TLV320AIC3268: What is the use able frequency range?

Manjula Ellepola

Part Number: TLV320AIC3268

Hi Forum

We have an ultrasonic application where we would want to generate and receive tones up to 70kHz. The above device has a ref design for ultrasonic distance measurement. In the description of this ref design TI says that a 40kHz system was implemented using 96kHz sampling rate. Also the description says that higher frequencies are possible with 192kHz sampling.

However when I look through the data sheet I see that the decimation filter C has to be used for 192kHz and the pass band is limited to 21kHz (0.11fs) even though the sampling rate is that high. This means that higher frequencies such as 70kHz cannot be generated and received due to the limitations of this filter. Am I missing something here? Is it indeed possible to generate and receive frequencies say up to 80 kHz with this device?

The other question is why have a sampling frequency of 192kHz if it's use able range is only 21kHz?

Look forward to your expertise.

Best regards

Manjula

over 8 years ago

0 Luis Fernando Rodriguez S. over 8 years ago

TI__Guru* 84915 points

Hi, Manjula,

The TLV320AIC3268 is able to be used with higher frequencies with the help of PurePath Studio. This software configures the internal miniDSP. So, more processing is allowed with it. Please take a look at the TI Design Guide for more information and let me know if you require something else:

www.ti.com/.../tiduan9.pdf

Best regards,
Luis Fernando Rodríguez S.

0 Manjula Ellepola over 8 years ago in reply to Luis Fernando Rodriguez S.

Expert 1335 points

Hi Luis

Thank you for the reply. According to the data sheet it says that decimation filter A is intended for 48 kHz and 96kHz. B is for 96kHz and C is specially designed for 192 kHz. Nowhere does it say that filter A or B could be used with 192kHz sampling. Can you confirm that by using PP studio/miniDSP it is possible to use decimation filter A or B with 192kHz to give a higher bandwidth than with C? If possible what are the drawbacks of using A or B with 192kHz?

Look forward to your reply.

Best regards
Manjula

0 Luis Fernando Rodriguez S. over 8 years ago in reply to Manjula Ellepola

TI__Guru* 84915 points

Hi, Manjula,

Exactly. PurePath Studio can configure the miniDSP in order to use the codec for ultrasonic applications. I only recommend to follow the indications of the TI Design Guide above.

Decimation filters A and B are specifically designed for applications with lower sampling rates. If these filters are used with a higher sampling rate, there could be lower performance.

Best regards,
Luis Fernando Rodríguez S.

0 Manjula Ellepola over 8 years ago in reply to Luis Fernando Rodriguez S.

Expert 1335 points

Hi Luis

Thank you for confirming. Has anyone tested the A or B filters with sampling rates as high as 192kHz and checked for performance?

If so can you let me know the results pls?

Thanks and best regards

Manjula

0 Luis Fernando Rodriguez S. over 8 years ago in reply to Manjula Ellepola

TI__Guru* 84915 points

Hi, Manjula,

Unfortunately, we cannot provide a performance result in this case since it may vary from application to application. Each application would have a determined performance based on the power supplies, layout design, output/input filters, etc.

I just recommend to follow the layout recommendations of datasheet. Additionally, I recommend to take a look at this wiki article for details about noise reduction:

e2e.ti.com/.../3377.common-noise-issues-in-codecs

Best regards,
Luis Fernando Rodríguez S.

0 Manjula Ellepola over 8 years ago in reply to Luis Fernando Rodriguez S.

Expert 1335 points

Hi Luis

I was asking specifically if anybody has experience or tried out using a high sampling rate (>96kHz) with the A or B decimation filters. If so what their experience was in terms of the noise or other issues. Has someone at TI tried this? I am not holding TI to the performance all I am after is that if it is use able with these settings.

Best regards
Manjula

0 Luis Fernando Rodriguez S. over 8 years ago in reply to Manjula Ellepola

TI__Guru* 84915 points

Hi, Manjula,

Basically, when a higher sampling rate is used with decimation filters A and B, the difference can be seen in the SNR level. The decimation filters A and B are designed to have the best SNR level at the specified frequencies. If higher frequencies are used, the SNR level would be reduced few dB.

Best regards,
Luis Fernando Rodríguez S.

0 Manjula Ellepola over 8 years ago in reply to Luis Fernando Rodriguez S.

Expert 1335 points

Hi Luis

Thanks for that. We will get an eval board and see what the performance is and if it fits our needs.
Thank you very much for your valued support and input.
Best regards
Manjula

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TLV320AIC3268: What is the use able frequency range?