ADC/DAC combination with serial interface

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

On May 2, 10:10 am, Udo Piechottka <ifmd.messdatensyst...@t-online.de>
wrote:
> 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

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.

G.

schrieb:
> 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.

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

On May 2, 3:58 pm, Udo Piechottka <ifmd.messdatensyst...@t-online.de>
wrote:
> ghel...@lycos.com schrieb:
>
> > 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.
>
> 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

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
interfaces.

On Fri, 02 May 2008 21:58:04 +0200, Udo Piechottka
<> wrote:

> schrieb:
>> 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.
>
>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

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
system.

Paul