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Original question:

LM5117: Design review

LM5117: High Power dissipation state

Robert Kukis
Prodigy 30 points
Part Number: LM5117

Tool/software:

Hello,

Regarding the LM5117 Synchronous Buck Controller, I would like a complete definition / more details of : ... the regulator may not start or it may hang up momentarily in a high power dissipation state.

Does a High Power dissipation state equate to the HO output being held High momentarily and the SW Output providing the maximum output Current momentarily?

My email address is : robert.kukis@rockwellautomation.com

Thank you for your help.

Good day.

rjk

  • 0
    TI__Intellectual 782 points

    Hi Robert

    Thanks for writing to us.

    High Power dissipation state doesn't mean HO being held high. Here is the more detail on high power dissipation state.

    For the proper operation of device and converter Vcc should be sufficiently high. If Vcc is not high enough device won't be able to turn on the high side FET, so device won't be able to start. Moreover, it is possible that  Vcc is high enough to turn on the FET but not completely. FET could operate in current saturation region leading to higher voltage drop across FET and thus more dissipation across the high side FET.

    Let me know if you any further query. Thank you

    Regards

    Onkar Bhakare

  • 0 in reply to Onkar Bhakare
    TI__Intellectual 782 points

    Could you please share minimum Vin in your application?