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Precision ADC with I2C interface

fabricepeden
Intellectual 495 points
Other Parts Discussed in Thread: ADS1115, ADC128D818, ADS7828, AMC7812, ADS7844

Hi everybody,

I'm looking for an ADC with I2C interface. I thought that it was very easy, so I found some references on TI website but, I have the same problem at each time, there is only two addresses pins.

On my application, I need to have 5 ADC of 8 channels. Or with only two addresses pin, I can use only 4 devices. I have found among other competitors some references that use high impedance state to provide more addresses.

Do you know if there are references among TI which have at least this characteristic ?

Thank you in advance,

Regards,

Fabrice Péden

  • 0
    TI__Mastermind 22815 points
    Hi Fabrice,

    do you have any specific requirements regarding the ADC resolution, data rate, performance, etc?
    The ADS1115 for example is a nice little 16-bit ADC that offers up to 4 analog inputs. It only has a single address pin, but the pin has four states. Means you could operate up to four of those ADS1115 on a single I2C bus. This would give you up to 16 analog inputs then.

    Regards,
  • 0 in reply to Joachim Wuerker
    Intellectual 495 points

    Hi Joachim,

    Thank you forr your answer. I have no specific requirements (except the resolution that must be at least 12 bits).

    But I need at least the possibilty to have 5 I2C slaves as shown below.

    Regards,

    Fabrice Péden

  • 0 in reply to fabricepeden
    TI__Mastermind 22815 points
    Hi Fabrice,

    I am sorry, I guess I misunderstood your requirements then. I thought you need overall 8 channels. But seems like you need overall 40 channels.
    I don't know of any solution from the Delta-Sigma ADC portfolio in that case, but maybe my colleagues from the SAR ADCs have something to offer.

    Regards,
  • 0 in reply to Joachim Wuerker
    Intellectual 495 points
    Hi Joachim,

    Thank for your answer. How can I contact your colleagues ?

    Regards,

    Fabrice Péden
  • 0 in reply to fabricepeden
    TI__Mastermind 22815 points
    Hi Fabrice,

    they are following this forum as well and will respond here if they know of a solution.

    Regards,
  • 0 in reply to Joachim Wuerker
    Intellectual 495 points
    Hi Joachim,

    I found this reference : ADC128D818 that, I think, can correspond to my need.

    12 bits of resolution, up to 9 devices on the same bus, 8 channels the sample rate is very low (82 SPS).

    Regards,

    Fabrice Péden
  • 0 in reply to fabricepeden
    TI__Intellectual 1205 points

    Hello Fabrice Péden:

    You are right:  the ADC128D818 has 8 channels and two tri-level address pins, which will allow you to have more than 5 devices on a single I2C bus.  Another option is the ADS7828, which has 8 multiplexed channels, but is limited to only 4 devices per I2C bus because it only has two address pins.

    Have you considered an AMC7812?  This is an Analog Monitoring and Control chip with 16 single-ended ADC channels, an I2C interface, and three address pins.  This would allow you to have up to 8 on a single bus, with 16 channels each.  This chip also has DAC's, temperature sensors, GPIO pins, alarms, and other things.  You might find it useful to program the alarm registers, set the device to automatic monitoring mode, and read the data via I2C only if an out-of-range condition is detected.

  • 0 in reply to Bryan McKay
    TI__Expert 8630 points

    Hello Fabrice,

    Can you please share few more requirements below for the 8Channel ADC with I2C Interface?

    • Analog Input Range for the ADC.
    • Aggregate sampling rate for 8 Channels.
    • Are there any amplifiers driving the analog input of the ADCs
    • Tentative Samples Requirement Date/Timelines.

    Thanks,

    -Lokesh

  • 0 in reply to Lokesh Ghulyani
    Intellectual 495 points

    Hello Bryan and Lokesh,

    Bryan, concerning the AMC7812, I have found it, but I think it's a little bit complex and expensive for our application.

    Lokesh, in input I'll use this design (https://e2e.ti.com/support/amplifiers/etc_amplifiers__other_linear/f/18/t/543472) that I've validated with one of your engineers. So input range will be between 0 and 3V3.

    Concerning the sample rate, I don't really know, because my measure consists by measuring 0/10V or 4/20mA, so I don't know what is the minimum/best sample rate for this kind of measure.

    I hope my explanations are enough clear.

    Regards,

    Fabrice Péden

  • 0 in reply to fabricepeden
    Intellectual 495 points
    Hello everybody,

    I think I have found another solution.

    I can use the following reference (ADS7844 from TI) which uses SPI interface and an I2C/SPI converter (as the following SC18IS602B - maybe TI provides this kind of device ?) which allows easily to have several addresses on my I2C bus.

    Regards,

    Fabrice Péden