• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 45 subscribers
  • Views 219 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ADS124S08: Data & Power isolator

Christian Beltrame
Prodigy 30 points
Part Number: ADS124S08
Other Parts Discussed in Thread: ADS1261, , ISOW7741, ISO7741

Hello,

I need to use a galvanic isolator with the ADS124S08 or ADS1261, for both power and SPI.

The ISOW7741 seems to be a really good option.

I need to use the EN_IO1 to put the SDO/MISO line in high impedance.

I am not absolutely sure that the disabled states for the SDI/MOSI and SCLK would be what the ADC would expect.

Would it be possible to combine the EN_IO1 and CS?

Do I need to use the ISOW-7741-F instead?

I would greatly appreciate your comments.

Regards,

Christian

  • +1
    TI__Guru** 113765 points

    Hi Christian,

    Take a look at this TI Design, Isolated, Transformerless, Bipolar Supply for 24-bit ADCs Reference Design.  This design is basically what you are trying to do.  You can easily make this a unipolar supply design as well.

    Best regards,

    Bob B

  • 0 in reply to Bob Benjamin
    Prodigy 30 points

    Thank you for the information.

    Using that reference design, particularly the ISO7741 side, would an active-high "pseudo CS" connected to the EN_IO1 while the INA (SPI /CS) is connected to ground be enough?

    Since the ISO7741 output is high when the input side is disabled, the /CS will follow the EN_IO1 going high.

    Do you see any subtle timing issue with that setup?

    I could avoid adding an inverter.

    Thank you for your help.

  • 0 in reply to Christian Beltrame
    TI__Guru** 113765 points

    Hi Christian,

    It is not totally clear as to what you are asking about.  The purpose of the inverter is to disable the EN1 when CS is high (off state) and enable when CS is low (active state).  The ADC is looking for a low on CS to enable the SPI interface.  I would just pull EN1 high all of the time and remove the inverter (and not connect to CS at all).  Another option would be to use a GPIO control signal if you want to use the EN1 to activate/deactivate the communication.

    Best regards,

    Bob B