• State Resolved
  • Locked Locked
  • Replies 5 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 282 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS61099: SW current limit

Brian Antheunisse
Expert 5305 points
Part Number: TPS61099

Hi guys,

My customer has a worst case spec of 2.8Vin, 3.8Vout @ 450mA. I calculated that the SW current would be ~.89A which is greater than the min spec in the datasheet of .8A. 

Should we choose another part? any recommendations?

Thanks,

Brian

  • 0
    TI__Mastermind 21565 points

    Hi Brain:
    Do you have other spec requirements?
    Maybe the TPS61021 is Ok for you.

  • 0 in reply to Minqiu Xie
    TI__Expert 5305 points

    More than anything I need 100% confirmation that that part is truly not ok for that spec. Webench doesn’t give me an error, but when I calculate it, it’s right on the cusp.

  • 0 in reply to Brian Antheunisse
    TI__Mastermind 21565 points
    Hi Brian:
    We could only recommended the application within the spec.
    Let do an easy calculation, and set the efficiency is 90%
    Iin_avg=3.8*450/0.9/2.8=678mA, Ipeak=Iin_avg+150mA=828mA, higher than the spec.

    Do you know the efficiency of the worst case?
  • 0 in reply to Minqiu Xie
    TI__Expert 5305 points

    According to the graphs in the datasheet, the efficiency looks to be worse than 90%, so we probably need to find an alternative device. I am worried that we will lose this socket though, as my customer has scoured our portfolio already.

    Maybe you guys can give the best recommendation, here is the rest of their spec:

    The criteria I’m hoping to meet are:

    • 75+% efficiency at loads as low as ~10uA
    • Load connected to this regulator would vary from ~3uA to ~450mA
    • “Ultra-low” IQ
    • Capability of being able to output 3.8V at ~450mA from a battery whose voltage ranges from 2.8 – 3.6V.

    The maximum load current of 447mA only happens for very short bursts, but I suspect that doesn't matter, if we breach the spec, we don't recommend it. 

    Again, Webench doesnt seem to give an error, which makes me nervous about trusting it in the future. 

    Thanks,

    Brian 

  • 0 in reply to Brian Antheunisse
    TI__Mastermind 21565 points
    Hi Brian:
    Got it. I'll close this post firstly and contact you with E-mail.