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TMCS1123: Maximum current of TMCS1123

Kento Adachi
Intellectual 1495 points
Part Number: TMCS1123

Tool/software:

Hello experts,

I got a few questions from a customer regarding TMCS1123 maximum current.

1.The Ambient Temperature in Figure 7-4 excludes self-heating effect, that is, the ambient temperature is case temerature without self heating? 


2. If the maximum continuous current in Figure 7-4 is exceeded, will the product fail even if the operating temperature range is not exceeded? I believe if we use a board with higher heat dissipation ability than the EVM, we can exceed the max current shown in the image.


3. In the event of a failure by exceedeing the max continuous current, what failure mode is expected?

  • 0
    TI__Intellectual 2715 points

    Hi Kento,

    1. You are correct. The figure refers to the Ambient Temperature in the case without self heating. You want to make sure that you follow this guide for measuring the precise temperature of the TMCS1123: https://www.ti.com/lit/an/sboa400/sboa400.pdf 

    2. Yes, the device will obey the curve of Figure 7-4 and will fail if the current is exceeded at a given temperature. If you use a board with higher heat dissipation or active cooling you may be able to increase the SOA.

    3. If you exceed maximum continuous current you will damage the device. This could involve internal warping/fusing of the lead frame or, in extreme cases, you will see external damage to the device.

    Regards,

    Holly Roper

  • 0 in reply to Holly R
    TI__Intellectual 1495 points

    Hello Holly,

    Thank you for the immediate response.

    Let me confirm one point about Q.2.

    If we use a board with higher heat dissipation or active cooling to increase the SOA, how can we calculate the increased SOA?

    Should we only consider the max junction temperature, thermal resistance, and heat dissipation? or, do we have other criteria which we should comply with?

    Thanks,

    Kento

  • +1 in reply to Kento Adachi
    TI__Intellectual 2715 points

    Kento,

    I will give you an example of what I mean when I say that active cooling can increase the SOA. The curve is fixed, but let's say the ambient temperature is 75°C (the blue line); if you have active cooling that drops the internal temperature 25°C, your new operating point is then 50°C (purple line). The active cooling allows you to then have a maximum current of 74A at 75°C  rather than the original 65A. 

    In summary, active cooling allows you to shift the curve to the right.

    Max junction temperature, thermal resistance, and heat dissipation are the three main factors, but ultimately you will not be changing the curve. Please refer to the guide sent earlier to make sure you are getting precise temperature measurements.

    I hope this helps.

    Regards,

    Holly