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Current limit operation of TPS62175

Other Parts Discussed in Thread: TPS62175

We have questions about TPS62175.

Question 1.

Do you have the data about output characteristics of overload?

For example, waveform or graph of output voltage and output current in overload.

Question 2.

Output current keeps constant and output voltage drops in current limit operation.

Is this understanding correct?

Question 3.

We use TPS62175 and Load SW. 

       16Vin----------- TPS62175----------(5V)--------------Load SW

Inrush current(1A) occurs when soft-start is finished and Load SW enables.

This IC operates current limit and Vout drops.

Is there possibility that the time from starting current limit operation to recovering output voltage 5V fluctuates when load SW repeats turn-on and off at intervals of 15 seconds?

Please check the attached document.

Best regards,

Takahiro Nishizawa

3288.TPS62175.pdf

  • Hi Nishizawa-san,

    As noted in the current limit section in the D/S, please see figure 50 for an example of the current limit waveform.

    It sounds like the load switch does not have soft turn on?  This should reduce or eliminate the inrush current into the 220uF cap.  The other option is to add more output cap before the load switch.

    Since the source of the overcurrent event is a capacitor, and not DC, the IC will recover from the overcurrent and re-enter normal operation.  This is ok.  15 seconds is quite long and not an issue.

  • Thank you for your support!

    The load SW has soft-start.

    but our customer says  this has no effect.

    Do you know the cause of inrush current?

    Output capacitor of load SW?

    The time from starting current limit operation to recovering output voltage 5V is constant if the ON/OFF timing of load SW is constant.

    Is this understanding correct?

    Best regards,

    Takahiro Nishizawa

  • Hi Nishizawa-san,

    Please send a waveform (Vout of DC/DC, Vout of SW, current through SW, inductor current) of your issue.

  • Hello Nishizawa-san,

    Just a soft reminder.

    Please provide the waveform (Vout of DC/DC, Vout of SW, current through SW, inductor current) as requested in the previous post so we can address the query.

    Best regards,

    Excel

  • Thank you for your support!

    We want to cancel about waveform.

    We have new question.

    Question 1.

    Does the current limit threshold change by temperature?

    Does the current limit threshold increase if  temperature increases?

    Please tell us the relationship between threshold of current limit and temperature.

    Question 2.

    In datasheet p.9 8.3.3.Current limit and short circuit protection, you said 

    At heavy overloads the low-side MOSFET stays on until the inductor current returns to zero.

    current limit are 800mA(min) and 1200mA(max).

    Which is the shorter until the inductor current returns to zero?

    800mA to 0A

    1200mA to 0A

    Question 3.

    Please tell us the reason why current limit is changes(min 800mA~max 1200mA).

    Individual difference of  IC?

    temperature?

    other reason?

    Best regards,

    Takahiro Nishizawa

  • Thank you for your support!

    How is your situation?

    We hope earlier answer.

    Question 1.

    Does the current limit threshold change by temperature?

    Does the current limit threshold increase if  temperature increases?

    Please tell us the relationship between threshold of current limit and temperature.

    Question 2.

    In datasheet p.9 8.3.3.Current limit and short circuit protection, you said 

    At heavy overloads the low-side MOSFET stays on until the inductor current returns to zero.

    current limit are 800mA(min) and 1200mA(max).

    Which is the shorter until the inductor current returns to zero?

    800mA to 0A

    1200mA to 0A

    Question 3.

    Please tell us the reason why current limit is changes(min 800mA~max 1200mA).

    Individual difference of  IC?

    temperature?

    other reason?

    Best regards,

    Takahiro Nishizawa

  • Hello Nishizawa-san,

    Please see below response as highlighted.

    Q1. The current limit threshold is affected by temperature and typically it increases as the temperature rises.

    Q2. In case the current limit threshold shifts to 1200 mA, then it will take longer time for the inductor current to drop to zero in comparison with Ilimit threshold at 800mA.

    Q3. The current limit is affected by process and temperature variations.

    Best regards,

    Excel