• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 46 subscribers
  • Views 223 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

ADS130E08: Isolation of SPI bus

Danilo A.
Mastermind 26890 points
Part Number: ADS130E08
Other Parts Discussed in Thread: ISO7731

Hi Team,

Our customer would like to know when to isolate the SPI bus of ADS130E08 from the microcontroller? He also wants to know if TVS diodes on ADC inputs are enough to stop EFTs and ESDs?

Regards,

Danilo

  • 0
    TI__Mastermind 18900 points

    Hi Danilo,

    Sorry for the delay:

    Danilo A. said:
    Our customer would like to know when to isolate the SPI bus of ADS130E08 from the microcontroller?

    I'm not super knowledgeable about this but it relies heavily on what the system or applicable is. In 3 phase metering, which is a specialty for the ADS130E08, you'll always need isolation. Another tell-tale sign is if the application has to interact with some IEC standard or something else. The more practical is, "if a wire is crossed, can someone be seriously injured". In addition, the isolation barrier can be in many places: the front end, the ADC, the modulator, the MCU, etc.

    To be a bit more concrete, take a look at this reference design for the ADS131M0x, newer and similar generation to the ADS130E0x. https://www.ti.com/tool/TIDA-010037 You can find that we rely on the current transformers for current measurements but still have an ISO7731 on the UART lines. 

    We even have ones like the https://www.ti.com/tool/TIDA-00555 where the isolation barrier in the differential amplifier. There's also isolated modulators if you want to completely change the topology.

    Danilo A. said:
    He also wants to know if TVS diodes on ADC inputs are enough to stop EFTs and ESDs?

    Yes, they are enough to stop EFT and ESD. Please take a look at this app note for more information on the importance of putting TVS diodes, and other devices, on the input to help with those scenarios:  https://www.ti.com/lit/pdf/sbaa548 

    Here's a whole lot of other material you might find interesting:

    Best,

    -Cole

  • 0 in reply to Cole Macias
    TI__Mastermind 26890 points

    Hi Cole,

    Thank you for your comments. Please see the feedback of our customer below.

    I admit I was vague and this will have given you work, I need a little to read everything.
    Let me explain: I have a microcontroller that communicates with a differential ADS, via SPI bus. ADS measures the differential signal coming from a stress cell located about one / two meters from the board. The stress cell measures the deformation of an object.The chip I want to use is ADS130E08IPAG and TMS320F28004x-100pins

    from what I understand TVS diode would be enough to protect the two chips. Correct me if I'm wrong please.
    I will try to read all files as soon as possible, I really appreciate the ideas you gave me

    Regards,

    Danilo

  • +1 in reply to Danilo A.
    TI__Mastermind 18900 points

    Hi Danilo,

    Danilo A. said:
    ADS measures the differential signal coming from a stress cell located about one / two meters from the board. The stress cell measures the deformation of an object.

    Assuming there's nothing hazardous about the voltage or current running over the lines to the ADC, I don't see a reason for isolation. Only other reason I can think of if you think the ground loop is going to be too noisy for a micro controller then maybe you can attempt to isolate but you'll have a much better time attempting to use good layout technique to ensure noise doesn't affect the MCU.

    Danilo A. said:
    from what I understand TVS diode would be enough to protect the two chips. Correct me if I'm wrong please.

    Because ESD and EFTs need to come from some interaction with the environment, those cables and the inputs will be the primary way for energy to get into the system. So, diodes on the input will help you tremendously there.

    No problem! Enjoy the material.

    Best,

    -Cole