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TPSI2140-Q1: How select RisoP RisoN

user5883945
Expert 1321 points
Part Number: TPSI2140-Q1
Other Parts Discussed in Thread: TIDA-010232, , TPSI2072-Q1

Hi,

  Customer refer design Guide: TIDA-010232 to insulation Monitoring, they system voltage need 1500Vdc max, but the design is for 400Vdc system,

Do you have an idea to choose the suitable RisoP RisoN, the equation is to complex.

customer's design exactly same with reference design.

  • 0
    TI__Prodigy 486 points

    Hi,

     

    This design followed the recommendations laid out in the standard IEC/EN 61557-8 & IEC 61851-23 where:

    Riso Warning

    500 Ohms/V

    Riso Error

    100 Ohms/V

     

    So for 1500V, the resistances to give the warning needs to be 750kOhms and for the error signal it is 150kOhms.

     

    Let me know if you have any more questions!

    Thanks,

    Sam Skranak

    Product Marketing & Applications | Solid-state relays

  • 0 in reply to Samuel Skranak
    Expert 1321 points

    Hi，

      Based on this, our board same with TIDA-010232, but the voltage is 1500dc, how can we chose the resistance value for RstP and RstN, thank you!

  • 0 in reply to user5883945
    TI__Prodigy 486 points

    Hi,

    I will need some extra time to analyze this. Myself or a member of my team will get back to you on this soon.

    Thanks,

    Sam

  • 0 in reply to Samuel Skranak
    Expert 1321 points

    Hi,

        thank you! The equation is more difficult for us and looking forward for your feedback.

  • 0 in reply to user5883945
    TI__Prodigy 486 points

    Hi,

     

    Based on my analysis of this so far, the reference design cannot be copied exactly since the TPSI2140-Q1 is not able to withstand 1500V without breaking down. There are some alternatives however:

    1. Use TPSI2140-Q1 in parallel with a resistor that divides down the voltage but has a constant leakage current.
    2. Use 2x TPSI2140-Q1 and 1x TPSI2072-Q1 to ensure up to 1800V breakdown voltage.

     

    The two options are drawn out below.

     

    To reiterate, because of the 1200V breakdown of TPSI2140-Q1, the design cannot be copied exactly. I will meet with my team to make sure there aren't other alternatives.

     

    Let me know your thoughts!

    Thanks,

    Sam Skranak

    Product Marketing & Applications | Solid-state relays

  • 0 in reply to Samuel Skranak
    Expert 1321 points

    Hi ,

      The datasheet describe the working voltage can up 1500-DC, could you help to confirm it.

       And help us to choose resistance value for RstP and RstN if the working voltage maxim is 1200V;

    thanks you!

  • 0 in reply to user5883945
    TI__Prodigy 486 points

    Hi,

    The 1500V voltage is the isolation working voltage between the primary and secondary sides. So the device can withstand up 1500 between the VDD pin and S1 pin, not S1 and S2.

     

    For the resistances, I am using a tool to calculate what values have the least error at 1200V. It is available here if you would like to work with it as well: https://www.ti.com/tool/TIDA-010232#start-development

    Just be sure to change the voltage to 1200V and raise the max power dissipation or Rst count.

     

     

    When I input Rst = 700kOhms, we have errors that hover around 5% min and max. This is a good starting point for the design. Keep in mind that Rst must be greater than the warning resistance.

    Another thing to think about is if the customer is going to conduct a withstand voltage, or high potential, test. If the test voltage is high enough that it drives more than 1 mA of current through the TPSI2140-Q1 in breakdown, then Rst must be sized larger to reduce the current.

     

    Thanks,

    Sam Skranak

    Product Marketing & Applications | Solid-state relays