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Original question:

TPS25925: Response time for current limit function

TPS25925: Response time of ILIM

Hideki Hayashi1
Expert 7600 points
Part Number: TPS25925

Hi team,

When Iload condition is ILIM<Iload<ISC, ILOAD will decrease to ILIM as my understands. And it is described in Figure 38.

How much time is required to decrease to ILIM? A customer have seen Iload>ILIM condition for 1.2ms. Is it the correct behavior?

Best regards,

Hayashi

  • 0
    TI__Guru 63995 points

    Hi Hayashi,

    Generally for eFuse it should be 400-500 us . But it does depend on amount of overload. Higher the overcurrent above current limit faster is the response time. I have to look at waveform to comment. I will recommend using a resistive load to test.

    1.What is the current limit setting customer using?

    2. How much load are they applying and how?

    3. Can you share the waveform showing VIN, VOUT and IIN like below zoomed in(us scale) to measure response time?

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Dear Kunal Goel,

    Thank you for your reply.
    I answer on behalf of Mr. Hayashi.

    1.What is the current limit setting customer using?
      -> Current limit Setting is 2.479A.(RILIM = 59.3kohm)

    2. How much load are they applying and how?
      -> The load is mobile phone CPU(SnapDragon).

    3. Can you share the waveform showing VIN, VOUT and IIN like below zoomed in(us scale) to measure response time?
      -> I have attached waveform material.

    Please let me know if the current waveform in the attached material is current limited.
    Also, I would like to know how to estimate the current pulse shape unaffected by the current limit.

    Best Regards,
    Hiroyasu Makino

    VIN, VOUT and Iin waveforms (400us scale).pptx

  • 0 in reply to Hiroyasu Makino
    TI__Guru 63995 points

    Hi Hiroyasu,

    It looks like device is allowing some overcurrent within response time and after response time it starts to limit.

    We have to also consider tolerance of current limit which is 10% and tolerance of current limit resistor also. Suppose in our case final tolerance is 11%. So ILIM max=1.1*2.5=2.75A. It could also happen that current is still below 2.75A threshold so device will not limit.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Dear Kunal,

    Thank you for your reply.

    If the final tolerance is 11%, should I be concerned about current limiting at ILIM_min=0.89*2.479=2.21A?
    In addition, please let me know if there is a way to allow current limit for pulse current.

    Best Regards,
    Hiroyasu Makino

  • 0 in reply to Hiroyasu Makino
    TI__Guru 63995 points

    Device will show tolerance in one direction either ILIM max or ILIM min. Within response time device will allow overcurrent.

    Please expect delay in my further responses. I am on leave till thursday.

    Regards

    Kunal Goel