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ADC/DAC combination with serial interface

Discussion in 'Embedded' started by Udo Piechottka, May 2, 2008.

  1. Hi there,

    i am looking for a compact solution with an ADC and a DAC that
    communicate without further "intelligent" interaction.

    The goal is to send a measured voltage over an optical link an to regain
    the analog voltage. (10..14 bit Resolution, DC...10/100kHz signal)

    Thanks - Udo
    Udo Piechottka, May 2, 2008
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  2. Udo Piechottka

    ghelbig Guest

    1st idea that pops into my head is the various I2S converters out
    there. Some go to 96KHz.

    Would be simple enough to take a A/D->I2S and connect it to an I2S->D/
    A, and that should do what you want.

    Disclaimer: I was way to lazy to do any part searches, let alone read
    any data sheets before responding.

    ghelbig, May 2, 2008
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  3. Those i found (ti, cirrus) are designed for audio transmission (low THD
    etc), the problem seems to be the total gain error (1..2% of fs) which
    doesn't matter in audio applications.

    Still searching - Udo
    Udo Piechottka, May 2, 2008
  4. Udo Piechottka

    rickman Guest

    You might find something around 10 bits of absolute accuracy, but it
    is hard to get much better than that. The reference that is used
    presents a limitation to the scale factor accuracy. To get better it
    would have to be trimmed and temperature compensated. I don't have
    exact numbers, but I can assure you that you won't find ADCs or DACs
    that will give you 14 bits of absolute accuracy.

    That said, there are a number of parts from TI and ADI that are
    designed for instrumentation with sample rates up to the MHz range.
    Some are sigma-delta converters which may not be DC accurate, I'm not
    sure. But I know there are a number of them that sample in the 100's
    of kHz range up to about 1 MHz that are successive approximation
    converters with 16 or even 18 bits of resolution. These will likely
    be about as good as you can find. A year to two back these parts were
    being heavily promoted since they were new parts then (or at least had
    new variants). I can't say how easy to use you will find their
    rickman, May 2, 2008
  5. Also verify the low frequency response, some chips intended for audio
    applications might have a low frequency limit in the 1-3 Hz range, so
    not useful if DC response is required. However, if you can perform
    analog voltage switching between a known reference voltage (ground)
    and the actual signal, this would solve this problem. With two or more
    reference levels, some linearity errors could be compensated at an
    expense of higher sampling frequency.

    As for interfacing to the fiber, you would have to combine the clock
    and data e.g. using Manchester coding and at the reception site a
    separation of clock and data would be required, such as in the SPDIF

    Paul Keinanen, May 3, 2008
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