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1kV DC isolation for Data and Power

Niels Koll
Expert 1950 points

Hello,

I am in need for an isolation solution that is capable to withstand 1kV (1000V) DC. In other words, the potential difference between the two isolated grounds can be up to 1000V.

For the signals, I need to access a slow ADC and a slow DAC on the isolated side. So it will end up in some LVCMOS/TTL signals to be isolated.

The isolated power supply has the following requirements:

  • 12V input voltage
  • 10V output voltage
  • 10W output power

Do you have any suggestions how to fulfill the 1000V DC isolation requirement?

I am looking forward to your answers.

Regards, Niels

  • 0
    TI__Intellectual 2325 points

    Hi Niels,

    Thank you for using our forums!

    Based on what you have said, I recommend we start with the ISO774X as a starting point for the discussion.

    • This is a digital isolator that is rated for 1414V DC working voltage per the standards.
    • It has 4 channels in total and we have variants in different forward/reverse channel configurations that you can choose from.
    • The datasheet is here : www.ti.com/.../sllsep4e.pdf

    Based on your channel count needed, we can go to a different part number : 776X ( 6 channels) or 772X ( 2 channels) and so on.

    • The spec I mentioned is in page 8, section 6.6. The parameter is labeled VIOWM (DC).
    • To maximize the pull Isolation high voltage potential of the IC, we recommend using the 16 pin -DW package version that is rated for 1414V.

    Now, do you have a simplified block diagram that could possibly share? We'd like to see how the power supply is partitioned.

    • For example, while the ISO rating across the barrier is 1414V, the local range on each half of the isolation barrier is < 5.5V .
    • That is, side 1 local signals and supply is < 5.5V w.r.t side 1 ground and side 2 local signals and supply are < 5.5V w.r.t side 2 ground.
    • Will you be stepping the 12V input voltage and 10V output voltages down to 5V or 3.3V to power the MCU, ADC/DACs and the Digital Isolator?
    • Also these parts can work between 2.25V - 5V supply for the LV signals. These have CMOS thresholds and can work up to 100Mbps.

    Please let us know what you think. If there are additional requirements or specs, we can iterate as needed and continue to help you. A block diagram would be helpful as mentioned.

    Hope this is useful
    Regards,
    Abhi

  • 0 in reply to Abhi Aarey
    Expert 1950 points
    Hi Abhi,
    thank you for dipping my nose on the ISO77xx devices. These are an excellent choise for my application.
    Lower voltage levels like 3.3V to power the ISO77xx are available, since there will be an FPGA on-board too.
    On the isolated side, I will place a small LDO or switching regulator to generate the rewuired 3.3V_ISO from the 10V_ISO. no problem.

    Do you also have an idea for the isolated 10V power supply?
    Do you have a recommendations which kind of isolated inductor I could use to achieve the 1000V DC isolation rating?

    Regards, Niels
  • 0 in reply to Niels Koll
    TI__Intellectual 2325 points

    Hi Niels,

    You are welcome, glad to hear about the other details, looks like it will be a good starting point !Low voltage signals on either side also look good - thanks for sharing the details.

    For the 10W isolated power supply case, we don't have a direct solution from our group [ISO], but we will include some helpful solutions links below and maybe our colleagues in the Power groups can help here:

    http://www.ti.com/tool/TIDA-00401

    http://www.ti.com/lit/ug/tidua78b/tidua78b.pdf

    Hope this helps.

    Regards,

    abhi

  • 0 in reply to Abhi Aarey
    TI__Mastermind 27105 points
    Hi Niels,

    It might be worthwhile to take a look at webench power designer to select a solution for your isolated 10W converter. This tool will suggest designs based on your careabouts such as solution size, BOM cost and efficiency:www.ti.com/.../webench-power-designer.html

    Here is one example of a possible solution for the 10W converter:webench.ti.com/.../SDP.cgi

    Best Regards,
    Ben Lough
  • 0 in reply to Abhi Aarey
    Expert 1950 points

    Hi all,

    thank you for your help.

    I will have a look into the Power groups now.

    Regards, Niels