach the target level. When the input signal is greater than the target level, it will be attenuated. By other hand, when the input signal is lower than the target level, the AGC will try to amplify the signal with a specified gain. This gain can be limited by the maximum PGA gain parameter. All the signals under the noise threshold will not be amplified if this threshold is enabled.

It is suggested not to use the AGC in noisy environments because the noise is added to the input signal. This noise is affected by the AGC. So, it could be amplified or attenuated by the AGC. If the noise threshold is enabled, the noise will be muted. But once the noise threshold is exceeded, all the input will be affected by the AGC. So, it is recommended to minimize the noise source to have a cleaner input signal.

Regarding your application, if my understanding is correct, you try to change the target level linearly. It could be possible changing the target level in specified intervals.

For more information about the AGC function, please take a look of the following document: http://www.ti.com/lit/an/slaa446/slaa446.pdf

I hope this helps you. If you still have questions or comments, please let me know.

Best regards,

Luis Fernando Rodríguez S.

Hi Luis Fernando Rodríguez S,

Thanks for your indepth reply to my AGC request.
You confirm my understanding of the AGC function. And I have experienced what you suggest, that the AGC should not be used in noisy environments.
Actually, I would like a 'DRC' like functionality in recording mode: linear gain until a set max level, whereafter the gain is reduced.
I didn't quite follow you description "change the target level linearly", but if the AGC still would amplify soft sounds (above noise threshold) I'm afraid this will not work for me.

Thanks!

Eggz

 

A Message from the TI E2E™ Community   Luis Fernando Rodríguez S. replied to AGC as advanced output limiter in TLV320AIC3254. Hi, Eggz, Welcome to E2E and thank you for your interest in our products. The AGC goal is try to reach the target level. When the input signal is greater than the target level, it will be attenuated. By other hand, when the input signal is lower than the target level, the AGC will try to amplify the signal with a specified gain. This gain can be limited by the maximum PGA gain parameter. All the signals under the noise threshold will not be amplified if this threshold is enabled. It is suggested not to use the AGC in noisy environments because the noise is added to the input signal. This noise is affected by the AGC. So, it could be amplified or attenuated by the AGC. If the noise threshold is enabled, the noise will be muted. But once the noise threshold is exceeded, all the input will be affected by the AGC. So, it is recommended to minimize the noise source to have a cleaner input signal. Regarding your application, if my understanding is correct, you try to change the target level linearly. It could be possible changing the target level in specified intervals. For more information about the AGC function, please take a look of the following document: http://www.ti.com/lit/an/slaa446/slaa446.pdf I hope this helps you. If you still have questions or comments, please let me know. Best regards, Luis Fernando Rodríguez S.     You received this notification because you subscribed to the forum.  To unsubscribe from only this thread, go here. Flag this post as spam/abuse.

Hi, Eggz,

Once the noise threshold is exceeded, the AGC will try to reach the target level. You may try disabling the noise threshold to see the effects of the AGC on the noise. Additionally, you may try configuring the maximum PGA gain from the lowest value to the highest value. This is to be sure if your application is not suitable for noisy environments.

Best regards,
Luis Fernando Rodríguez S.

Hi Luis Fernando,
Yes, we tried with max PGA values and it gets  indeed too noisy, unfortunately.
I'll be turning the agc off.
Would you be able to recommend another TI data converter chipset with a more flexible agc / limiter functionality?
Again,  thanks for your support.

Eggz

Hi, Eggz,

First, I suggest to use some anti-noise techniques to reduce the undesired signals on the input. You may use a differential microphone or a digital microphone to reduce the noise at the input. It would be fine to have a better control on the AGC.

Then, the AGC block is similar in all the codecs. If you require more algorithms to control the gain, I would suggest to use the TLV320AIC3254. It is similar to the TLV320AIC3204, but it has a programmable miniDSP. The miniDSP has predefined algorithms such filters, gains, mixers, etc. They can be programmed to process the signal in the codec.

I hope this helps you. If you still have questions, please let me know.

Best regards,

Luis Fernando Rodríguez S.

Hi Luis Fernando,

Great - the TLV320AIC3254 looks like an interesting alternative.

Can it simply replace the AIC3204 from a PCB/hardware perspective? I do understand that the miniDSP will require software changes.

Best regards,

Eggz

 

A Message from the TI E2E™ Community   Luis Fernando Rodríguez S. replied to AGC as advanced output limiter in TLV320AIC3254. Hi, Eggz, First, I suggest to use some anti-noise techniques to reduce the undesired signals on the input. You may use a differential microphone or a digital microphone to reduce the noise at the input. It would be fine to have a better control on the AGC. Then, the AGC block is similar in all the codecs. If you require more algorithms to control the gain, I would suggest to use the TLV320AIC3254. It is similar to the TLV320AIC3204, but it has a programmable miniDSP. The miniDSP has predefined algorithms such filters, gains, mixers, etc. They can be programmed to process the signal in the codec. I hope this helps you. If you still have questions, please let me know. Best regards, Luis Fernando Rodríguez S.     You received this notification because you subscribed to the forum.  To unsubscribe from only this thread, go here. Flag this post as spam/abuse.

Hi, Eggz,

You're right. The TLV320AIC3204 can be replaced by the TLV320AIC3254. They have the same pin structure. In order to use the miniDSP, it will be required to do software changes.

Best regards,
Luis Fernando Rodríguez S.