• State TI Thinks Resolved
  • Locked Locked
  • Replies 2 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 186 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

LM5119: Low-side PWM operation problem in DCM mode

Seung-Ug Baek
Prodigy 10 points
Part Number: LM5119

Hello

We are looking for a solution to the problem that Low Side FET does not switch when operating with DCM. The output is normal, but the heat of the LOW side FET is a problem.

R and C of RAMP checked the datasheet and tried to change it, but it was not resolved.
(I tried setting RAMP C lower than 2nF.)


  • 0
    TI__Mastermind 26160 points

    Hello,

    I checked the waveform and looks normal in DCM mode. Is the lower power FET heat noticed only DCM mode? Is the lower power FET temperature looks OK in CCM mode?

    The lower power FET body diode is conducting the inductor current during OFF time. The FET body diode usually has higher voltage drop than the channel Rds/on.

    Please check the FET body diode forward voltage VF. You can calculate the lower FET power dissipation in both mode DCM and CCM. This tells you the power dissipation difference and the temperature rise may due to that.

    Regards 

  • 0 in reply to Mahmoud Harmouch
    TI__Mastermind 26160 points

    Hello,

    I did not receive an answer so I consider the issue is resolved and I'm closing the thread. Please let me know for further support

    Regards