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Original question:

TIDA-01513: TIDA-01513: Automotive High-Voltage and Isolation Leakage Measurements

TIDA-01513: PHYSICAL CHASSIS CONNECTION TO THE PCB BOARD

Yorly Walteros
Prodigy 75 points
Part Number: TIDA-01513
Other Parts Discussed in Thread: ISO7742-Q1, ADS8353-Q1, AMC1301

Hello,

In the schematic block diagram you put chassis connected to GND of 5V but from my understanding the Low voltage GND is different of the chassis of the EV (or at least it is the case in my system). I would like to know how to handle the fact that you're connecting the chassis of the EV to the GND of the low voltage system (5V) Please let me know,

Thanks for your help

  • 0
    TI__Expert 5120 points

    Yorly, hello and good day.  Your E2E query has been received and forwarded to the original design owner on our Automotive Systems team in Germany.  Please be advised that he is currently on holiday and will return to the office on Monday.  As is such, please give us 1-2 business days for the designer to receive and respond to your question. 

    Best Regards,

    John Fullilove

    Reference Design Operations

    Texas Instruments

  • 0
    TI__Prodigy 440 points

    Hello Walteros,

    Greetings,

    As per me, It is required in HEV / EV to measure the isolation leakage current from High Voltage Battery to Chassis ground.

    TIDA-01513 is built in such a way that low voltage ground is connected directly to chassis.

    In case if "low voltage ground" is different to chassis ground, then there is a different configuration to check the Isolation leakage current from High Voltage Battery to Chassis of HEV/EV.

    Let me know if there is a different understanding...

    Thanks

    Regards

    Rama

  • 0 in reply to Rama Chandra Reddy Kambham
    Prodigy 75 points

    Dear Rama

    I used the same configuration, just that the GND of the Isolation Measurement circuit is chassis for me, then I isolated these outputs (ISO_POS and ISO_NEG) to be connected to the ADC  of the microcontroller, Do you think is a good approach?

    Thanks a lot Rama

    Let me know

  • 0 in reply to Yorly Walteros
    TI__Prodigy 440 points

    Hello Walteros,

    Good to know that potential divider resistors are in between High Voltage Positive/Negative lines to Chassis Ground.

    I recommend to use a precision ADC (ADS8353-Q1)  to measure the ISO_POS and ISO_NEG and transfer digital data across isolation(Digital Isolator such as ISO7742-Q1 ). I prefer this approach due to less no of conversion losses.

    In case if you are looking for less no of components do check at isolated ADC's (such as AMC1305-Q1).

    Thanks

    Regards

    Rama

  • 0 in reply to Rama Chandra Reddy Kambham
    Prodigy 75 points

    Dear Rama

    Two questions:

    1. I am using the ADC of the my micro controller to measure iso_pos and iso_neg, I was trying to use and isolated amplifier like the AMC1301 and then single ended output but it seems it has some offset swing so it is probably a conversion loss issue.Do you think  that approach is  possible?

    2. I am simulating the calculation of the isolation resistance, and I calculated my RS1 and RS2 in order to have 0 ohms as my minimum resistance value, using the equations R_iso = (-Rs1*(HV_BATT+Vref))/(ISO_POS -Vref)-Rps1-Rps2 that you suggested in the forum but when i simulated using the TI i got an ISO_pos such that when i calculated it gives me a minimum value of 37.5K,Can you explain how to calibrate RS1 in order to have 0 ohms as minimum value.

    3. In case that I have two failures in HV_pos and HV_neg how the system  will proceeed, is using the same sequence?

    1. closing relay1 for iso_pos measurement 

    2. opening relay1

    3.closing relay 2 for iso_neg measurement

    Thanks Rama for your help

  • 0 in reply to Yorly Walteros
    TI__Prodigy 440 points

    Hello Walteros,

    I am closing the thread on e2e as we are in detail discussion privately.

    Thanks

    Regards

    Rama