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TPS61099: Inrush Current

Jan Kohli
Prodigy 20 points
Part Number: TPS61099

Hi

I'm using a TPS610993 converter in my circuit and have some issues with the inrush current.



As soon as I enable the converter there is an inrush current spike around 100mA for about 3ms. I also tried to decrease C8 to 100nF to see if the capacitive load is too high and causes this inrush current spike. However, C8 should be at least 10uF as it's written down in the data sheet for a stable voltage output. Is it somehow possible to cut off these spikes? I need them to be below 15mA. Is there another type with better performance to get 3V out of 1.2V with a typical current load of 10mA.

  • 0
    TI__Mastermind 34201 points

    Hi Jan,

    The expert supporting this device is on business travel. He will reply you as soon as possible.

  • 0
    TI__Mastermind 46905 points

    Hi Jan,

    it is normal behavior during startup, the device requires such current to charge the output capacitor.

    the only solution is to reduce the output capacitor and increase the input capacitor. but the output ripple will be larger with smaller output capacitor. that is something you need to balance. 

  • 0 in reply to Jasper Li
    Prodigy 20 points

    Hi Jasper

    Thanks for reply. That's exactly what I tried. Unfortunately I could not figure out a usable setup with these modified capacitors. The Inrush current is always higher than 15mA. So I have a general boost converter problem where I may need to find another power supply solution. Could you recommend another low power and small sized converter?

    I need 3V (or 3.3V) out of min. 1.0V Input. Typical load is 2mA, max load is 10mA. An of course no inrush current spikes higher than 15mA.

    Best Regards Jan

  • 0 in reply to Jan Kohli
    TI__Mastermind 21565 points

    Hi Jan:

    So sorry that I'm in oversea travel these days. Please allow me reply next Monday. Thanks for your patient waiting.

  • 0 in reply to Jan Kohli
    TI__Mastermind 21565 points

    Hi Jan:

    Thanks for you kind patience.

    It's really hard to make the irush current below to 15mA. May I know why it's 15mA? For your system, the load current could reach to 10mA. Take efficiency=80% as example, Iin(avg)=Io*Vo/Vin/Eff=15mA*3.3V/1V/0.8= 56mA. 

    As Jasper suggested, reduce the output capacitor and increase the input capacitor can help to reduce inrush current. But i don't think the inrush current should be less than the input current during normal operation.

  • 0 in reply to Minqiu Xie
    TI__Mastermind 21565 points

    Hi Jan:

    As long time not hear you, I assume you have solved the issue. I'll close this post.

    If not, just reply below. Thank you~