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ISO1540: Isolation for EV2300

Daniel Cumbo
Prodigy 30 points
Part Number: ISO1540
Other Parts Discussed in Thread: EV2400

Hi,

We are trying to isolate the EV2300 SMBus by using the ISO1540. The circuit implemented is identical to the one in the ISO1540 datasheet (page 24). One side of the IC is being powered via the EV2300 board itself, whilst the other with an external 3.3 V supply. The problem is that no output is being observed on the ISO1540 when the EV2300 is transmitting. These is what we have done so far:

1) Tested the circuit with a function generator at the clock frequency of the EV2300. This worked perfectly.

2) Inserted a buffer between the EV2300 and the ISO1540. This also worked perfectly, but at the cost of bi-directional communication (which is useless).

The problem seems to arise when the EV2300 is connected directly to the ISO1540 (with the circuit explained above). Can you point me to the source of this problem and perhaps suggest a solution? 

Thank you and regards,

Daniel

  • 0
    TI__Mastermind 49485 points
    Hi Daniel,

    Sorry to hear that you are facing issues in using ISO1540 with EV2300. I have a few questions to understand your use-case better, please help me with your inputs.

    1. There is a note on EV2300 page which states that EV2300 does not work for 64-bit operating systems like Windows 7 and newer. Are you using a 32-bit operating system (like Windows Xp)? Did you also try using EV2400?

    2. Could you please let me know more details about the connections? Which side of ISO1540 did you connect to EV2300? Was it Side1 or Side2?
    What is connected to the other side of ISO1540?

    3. What are you using from EV2300 to power ISO1540? Is it VOUT (5V) or VCC (3.3V)?

    4. When you tested EV2300 by applying a clock from function generator, where did you apply the clock and where did you monitor it to check if everything works fine?

    Please help us with above inputs so that I understand the issue better. Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Prodigy 30 points

    Hi, thank you for your reply.


    1. I am using the EV2300 on Windows XP and do not own a EV2400. I can confirm that both the clock and data are present at the pins, checked with an oscilloscope.

    2. EV2300 is connected to side 2 of the ISO1540. The other side is connected to a BQ2084 chip.

    3. I am using the VCC (3.3V) pin to power the ISO1540 on side 2.

    4. I applied the clock to side 2, on both data and clock pins. The output was monitored on side 1 - with an oscilloscope.

    Thank you again.

    Regards,
    Daniel

  • 0 in reply to Daniel Cumbo
    TI__Mastermind 49485 points
    Hi Daniel,

    Thanks for sharing your inputs.
    I have checked the logic thresholds for bq2084 and I see that it is compatible with ISO1540's Side1. Hence they are expected to work fine.

    Can you please confirm that the connection between ISO1540 and bq2084 is short? Are they both on the same PCB?

    If you bypass ISO1540 and short the connections making it non-isolated, do you see bq2084 communicating with PC?


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    TI__Mastermind 49485 points
    Hi Daniel,

    Will you be able to share any update you have on the issue? Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Prodigy 30 points
    Hi - thank you and sorry for not replying earlier,

    No, they are not on the same PCB and they are connected via jumpers. The system works fine when bypassing the ISO1540. I will try shorten the jumpers as much as possible and get back to you.

    Unfortunately, I had to put the project on hold due to other commitments, but will resume shortly.

    Regards,
    Daniel
  • 0 in reply to Daniel Cumbo
    TI__Mastermind 49485 points
    Hi Daniel,

    Thanks for the update. Glad to know that you will be looking into shortening the distance between ISO1540 & bq2084.

    Since you will be looking into this project at a later time, I will go ahead mark this E2E post as closed for now for ease of tracking open E2E posts. Once you have an update, you can either respond to this E2E post or create a new E2E post by clicking on "Ask a related question". Thanks.


    Regards,
    Koteshwar Rao