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TMCS1107: Safety limiting values

Austin Do
Expert 3335 points
Part Number: TMCS1107
Other Parts Discussed in Thread: TMCS1126

Tool/software:

Hello team,

What is the safety limiting value?

Side 1 and 2 mean two area separated by isolation barrier. Is this correct?

If yes, TMCS1107A1U should sense the current up to 55A, but limited by 30A from safety limiting.

Please clarify this and let me know if my understanding is wrong.

Best regards,

Austin

  • 0
    TI__Genius 17360 points

    Hello Austin, 

    Thank you for your post. 

    Safety refers to ratings for the device that should not be exceeded to prevent the internal isolation of the device from getting damaged.

    This leads to your next question about the sides of the device. You are correct with your understanding of side 1 and side 2.

    Side 1 is the high voltage side and side 2 is the low voltage circuitry to provide the amplifier output of the current flowing through IN+ and IN-

    The internal isolation of the TMCS1107 adheres to the below specs:

    I believe you are also on the right track for the current rating. Basically, in the footnote of table 5-1, it states that while some device variants have gains suitable for 50A transient current, the maximum RMS current from the safety operating area curve must be adhered to.

    I hope this helps!

    Best Regards, 

    Joe

  • 0 in reply to Joe Vanacore
    TI__Expert 3335 points

    The customer is supposed to report maximum current rating for TMCS1107A1U. So we need exact value for this device variant. Can you check this? The customer will sense current up to 53A.

    Best Regards,

    Austin

  • 0 in reply to Austin Do
    TI__Genius 17360 points

    Hello Austin, 

    If this application has a continuous RMS current outside of the SOA curve then this device will not be able to support the application.

    Can you please describe the waveform that your customer is trying to measure?

    Is it a continuous 53A RMS current?

    Is the 53A only for a short period of time?

    What is the ambient temperature of their system?

    Best Regards, 

    Joe

  • 0 in reply to Joe Vanacore
    TI__Expert 3335 points

    Hi Joe,

    It is not AC current. The customer said that normally 46A continuous current is expected. 53A is peak current. So, 53A is short period time. 

    Anyway, TMCS1107A1U has different SOA curve. Is this correct?

    Best Regards,

    Austin

  • 0 in reply to Austin Do
    TI__Genius 17360 points

    Hello Austin, 

    Since the 46A operating condition is exceeding the TMCS1107 30ARMS current SOA curve, I would suggest you look at the TMCS1126. 

    The TMCS1126 will be able to operate in your system and I have attached the SOA curve for this device below:

    Here is the link to the automotive datasheet for the TMCS1126: https://www.ti.com/lit/ds/symlink/tmcs1126-q1.pdf 

    Here is the link to the commercial product folder: https://www.ti.com/product/TMCS1126 

    Best Regards, 

    Joe

  • 0 in reply to Joe Vanacore
    TI__Expert 3335 points

    Hi Joe, 

    Thanks for suggestion. Let me suggest this to the customer.

    However, what is the exact meaning Iin Linear measurement range of TMCS1107A1U? It is confusing the customer select the parts. 

    Best Regards,

    Austin

  • 0 in reply to Austin Do
    TI__Genius 17360 points

    Hello Austin, 

    Good question. The linear measurement range is where the input is proportionally amplified by the sensitivity. 

    Outside of this range, the device will rail or saturate to the positive or negative rail. So you can think of the linear measurement range as the measurement range of the device that cannot be exceeded with accurate measurement results. 

    Best Regards, 

    Joe