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TPSI2140-Q1: Insulation Resistance Measurement

Louis Huang
Prodigy 40 points
Part Number: TPSI2140-Q1
Other Parts Discussed in Thread: BQ79731-Q1, , BQ79631-Q1

Hello TI,

I would like to use the Battery V- reference architecture of TPSI2140 advance information for the 1000V BMS system for insulation resistance measurement.

I want to know the Battery V- architecture have any risk to damage or break the isolation the MCU when SW1 and/or SW2 toggles?

  • 0
    TI__Expert 5906 points

    Hello Louis,

    Let me get back to you on this tomorrow.

  • 0
    TI__Expert 5906 points

    Hello Louis,

    Thanks for checking with our team!

    To answer your question:

    • In this architecture, the MCU is referenced to HV- and is powered by an isolated power supply. 
    • Breaking isolation:
      • Turning on the switches breaks isolation - this connects a known resistance (R3, RDIV1, RDIV2) to the unknown resistance (RISOP, RISON) in order to measure it. 
      • Would this damage the MCU?
        • Depends on circuit and MCU
          • Some battery pack monitors have integrated protection circuitry (see BQ79731-Q1)
        • Without integrated protection, ADC can be damaged if RDIV1 shorts or if RDIV2 is open
        • Ways to mitigate risk:
          • Series of resistors for RDIV1
          • Resistors in parallel for RDIV2
          • Using Zener diode to clamp ADC voltage (may have leakage and affect ADC measurement accuracy)
      • Would this damage GPIO?
        • No, TPSI2140-Q1 has isolation barrier to prevent this.

    Let me know if this makes sense and if you have any further questions.

    Best regards,
    Tilden Chen

    Solid State Relays | Applications Engineer

  • 0 in reply to Tilden Chen
    Prodigy 40 points

    Hello Tilden,

    Thanks for your answered.

    Here is my architecture. Is this the same architecture as you mentioned?

    Another integrated protection circuitry should be BQ79631-Q1 not BQ79731-Q1?

  • +1 in reply to Louis Huang
    TI__Expert 5906 points

    Hello Louis,

    1. Yes, that is the same architecture as mentioned before.
    2. Regarding integrated circuitry protection, it would be best to check with that team but I think the BQ79631-Q1 does not have overcurrent protection while their upcoming BQ79731-Q1 does have overcurrent protection.

    Let me know if this makes sense and if you have further questions.

    Best regards,
    Tilden Chen

    Solid State Relays | Applications Engineer