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TPS25982: TPS25982 for Hotplug issue

Part Number: TPS25982
Other Parts Discussed in Thread: TPS650250, , TPS25980

Hi,

I am using TPS650250 in my design for 12V to 5V conversion. I will be connecting load across 5V. My load is SATA HDD. I will be connecting 3 SATA HDDs where each can consume maximum of 1.5A. But when I hotplug two SATA HDDs at the same time, my 5V output would fluctuate i.e my 5V regulator would turnoff and On within few milliseconds. This was due to the sudden inrush current 

We are going for R2.0 revision of the board and take care all these issues. Hence eFuse TPS25982 was suggested by TI expert. Can you please let me know TPS25982 will help me in solving this issue.

1. Let me know which is the part that i should select. Current limiter or current breaker part

2. Whether i should remove 5V regulator and use eFuse as alternate for that regulator?

3. Or I should connect the output from this 5V regulator as input to efuse and connect output of efuseto my SATA HDD?

3. Is it possible to give input of 5V and output of 5V

  • Hi Shifali,

    Thanks for reaching out. I will get back to you by tomorrow

    Regards

    Kunal Goel

  • Hi Shifali,

    TPS25982 will definitely help in achieving protection . Also you can check TPS25980 device which is a lower current  spin of TPS25982 and will offer cost advantage. 

    1. Current limit part will limit the current to load when there is overload but circuit breaker part will turn off the efuse when there is overload. So it depends on your load and application . If you want some critical read/write operation to happen you can allow limited current into HDD or if the HDD is sensitive to higher current than rated then you may want to turn off the supply to it. 

    2. Efuse can not be used as a regulator. It will give voltage at output which is same as input with some mV drop. Since HDD are rated for 5v ,you should give 5v input to eFuse.

    Regards

    Kunal Goel

  • Hi Kunal,

    Thankyou for your response.

    Kindly review the attached schematics.

    1. I have set the IILM=8A. Is the set value correct. As mentioned earlier my load is SATA HDD(x3).When these SATA HDDs are hotplugged I was facing voltage fluctuation issue. The SATA HDDs will consume maximum of 3A during read & write operation. But the inrush current during hotplug condition is not known. Hence I have set the ILIM=8A. Is the value correct. 


    2. What should be the recommended Vinmon if VIN=5V. Can we consider 3.3V.


    3 If Retry_delay=100ms ans Nretry=4, what does it mean.

    4. I have attached the complete schematics of efuse and SATA connectors. At the output of efuse I have connected a decoupling of just 0.1uF capacitor since the SATA connectors have lot of capacitors connected. Will lot of bulk capacitors cause any problem.

    5. The reference schematics has TVS diode connected to it. Is it mandatory in the design.

    6. How do I set the slew rate so that output v5482.DESIGN15.pdfoltage  does not dip.

  • Hi Shifali,

     Where are you placing efuse? On your power supply board or inside hard drive? You are using one efuse or 3 efuse for different hard drives?

    How much max current each hard drive can draw while in steady state operation?

    What is the current limit of your power supply?

    Regards

    Kunal Goel

  • Hi Kunal,

    I am placing efuse between my 5V regulator output and HDD connectors

    Each drive will consume maximum of 1A during steady state. Hence total 3 drives will consume 3A during steady state operation.

    By power supply do you mean 5V regulator. 5V regulator can source maximum of 12A. Currently I have designed it for 6A. 

  • Hi Shifali,

    1.Assuming your power supply can source upto 6A and maximum current requirement is 3A ,so current limit should be between these values as when overcurrent event happens we have to limit the current less than of what power supply is capable and also be able to supply required current to hard drives.

    2. VIMON max for 5V input can be considered 3.3V . If you are not using the pin you can leave it open

    3. Retry delay means that after part turns off due to  thermal shutdown then it will wait for this delay time to try to start again. Nretry means no of times part will try to restart after thermal shutdown. After no of retries are over then if thermal shutdown happens part will remain latched . Refer datsheet sections 8.3.4,8.4,8.3.3.3

    4. When efuse starts then you can adjust the value of CDVDT cap to control the inrush current through efuse. More the value of output cap more will be inrush current. You have to select CDVDT such that device has a successful startup . As CDVDT increases time to start efuse also increases 

    5. TVS is not mandatory. Please refer datasheet section 10.1 Transient Protection for  more details

    6. Please use our design calculator www.ti.com/.../TPS25982 to select CDVDT cap to adjust slew rate  based  on output cap value so that efuse has successful startup . 

    7. Please send the filled design calculator for schematic review.

    Regards

    Kunal Goel

  • Hi Shifali,

    Please keep us posted if you need any help here. Currently, I'm taking care this thread.