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TLV320ADC6140: Frequency response for 4 channels

Alessandra Fusco
Prodigy 50 points
Part Number: TLV320ADC6140

Planning of using LV320ADC6140 - for an evaluation board. According to datasheet, 80kHz bandwidth is expected. But experimental measurements revealed that only with 2 channels and proper filter settings, we get closer to a flat response (green line below). Otherwise, 4 channels revealed a response as the one in red.

Please provide settings in order to obtain same bandwidth as stated in the datasheet.

  • 0
    TI__Mastermind 23050 points

    Hi Alessandra, 

    It looks like your attachment did not come through. Can you try reposting in a different format? 

    The number of supported channels will depend on the sample rate you are running at and the features you intend to use. You may want to take a look at this app note that describes the supported blocks for various sample rates. https://www.ti.com/lit/an/sbaa381/sbaa381.pdf?ts=1596651578090&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FTLV320ADC6140

    Best,

    Zak

  • 0 in reply to Alessandra Fusco
    Prodigy 50 points

    From the document you forwarded, 192kHz sampling rate only support linear phase decimation filter for 4 channels. Unfortunately the linear phase filter, decays very early, limiting the bandwidth of our signal.

    Is there any other way of getting 80kHz bandwidth with 4 channels?

    Thank you in advance!

    Alessandra

  • 0 in reply to Alessandra Fusco
    TI__Mastermind 23050 points

    Hi Alessandra,

    Unfortunately the linear phase filter is the only filter supported at 192kHz if you need for channels. These devices were designed for audio applications and the increased sample rate support is primarily to reduce latency rather than increase the input bandwidth. You could potentially use two devices operating at 192kHz and then use one of the low latency filters, which won't roll of until closer to 85kHz, but there is not a way to do this with 4 channels on a single device.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Prodigy 50 points

    Hi Zak,

    Thank you a lot for clarifying. As precautionary measure, we added indeed a second ADC in order to ensure the larger BW but I was still hoping in a workaround.

    Any alternative product you would suggest in order to reach our scope with a single ADC?

    Best,

    Alessandra

  • 0 in reply to Alessandra Fusco
    TI__Mastermind 23050 points

    Hey Alessandra,

    Is this for an ultrasound sensor such as occupancy detection? If you are limited to using audio ADCs with an I2S/TDM interface then I don't think we have any single ADC solutions, but we do have plenty of non-audio ADCs with SPI interfaces that could likely satisfy your bandwidth requirements depending on the other specs you have in mind.

    Best,

    Zak

  • 0 in reply to Zak Kaye
    Prodigy 50 points

    Hello Zak,

    Understood. We capture audio as well, so audio ADCs with I2S/TMD interface was the logical solution. Any examples of these non-audio ADCs you can share? Multichannel, ~90kHz bandwidth. A plus of TLV320ADC6140 is that it worked for both analog and digital microphones.

    Regards,

    Alessandra

  • 0 in reply to Alessandra Fusco
    TI__Mastermind 23050 points

    Hi Alessandra,

    Any products outside of the audio portfolio are not going to support digital microphone inputs, so if you need that flexibility then ADC6140 is probably still your best option. Admittedly I am not as well versed in our non-audio ADC products, but it depends on what kind of performance you need. I believe anything operating at >180kHz sample rates is going to be a SAR ADC architecture, whereas all of our audio ADCs are delta-sigma architectures to support the standard 16-32 bit audio formats. Some things I would ask:

    • What resolution do you need? 
    • Do you need simultaneous sampling or is a muxed architecture okay? Note with muxing the inputs to have 90kHz bandwidth on each channel you would need a converter that can run up to 720ksps so that may be a limiting factor.
    • Any other system constraints? i.e. size, power consumption, etc.

    From what you've described thus far I think 2x ADC6140 works the best, but if you don't require audio formatting and can use a SAR architecture with somewhat lower resolution then there may be some other options!

    Best,

    Zak