• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 281 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.

TPS92518 ramp up time

Timothy Starr
Expert 2445 points
Other Parts Discussed in Thread: TPS92518

We are contemplating the use of the TPS92518 for a couple of new design. There will be two models:

-        2A Continuous, 5A Peak Pulse

-        4A Continuous, 10A Peak Pulse

Peak Pulses are less than 500 uS and will have a duty cycle of less than 1%.   The device needs analog current control andPWM control.  We’ll probably have a STM32F04x micro in the design for control.    There will be an external trigger signal that is used to initiate a current pulse.   Ideally the pulse latency  would be consistent and less than 10 us.    

Is there a way to keep the external MOSFET gate boot capacitor pre-loaded to assure that the ramp up time for the N-Type MOSFET drive doesn’t take too long? If so, how to accomplish? How fast will it be?

Thanks and Best Regards,

-Tim Starr on behalf of JF@MD/AI

  • 0
    TI__Intellectual 2590 points

    Tim,

    Please attach waveforms.  I am not sure I completely understand your application.

    In general, the rise time of a buck converter output current is controlled by the following relationship (Vin-Vout)/L which is the inductor current slope.  If the time constants are long, then that will govern your abaility to achieve10us rise time as the inductor current will be zero when you start.  I don't think the bootstrap capacitor will be the limitation, but if you show me your waveforms, then I can speak more confidently.

    -JP

  • 0 in reply to James Patterson
    Expert 2445 points

    Hi JP-

    We have no waveforms as this is a paper design at this point. We will be trying the eval board soon. We need less than the 10 uS latency…. Trigger to Output Current.   

    We think this can be done with the Shunt Bypass method, but we have a tiny package and Heat is NOT our friend. If we do have to use the Shunt Bypass approach then we were thinking about setting the Iadj current very low (keeping the boot strap cap filled) until the trigger signal and then increasing Iadj under hardware control.

    We'd love to have a concall regarding this issue, or continue the conversation via email. What do you think?

    Best Regards,

    -Tim Starr

  • 0 in reply to Timothy Starr
    TI__Intellectual 2590 points

    Tim,

    Let's take this one to email and we can go from there.  Closing this thread.

    -JP