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TPS2051B: Load Capacitance

Koichi Nonomura
Prodigy 45 points
Part Number: TPS2051B
Other Parts Discussed in Thread: TPS2051,

Hello

I saw TPS2051 TI document sheet-23 figure-39 for about inrush current with different load capacitance as the file attached. 

Could you advise me what maximum spec of capacitance? And if it exceeds, will it drive to be in overcurrent condition / overtemperature shutdown? 

 

  • 0
    TI__Mastermind 18031 points

    Hi Koichi,

    For hub application, it requires no less than 120uF.

    For others, it's according to customer's application.

    If it's too big, power switch may response very quickly and shut down then restart.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Ziv san, Thank you very much for quick reply.

    Just let me know what you mean "hub application".

    I am using TPS2051B for one port USB power supply switch. Is this "hub application"?

  • 0 in reply to Koichi Nonomura
    TI__Mastermind 18031 points

    If just usb then application device, I think it’s not hub application.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Thanks. BTW, is there any SPEC of max capacitance even hub appli?

    If TI documented such SPEC, please share me web link.

    Also, in case of too big capacitance, how power switch responds quickly and shut down then restart? Is that detected by current or thermal then OC?

    Please explain more detail.  

  • 0 in reply to Koichi Nonomura
    TI__Mastermind 18031 points

    Please check USB2.0 specification on page 179.

    As start up, it needs to charge the cap. With bigger cap, the charging current is bigger.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Ziv-san, Thanks a lot. I understand TPS2051 complies USB 2.0.

    Would you reply another question in my message earlier? "Also, in case of too big capacitance, how power switch responds quickly and shut down then restart? Is that detected by current or thermal then OC?"

    I feel sorry for many questions, but appreciate your attention.

  • 0 in reply to Koichi Nonomura
    TI__Mastermind 18031 points

    Sorry for the confusing Kochi.

    In fact, as insert big cap, such as hard disk, power switch need to charge the cap with high transient current. The power switch will limit the current. But as the transient current is too high, the current limit loop respond very quickly and turn off the gate and then restart the power switch.

    But for the output cap default, I check the USB2.0 spec, but can't find the cap limitation.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Ziv-san, Thanks again for your support.

    I could understand your comment, but as I see TI SPEC in-rush current chart attached, regardless capacitance value, the rise time is same and peak current is forced current limit as 1A for TPS2051. I was just confused.

    If the case capacitance is too big as 0.1F, what happen? Is peak current higher than 1A? Please advise.

  • 0 in reply to Koichi Nonomura
    TI__Mastermind 18031 points

    Hi Kochi,

    As I mentioned before, the inrush current is happened as cap is attached first, then power on. But the other scenario is as the power is on, then attach big cap such as hard disk, it will surpass the current limit value.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Hello Ziv-san.

    I want to know inrush current limitation. Please let me know the case of 0.1F load cap. 

  • 0 in reply to Koichi Nonomura
    TI__Mastermind 18031 points

    Hi Koichi,

    Please contact the FAE who is responsible for your company. And send the request to BU.

    Thanks.

    For TI's policy, I will first click resolved button.

    If you have any other concern, contact me any time.

    If you think resolved, please help click 'Issue is solved button'.

    Thanks.

  • 0 in reply to Ziv Zhang
    Prodigy 45 points

    Ziv-san, Thanks for your support. I will contact FAE on this.